It's so awkward to act blasé about being naked around other people — people who are also, themselves, naked — that there's nothing left to do but submit en masse to the social and afferent novelty.
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Afferent is derived from Latin participle afferentem (af- = ad- : to + ferre : bear, carry), meaning carrying into. Ad and ex give an easy mnemonic device for remembering the relationship between afferent and efferent : afferent connection arrives and an efferent connection exits. Another mnemonic device used for remembering afferent and efferent (in terms of the spinal cord, with its dorsal/ventral organization) is SAME DAVE. Sensory Afferent Motor Efferent, Dorsal Afferent Ventral Efferent.
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Regular afferent signals and irregular afferent signals travel to the vestibular nuclei in the brain, although irregular signals are at least two times more sensitive. Because of this, it has been questioned why humans have regular afferent signals. Studies have shown that regular afferent signals give information about how long the motion of the head or body lasts, and irregular afferent signals occur when the head is moved more violently, such as in falling.
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The pupillary light reflex neural pathway on each side has an afferent limb and two efferent limbs. The afferent limb has nerve fibers running within the optic nerve (CN II). Each efferent limb has nerve fibers running along the oculomotor nerve (CN III). The afferent limb carries sensory input.
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Afferent and efferent are connected to affect and effect through their common Latin roots: Afferent nerves affect the subject, whereas efferent nerves allow the subject to effect change.
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Special somatic afferent fibers (SSA) are the afferent nerve fibers that carry information from the special senses of vision, hearing and balance. The cranial nerves containing SSA fibers are the optic nerve (II) and the vestibulocochlear nerve (VIII). The term "SSA" also encompasses both special somatic and special visceral afferent fibers.Drake et al.
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Specific terms are used for peripheral nerves that originate from, or arrive at, a specific point. An afferent nerve fiber is a fibre originating at the present point. For example, a striatal afferent is an afferent originating at the striatum. An efferent nerve fiber is one that arrives at the present point.
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Both afferent and efferent come from French, evolved from Latin (the basis of many terms in medicine and biology) for the terms, respectively, ad ferens (Latin verb ferre: carry), meaning carrying into, and ex ferens, meaning carrying away (ad literally means to, and e = ex means from). Ad and ex give an easy mnemonic device for remembering the relationship between afferent and efferent: afferent connection arrives and an efferent connection exits. Afferent and efferent are connected to affect and effect through their common Latin roots: Afferent nerves affect the subject, whereas efferent nerves allow the subject to effect change.
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The change in the architecture within the eye, from convex to concave, also explains why afferent nerves are located on the retina. It is due to the photo receptors retracting through the afferent nerves.
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The afferent nerve fibers of the olfactory receptor neurons transmit nerve impulses about odors to the central nervous system, where they are perceived as smell (olfaction). The olfactory nerve is special visceral afferent (SVA).
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The afferent arterioles are a group of blood vessels that supply the nephrons in many excretory systems. They play an important role in the regulation of blood pressure as a part of the tubuloglomerular feedback mechanism. The afferent arterioles branch from the renal artery, which supplies blood to the kidneys. The afferent arterioles later diverge into the capillaries of the glomerulus.
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Other afferent neurotransmitters include noradrenaline (from the brainstem), dopamine, serotonin, and acetylcholine.
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The peripheral nervous system with an enlarged depiction of an afferent neuron.
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Different physiological pathways may lead to shortness of breath including via ASIC chemoreceptors, mechanoreceptors, and lung receptors. It is thought that three main components contribute to dyspnea: afferent signals, efferent signals, and central information processing. It is believed the central processing in the brain compares the afferent and efferent signals; and dyspnea results when a "mismatch" occurs between the two: such as when the need for ventilation (afferent signaling) is not being met by physical breathing (efferent signaling). Afferent signals are sensory neuronal signals that ascend to the brain.
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Additionally, vasopressin selectively contracts efferent arterioles probably through the V1R, but not the afferent arteriole.
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Perl’s return to the University of Utah in 1963 marked the beginning of a research interest in primary afferent neurons, which evolved into a focus on nociceptors. Paul Bessou visited Perl’s laboratory and the two documented the activities of mechanoreceptive primary afferent neurons, whose thinly myelinated afferent fibers were responsive to non-noxious mechanical stimulation.Bessou P and Perl ER. A movement receptor of the small intestine. J. Physiol. (London) 182:404-426, 1966.
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The swinging-flashlight test is used to help a practitioner identify a relative afferent pupillary defect.
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Four types of sensory neuron Sensory neurons, also known as afferent neurons, are neurons in the nervous system, that convert a specific type of stimulus, via their receptors, into action potentials or graded potentials. This process is called sensory transduction. The cell bodies of the sensory neurons are located in the dorsal ganglia of the spinal cord. This sensory information travels along afferent nerve fibers in an afferent or sensory nerve, to the brain via the spinal cord.
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These cells are in contact with afferent fibers that are responsible for transmitting signals to the brain.
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Eliminating the gamma fusimotor drive prevents alteration in jaw muscle spindle afferent discharge following algesic chemical stimulation.
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In the CNS, afferent and efferent projections can be from the perspective of any given brain region. That is, each brain region has its own unique set of afferent and efferent projections. In the context of a given brain region, afferents are arriving fibers while efferents are exiting fibers.
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The mechanoreceptive hair cells of the lateral line structure are integrated into more complex circuits through their afferent and efferent connections. The synapses that directly participate in the transduction of mechanical information are excitatory afferent connections that utilize glutamate. However, a variety of different neuromast and afferent connections are possible, resulting in variation in mechanoreceptive properties. For instance, a series of experiments on the superficial neuromasts of Porichthys notatus revealed that neuromasts can exhibit a receptive specificity for particular frequencies of stimulation.
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Low-frequency afferent signals cause relaxation of the bladder by inhibiting sacral parasympathetic preganglionic neurons and exciting lumbar sympathetic preganglionic neurons. Conversely, afferent input causes contraction of the sphincter through excitation of Onuf's nucleus, and contraction of the bladder neck and urethra through excitation of the sympathetic preganglionic neurons. Diuresis (production of urine by the kidney) occurs constantly, and as the bladder becomes full, afferent firing increases, yet the micturition reflex can be voluntarily inhibited until it is appropriate to begin voiding.
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The solitary tract conveys afferent information from stretch receptors and chemoreceptors in the walls of the cardiovascular, respiratory, and intestinal tracts. Afferent fibers from cranial nerves 7, 9 and 10 convey taste (SVA) in its rostral portion, and general visceral sense (general visceral afferent fibers, GVA) in its caudal part. Taste buds in the mucosa of the tongue can also generate impulses in the rostral regions of the solitary tract. The efferent fibers are distributed to the solitary tract nucleus.
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The synapse between the afferent and efferent limbs occurs in the lowest sacral segments of the spinal cord.
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The afferent arterioles, then, enter Bowman's capsule and end in the glomerulus. From each glomerulus, the corresponding efferent arteriole arises and then exits the capsule near the point where the afferent arteriole enters. Distally, efferent arterioles branch out to form dense plexuses (i.e., capillary beds) around their adjacent renal tubules.
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Like other neurons, lower motor neurons have both afferent (incoming) and efferent (outgoing) connections. Alpha motor neurons receive input from a number of sources, including upper motor neurons, sensory neurons, and interneurons. The primary output of α-MNs is to extrafusal muscle fibers. This afferent and efferent connectivity is required to achieve coordinated muscle activity.
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An increase in the salt concentration causes several cell signals to eventually cause the adjacent afferent arteriole to constrict. This decreases the amount of blood coming from the afferent arterioles to the glomerular capillaries, and therefore decreases the amount of fluid that goes from the glomerular capillaries into the Bowman's space (the glomerular filtration rate (GFR)). When there is a decrease in the sodium concentration, less sodium is reabsorbed in the macular densa cells. The cells increase the production of nitric oxide and Prostaglandins to vasodilate the afferent arterioles and increase renin release.
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Just outside the spinal cord, thousands of afferent neuronal cell bodies are aggregated in a swelling in the dorsal root known as the dorsal root ganglion. All of the axons in the dorsal root, which contains afferent nerve fibers, are used in the transduction of somatosensory information. Somatosensory receptors include senses such as pain, touch, temperature, itch, and stretch. For example, a specific muscle fiber called an intrafusal muscle fiber is a type of afferent neuron that lies parallel to the extrafusal muscle fibers thus functions as a stretch receptor by detecting muscle length.
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It has been found that the percept elicited from a single tactile afferent in the glabrous skin of the hand, may be remarkably detailed and closely matching the properties of the afferent, indicating a high degree of specificity. Although this approach to bridge the gap between biophysical events in a single afferent and mental phenomena within the mind is simple and straight forward in principle it is demanding in practice for a number of reasons. Micro-stimulation has also been used to characterize individual motor units with regard to contraction properties.
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Elsevier Saunders, St. Louis, Mo, .Warrell D. A., Cox T. M., Firth J. D. (2010): The Oxford Textbook of Medicine (5th ed.). Oxford University Press In the CNS, afferent and efferent projections are determined from the perspective of any given brain region. That is, each brain region has its own unique set of afferent and efferent projections.
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A free nerve ending (FNE) or bare nerve ending, is an unspecialized, afferent nerve fiber sending its signal to a sensory neuron. Afferent in this case means bringing information from the body's periphery toward the brain. They function as cutaneous nociceptors and are essentially used by vertebrates to detect noxious stimuli that often result in pain.
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Somatosensory evoked potentials from the stimulation of both posterior nerve and median nerve are normal. The normal SEPs indicate that the RLS is related to abnormal sensorimotor integration. In 2010, Vincenzo Rizzo et al. provided evidence that RLS sufferers have lower than normal short latency afferent inhibition (SAI), inhibition of the motor cortex by afferent sensory signals.
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If both eyes are affected by PION, the pupils may look symmetrical. However, if the eyes are asymmetrically affected, i.e. one eye's optic nerve is more damaged than the other, it will produce an important sign called an afferent pupillary defect. Defective light perception in one eye causes an asymmetrical pupillary constriction reflex called the afferent pupillary defect (APD).
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These act on receptors on the afferent nerve fibres which lie in apposition to the glomus cell to cause an action potential.
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Perl ER. Myelinated afferent fibres innervating the primate skin and their response to noxious stimuli. J. Physiol. (London) 197: 593-615, 1968.
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Burgess PR and Perl ER. Myelinated afferent fibres responding specifically to noxious stimulation of the skin. J. Physiol. (London) 190: 541-562, 1967.
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The task-dependent fusimotor inputs codetermine spindle activity and, in turn, the complex central connectivity codetermines the functional use of spindle afferent signals.
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The work by Burgess and Perl represents the first thorough documentation of a large sample of nociceptors, primary afferent neurons that detect stimuli capable of causing tissue injury and transmit information about these insults centrally. (Previous work by Ainsley Iggo had provided a small sample of primary afferent fibers that are now understood to have been C-polymodal nociceptors.Iggo A. Cutaneous heat and cold receptors with slowly conducting (C) afferent fibres. Q. J. Exp. Physiol. Cogn. Med. Sci. 44: P362-P370, 1959.) Perl extended these studies to primate, showing the existence of high-threshold mechanoreceptors in squirrel monkey.
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A sensory nerve, also called an afferent nerve, is a nerve that carries sensory information toward the central nervous system (CNS) and all those nerves which can sense or recognise the stimulie (Internal or External) are known as sensory nerves. It is a cable-like bundle of the afferent nerve fibers coming from sensory receptors in the peripheral nervous system (PNS). A motor nerve carries information from the CNS to the PNS, and both types of nerve are called peripheral nerves. Afferent nerve fibers link the sensory neurons throughout the body, in pathways to the relevant processing circuits in the central nervous system.
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One of Unzer’s main contributions to science was the introduction of afferent and efferent reflexes. At its most basic level, afferent reflexes are those that move inward from something external, making its way to the central nervous system. Efferent then is the opposite, where the central nervous system triggers a reflex in the muscles. Unzer himself explains afferent reflexes: "To the end that an impression is felt…the external impression will have no other reflex action in the animal machines than that which is capable in virtue of its purely animal force, which it reflects upon the motor nerves…".
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A muscle spindle, with γ motor and Ia sensory fibers A type Ia sensory fiber, or a primary afferent fiber is a type of afferent nerve fiber. It is the sensory fiber of a stretch receptor found in muscles called the muscle spindle, which constantly monitors how fast a muscle stretch changes. (In other words, it monitors the velocity of the stretch).
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STD is a temporary jump in respiratory frequency at the beginning of carotid chemo afferent stimulation or a temporary drop in respiratory frequency at the end of chemo afferent stimulation. This mechanism lasts from a span of several seconds to a few minutes. STP has only been found in the respiratory frequency of phrenic nerve stimulation, which produces contraction of the diaphragm.
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Stimulation of the sacral nerve causes contraction of external sphincter and pelvic floor muscle, which in turn causes the inhibition of bladder contractions which may be involuntarily releasing urine. Researchers currently believe that the sacral neuromodulation blocks the c-afferent fibers, which are a critical part of the afferent limb of a pathological reflex arc believed to be responsible for incontinence.
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They contain Dogiel cells. The nerve bundles of the submucous plexus are finer than those of the myenteric plexus. Its function is to innervate cells in the epithelial layer and the smooth muscle of the muscularis mucosae. 14% of submucosal plexus neurons are sensory neurons - Dogiel type II, also known as enteric primary afferent neurons or intrinsic primary afferent neurons.
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Hair cells of the cristae activate afferent receptors in response to rotational acceleration. The other two sensory organs supplied by the vestibular neurons are the maculae of the saccule and utricle. Hair cells of the maculae in the utricle activate afferent receptors in response to linear acceleration while hair cells of the maculae in the saccule respond to vertically directed linear force.
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This lamina is only found in the cervical and lumbar regions of the spinal cord. It receives afferent input from muscle fibers and joints.
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The Ia afferent signal is also transmitted polysynaptically through interneurons (Ia inhibitory interneurons), which inhibit alpha motorneurons of antagonist muscles, causing them to relax.
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The longest lizard papillae are about 2mm long and contain 2000 hair cells and their afferent innervating fibers can be very sharply tuned to frequency.
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Neuroma formation and abnormal afferent nerve discharges after partial beak amputation (beak trimming) in poultry. Experientia, 41: 1132-1134Gentle, M.J. 1986. Beak trimming in poultry.
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The foot provides the sensory information to the central nervous system through cutaneous afferent feedback, which originates from the special mechanoreceptors within the plantar surface of the foot. This afferent feedback has a strong influence on postural stabilityMagnusson, M., Enbom, H., Johansson, R., Pyykko, I. Significance of pressor input from the human feet in anterior-posterior postural control, Acta. Otolaryngol. 110:182-188, 1990. and balance correctionR.
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The afferent component, also known as the track-and-trigger system, uses standardized tools to track early signs of reversible clinical deterioration and trigger a call to the efferent component. Examples of afferent tools include single-parameter calling criteria and multi-parameter early warning scores. These tools can predict clinical deterioration based upon the patient’s trait (e.g. has epilepsy) and detect deterioration through the patient’s state (e.g.
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The inflammatory reflex is a neural circuit that regulates the immune response to injury and invasion. All reflexes have an afferent and efferent arc. The Inflammatory reflex has a sensory, afferent arc, which is activated by cytokines, and a motor, or efferent arc, which transmits action potentials in the vagus nerve to suppress cytokine production. Increased signaling in the efferent arc inhibits inflammation and prevents organ damage.
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As a result of this reflex, activation of the Ib afferent causes the alpha motor neuron to become inhibited. Thus, the contraction of the muscle stops. This is an example of a disynaptic reflex, in which the circuitry contains a spinal interneuron between the sensory afferent and the motor neuron. The activities of the extensor and flexor muscles must be coordinated in the autogenic inhibition reflex.
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Vestibular afferent signals are carried by type I or type II hair cells, which are distinguished by a larger amount of stereocilia per cell in type I cells than in type II cells. Nerve fibers attached to these hair cells carry signals to the vestibular nuclei in the brain, which are then used to gain information about the body's position. Larger diameter afferent fibers carry information from both type I and type II hair cells, and regular afferent fibers carry signals from type II hair cells. The semicircular canals encode head velocity signals, or angular acceleration, while the otoconia encode linear acceleration signals and gravitational signals.
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The somatic nervous system (SNS or voluntary nervous system) is the part of the peripheral nervous system associated with the voluntary control of body movements via skeletal muscles. The somatic nervous system consists of afferent nerves or sensory nerves, and efferent nerves or motor nerves. Afferent nerves are responsible for relaying sensation from the body to the central nervous system; efferent nerves are responsible for sending out commands from the CNS to the body, stimulating muscle contraction; they include all the non-sensory neurons connected with skeletal muscles and skin. The a- of afferent and the e- of efferent correspond to the prefixes ad- (to, toward) and ex- (out of).
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The JGA is located between the thick ascending limb and the afferent arteriole. It contains three components: the macula densa, juxtaglomerular cells, and extraglomerular mesangial cells.
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Glucose is discussed in a later section. Afferent nerves carry signals back from the carotid and aortic bodies to the brainstem, which responds accordingly (e.g. increasing ventilation).
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Labeled diagram of human lymph node showing the flow of lymph. Afferent and efferent vessels Lymph enters the convex side of a lymph node through multiple afferent lymphatic vessels, which form a network of lymphatic vessels () and from here flows into a space () underneath the capsule called the subcapsular sinus. From here, lymph flows into sinuses within the cortex. After passing through the cortex, lymph then collects in medullary sinuses.
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From there, they contribute to the innervation of the pelvic and genital organs. The nerves regulate the emptying of the urinary bladder, control opening and closing of the internal urethral sphincter, influence motility in the rectum as well as sexual functions like erection. They contain both preganglionic parasympathetic fibers as well as visceral afferent fibers. Visceral afferent fibers go to spinal cord following pathway of pelvic splanchnic nerve fibers.
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When feedback regulation of afferent arteriolar tone is prevented by interrupting the feedback loop, and when the sensing mechanism is fully activated by saturating NaCl concentrations, TGF reduces GFR on average by approximately 45% and PGC by approximately 20%. Afferent arteriolar resistance increases by 50% or less, consistent with a radius reduction of approximately 10%, if Poiseuille's law holds. Thus, TGF-induced vasoconstriction is usually limited in magnitude.
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Philadelphia, PA : Lippincott Williams & Wilkins, c2013. This sensation, often conducted through skin and bone, is usually generated by mechanoreceptors such as Pacinian corpuscles, Merkel disk receptors, and tactile corpuscles. All of these receptors stimulate an action potential in afferent nerves (sensory neurons) found in various layers of the skin and body. The afferent neuron travels to the spinal column and then to the brain where the information is processed.
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J. Comp. Neurol. 186: 117-131, 1979.Light AR and Perl ER. Spinal termination of functionally identified primary afferent neurons with slowly conducting myelinated fibers. J. Comp. Neurol.
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These observations suggest that electrical stimulation may preferentially activate cutaneous afferent nerve fibers whereas magnetic stimulation may preferentially activate deeper nerves, such as the ulnar or median nerve.
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It is composed entirely of afferent fibers.Mondofacto Dictionary (definition of eponym) He converted to Catholicism in 1908 and is claimed to have written parts of The Protocols of Zion.
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The blood circulation in the periphery, especially the radiole, is especially unusual. Instead of venous and arterial blood flowing through afferent and efferent vessels within the radiole, there is a single branchial sinus through which blood flows in both directions, in a tidal fashion. The vessels of the peripheral system receive their blood from the central system, returning it back along the same channels (i.e., these channels serve in both afferent and efferent directions).
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As of 2017 little was understood about exactly how vagal nerve stimulation modulates mood and seizure control. The vagus is the tenth cranial nerve and arises from the medulla; it carries both afferent and efferent fibers. The afferent vagal fibers connect to the nucleus of the solitary tract which in turn projects connections to other locations in the central nervous system. Proposed mechanisms include an anti- inflammatory effect, as well as changes in monoamines.
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The microneurography electrode may be used not only for recording of nerve impulses but for stimulation of individual fibers as well. An interesting application is to combine successive recording and stimulation of the same afferent. Once the functional properties of an afferent have been defined, e.g. with regard to sensitivity, receptive field structure, and adaptation, the electrode may be reconnected to a stimulator to give trains of electrical pulses of controlled strength, rate, and duration.
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The autogenic inhibition reflex is a spinal reflex phenomenon that involves the Golgi tendon organ. When tension is applied to a muscle, group Ib fibers that innervate the Golgi tendon organ are activated. These afferent fibers project onto the spinal cord and synapse with the spinal interneurons called Ib inhibitory interneurons. This spinal interneuron makes an inhibitory synapse onto the alpha motor neuron that innervates the same muscle that caused the Ib afferent to fire.
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Hereby, he developed the hypothesis that the cerebral mechanisms controlling the movement of the hands interact within the brain with the afferent signal flow evoked in the mechanoreceptors while the grasping hand is moving across the surface of the object. The cerebral signals controlling the movement were called "Bewegidee" (motion idea). According to Steinbuch’s model, only by the interaction of the "Bewegidee" with the afferent signal flow did object recognition become possible.
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The auditory nerve fibres, known as the afferent nerve fibres, carry information from the organ of Corti to the brainstem and brain. Auditory afferent fibres consist of two types of fibres called type I and type II fibres. Type I fibres innervate the base of one or two inner hair cells and Type II fibres innervate the outer hair cells. Both leave the organ of Corti through an opening called the habenula perforata.
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Common coding posits, on top of separate coding, further domains of representation in which afferent and efferent information share the same format and dimensionality of representation. Common coding refers to 'late' afferent representations (referring to events in the environment) and 'early' efferent representations (referring to intended events). Such representations are commensurate since they both exhibit distal reference. They permit creating linkages between perception and action that do not rely on arbitrary mappings.
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Additionally, the mesolimbic pathway projects from the ventral tegmental area to the nucleus accumbens of the ventral striatum. Another well-known afferent is the nigrostriatal connection arising from the neurons of the substantia nigra pars compacta. While cortical axons synapse mainly on spine heads of spiny neurons, nigral axons synapse mainly on spine shafts. In primates, the thalamostriatal afferent comes from the central median-parafascicular complex of the thalamus (see primate basal ganglia system).
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The rest passes into an efferent arteriole. The diameter of the efferent arteriole is smaller than that of the afferent, and this difference increases the hydrostatic pressure in the glomerulus.
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Afferent nerves supplying the uterus are T11 and T12. Sympathetic supply is from the hypogastric plexus and the ovarian plexus. Parasympathetic supply is from the S2, S3 and S4 nerves.
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Special visceral afferent fibers (SVA) are the afferent fibers that develop in association with the gastrointestinal tract. They carry the special senses of smell (olfaction) and taste (gustation). The cranial nerves containing SVA fibers are the olfactory nerve (I), the facial nerve (VII), the glossopharyngeal nerve (IX), and the vagus nerve (X). The facial nerve receives taste from the anterior 2/3 of the tongue; the glossopharyngeal from the posterior 1/3, and the vagus nerve from the epiglottis.
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Regarding the afferent (input) connections to HSD2 neurons, available information is less complete. Experiments with conventional tracers and immunofluorescence staining have demonstrated peripheral viscerosensory input from the vagus nerve, input from nearby neurons in the NTS and area postrema, and descending input from the medial central nucleus of the amygdala (CeA) and paraventricular hypothalamic nucleus (PVN). It is likely that other sources of input exist, but a comprehensive study of HSD2 neuron afferent connections has not been conducted.
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Afferent neurons innervate cochlear inner hair cells, at synapses where the neurotransmitter glutamate communicates signals from the hair cells to the dendrites of the primary auditory neurons. There are far fewer inner hair cells in the cochlea than afferent nerve fibers – many auditory nerve fibers innervate each hair cell. The neural dendrites belong to neurons of the auditory nerve, which in turn joins the vestibular nerve to form the vestibulocochlear nerve, or cranial nerve number VIII.Meddean – CN VIII.
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The afferent lymph vessels enter at all parts of the periphery of the lymph node, and after branching and forming a dense plexus in the substance of the capsule, open into the lymph sinuses of the cortical part. It carries unfiltered lymph into the node. In doing this they lose all their coats except their endothelial lining, which is continuous with a layer of similar cells lining the lymph paths. Afferent lymphatic vessels are only found in lymph nodes.
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Adachi A., Shimizu N., Oomura Y., Kobashi M. - Convergence of hepatoportal glucose-sensitive afferent signals to glucose-sensitive units within the nucleus of the solitary tract. Neuroscience Letters, 1984 46, 215-218.
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C fibers are one class of nerve fiber found in the nerves of the somatic sensory system. They are afferent fibers, conveying input signals from the periphery to the central nervous system.
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Catecholamines (norepinephrine and epinephrine) increase filtration fraction by vasoconstriction of afferent and efferent arterioles, possibly through activation of alpha-1 adrenergic receptors. Severe haemorrhage will also result in an increased filtration fraction.
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A brush cell is a microvilli-bearing columnar cell with its basal surface in contact with afferent nerve endings of the trigeminal nerve (CN V) and is specialized for transduction of general sensation.
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The walls of the afferent arteriole contain specialized smooth muscle cells that synthesize renin. These juxtaglomerular cells play a major role in the renin–angiotensin system, which helps regulate blood volume and pressure.
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The hilum is an indent on the concave surface of the lymph node where lymphatic vessels leave and blood vessels enter and leave. Lymph enters the convex side of a lymph node through multiple afferent lymphatic vessels and from here flows into a series of sinuses. After entering the lymph node from afferent lymphatic vessels, lymph flows into a space underneath the capsule called the subcapsular sinus, then into cortical sinuses. After passing through the cortex, lymph then collects in medullary sinuses.
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An alternative "fresh afferent" interpretation is that there are no memory neuronal elements, but the sensory afferent neuronal elements that are tuned to properties of the standard stimulation respond less vigorously upon repeated stimulation. Thus when a deviant activates a distinct new population of neuronal elements that is tuned to the different properties of the deviant rather than the standard, these fresh afferents respond more vigorously, eliciting an MMN. A third view is that the sensory afferents are the memory neurons.
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Afferent nerve fibers refer to axonal projections that arrive at a particular brain region, as opposed to efferent projections that exit the region. These terms have a slightly different meaning in the context of the peripheral nervous system (PNS) and central nervous system (CNS). In the PNS, afferent and efferent projections are always from the perspective of the spinal cord (see figures). PNS afferents are the axons of sensory neurons carrying sensory information from all over the body, into the spine.
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Others involve lower brain areas and can be influenced by prior instructions or intentions, but they remain independent of perceptual processing and online control. The simplest reflex is the monosynaptic reflex or short-loop reflex, such as the monosynaptic stretch response. In this example, Ia afferent neurons are activated by muscle spindles when they deform due to the stretching of the muscle. In the spinal cord, these afferent neurons synapse directly onto alpha motor neurons that regulate the contraction of the same muscle.
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The middle peduncle is the largest of the three and its afferent fibers are grouped into three separate fascicles taking their inputs to different parts of the cerebellum. The inferior cerebellar peduncle receives input from afferent fibers from the vestibular nuclei, spinal cord and the tegmentum. Output from the inferior peduncle is via efferent fibers to the vestibular nuclei and the reticular formation. The whole of the cerebellum receives modulatory input from the inferior olivary nucleus via the inferior cerebellar peduncle.
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Although the anterior two thirds of the tongue are derived from the first pharyngeal arch, which gives rise to the facial nerve, not all innervation of the tongue is supplied by it. The lingual branch of the mandibular division (V3) of the trigeminal nerve supplies non-taste sensation (pressure, heat, texture) to the anterior part of the tongue via general visceral afferent fibers. Nerve fibers for taste are supplied by the chorda tympani branch of the facial nerve via special visceral afferent fibers.
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The facial nerve carries axons of type GSA, general somatic afferent, to skin of the posterior ear. The facial nerve also carries axons of type GVE, general visceral efferent, which innervate the sublingual, submandibular, and lacrimal glands, also mucosa of nasal cavity. Axons of type SVE, special visceral efferent, innervate muscles of facial expression, stapedius, the posterior belly of digastric, and the stylohyoid. The axons of type SVA, special visceral afferent, provide taste to the anterior two-thirds of tongue via chorda tympani.
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The term retinotopic refers to the maintenance of the particular order of afferent connections from the retina along the afferent pathway via sub-cortical structures to V1 and other cortical visual areas. The primary visual cortex (V1, Brodmann's area 17) is the first cortical area to receive visual input. The stria of Gennari – a set of heavily myelinated, horizontally projecting axons within the termination zone of lateral geniculate nucleus (LGN) input to V1 – provides an anatomical marker particular to V1.
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They also contain general visceral afferent fibers. They are found in the same region as the pelvic splanchnic nerves, which arise from the sacral spinal nerves to provide parasympathetic fibers to the inferior hypogastric plexus.
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Cutaneous receptors are at the ends of afferent neurons. They are usually encapsulated in elaborate cellular corpuscles. Generally, they are linked to collagen - fibres networks within the capsule. Ion channels are situated near these networks.
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These disturbances can be described by a series of several key events. First and foremost, repetitive muscle exercise can lead to the development of fatigue due to one or more of the following: inadequate conditioning, hot and or humid environments, increased intensity, increased duration, and decreased supply of energy. Muscle fatigue itself causes increased excitatory afferent activity within the muscle spindles and decreased inhibitory afferent activity within the Golgi tendon. The coupling of these events leads to altered neuromuscular control from the spinal cord.
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Kidneys of common ravens receive arterial and afferent venous blood and are drained by efferent veins. In terms of the arterial blood supply, the arteries entering the kidneys branch into numerous smaller arteries and eventually form afferent arterioles that supply the glomeruli. The peritubular blood supply is composed of efferent arterioles leaving the glomeruli of reptilian-type nephrons that drain into sinuses of the cortex. On the other hand, the vasa recta are formed by efferent arterioles exiting the glomeruli of mammalia-type nephrons.
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This results in a shift in the cell's ionic permeability, resulting from changes to open ion channels caused by the deflection of the hairs. Deflection towards the longest hair results in depolarization of the hair cell, increased neurotransmitter release at the excitatory afferent synapse, and a higher rate of signal transduction. Deflection towards the shorter hair has the opposite effect, hyperpolarizing the hair cell and producing a decreased rate of neurotransmitter release. These electrical impulses are then transmitted along afferent lateral neurons to the brain.
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General model for cross-talk between afferent signaling pathways, coregulators and nuclear receptors at a promoter showing local nucleosomal condensation.A spectrum of post-translational modifications is known to regulate the functional relationships between nuclear receptors, their coregulator complexes, and their target gene networks. Targeted, reversible enzymatic modifications such as acetylation, methylation phosphorylation and terminal modifications such as ubiquitination have been shown to have a variety of effects on coregulator function. Coregulators may be viewed as control interfaces for integrating multiple afferent stimuli into an appropriate cellular response.
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In the human brain, the superior cerebellar peduncle (brachium conjunctivum) is a paired structure of white matter that connects the cerebellum to the midbrain. It consists mainly of efferent fibers, the cerebellothalamic tract that runs from a cerebellar hemisphere to the contralateral thalamus, and the cerebellorubral tract that runs from a cerebellar hemisphere to the red nucleus. It also contains afferent tracts, most prominent of which is the ventral spinocerebellar tract. Other afferent tracts are the trigeminothalamic fibers, tectocerebellar fibers, and noradrenergic fibers from the locus coeruleus.
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The sympathetic ganglia, or autonomic ganglia, are the ganglia of the sympathetic nervous system. Ganglia are 20,000 to 30,000 afferent and efferent nerve cell bodies that run along on either side of the spinal cord. Afferent nerve cell bodies bring information from the body to the brain and spinal cord, while efferent nerve cell bodies bring information from the brain and spinal cord to the rest of the body. The cell bodies create long sympathetic chains that are on either side of the spinal cord.
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4th ed. New York: Marcel Dekker; 2004. The fundamental role of the OHCs and the IHCs is to function as sensory receptors. The main function of the IHCs is to transmit sound information via afferent neurons.
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He specialized in neurophysiology. He took the cand.med. degree in 1955, and in 1957 he took the dr.med. degree with the thesis Afferent impulses to the cerebellar hemispheres from the cerebral cortex and certain subcortical nuclei.
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The Ib afferent branches in the spinal cord. One branch synapses the Ib inhibitory interneuron. The other branch synapses onto an excitatory interneuron. This excitatory interneuron innervates the alpha motor neuron that controls the antagonist muscle.
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This increase in intracellular calcium activates the TRPM5 channel and induces cellular depolarization. The ATP release channel CALHM1 gets activated by the depolarization and releases ATP neurotransmitter which activates the afferent neurons innervating the taste bud.
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Drawing of cerata of Fiona pinnata. There are small afferent (leading into heart) vessels in cerata with puckered membranous fringe on the inner sides. The vessels are leading to great median trunk and to the heart.
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Thoracic splanchnic nerves are splanchnic nerves that arise from the sympathetic trunk in the thorax and travel inferiorly to provide sympathetic innervation to the abdomen. The nerves contain preganglionic sympathetic fibers and general visceral afferent fibers.
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The opposite direction of neural activity is afferent conduction,Mader S. S. (2000): Human biology. McGraw-Hill, New York, ; .Hall J. E., Guyton A. C. (2006): Textbook of medical physiology, 11th edition. Elsevier Saunders, St. Louis, Mo, .
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The ventral anterior nucleus receives neuronal inputs from the basal ganglia. Its main afferent fibres are from the globus pallidus. The efferent fibres from this nucleus pass into the premotor cortex for initiation and planning of movement.
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Neuroma formation and abnormal afferent nerve discharges after partial break amputation (beak trimming) in poultry. Experientia, 41: 1132-1134. Neuromas, tangled masses of swollen regenerating axon sprouts,Devor, M. and Rappaport, Z.H., (1990). Pain Syndromes in Neurology.
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A motor program is an abstract representation of movement that centrally organizes and controls the many degrees of freedom involved in performing an action.p. 182 Signals transmitted through efferent and afferent pathways allow the central nervous system to anticipate, plan or guide movement. Evidence for the concept of motor programs include the following:p. 182 :# Processing of afferent information (feedback) is too slow for on-going regulation of rapid movements. :# Reaction time (time between “go” signal and movement initiation) increases with movement complexity, suggesting that movements are planned in advance.
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Oxytocin and vasopressin can, thus, be released within the brain from these dendrites, as well as into the blood from the terminals in the posterior pituitary gland. However, the release of oxytocin and vasopressin from dendrites is not consistently accompanied by peripheral secretion, as dendritic release is regulated differently. Dendritic release can be triggered by depolarisation, but can also be triggered by the mobilisation of intracellular calcium stores. The dendrites receive most of the synaptic inputs from afferent neurons that regulate the magnocellular neurons; typically a magnocellular neuron receives about 10,000 synapses from afferent neurons.
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Injury to sensory nerves induces neurochemical, physiological, and anatomical modifications to afferent and central neurons, such as afferent terminal sprouting and inhibitory interneuron loss. Following nerve damage, NaCl channel accumulation causes hyperexcitability, and downregulation of the TTX-resistant Nav1.8 (sensory neuron specific, SNS1) channel and upregulation of TTX-sensitive Nav1.3 (brain type III) and TRPV1 channels. These changes contribute to increased NMDA glutamate receptor-dependent excitability of spinal dorsal horn neurons and are restricted to the ipsilateral (injured) side. A combination of these factors could contribute to the neuropathic pain state of postherpetic neuralgia.
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The neurons in the inferior ganglion of the vagus nerve are pseudounipolar and provide sensory innervation (general somatic afferent and general visceral afferent). The axons of the neurons which innervate the taste buds of the epiglottis synapse in the rostral portion of the solitary nucleus (gustatory nucleus). The axons of the neurons which provide general sensory information synapse in the spinal trigeminal nucleus. The axons of the neurons which innervate the aortic bodies, aortic arch, respiratory and gastrointestinal tract, synapse in the caudal part of the solitary nucleus.
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Due to the environment to which it is exposed, the posterior gills of the crab can also be cleared of parasites and sediment by increasing the movement of its fifth set of primitive legs. Each gill has a main axis with many lateral filaments or lamellae that are vascularized. The afferent channel transports blood from the gill axis into each filament through a fine afferent canal to the gill top. Blood returns by a minute efferent canal to the gill tip to the efferent channel and passes to the pericardial chamber, which contains the heart.
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When the afferent and efferent nerves are both destroyed, as they may be by tumors of the cauda equina or filum terminale, the bladder is flaccid and distended for a while. Gradually, however, the muscle of the "decentralized bladder" becomes active, with many contraction waves that expel dribbles of urine out of the urethra. The bladder becomes shrunken and the bladder wall hypertrophied. The reason for the difference between the small, hypertrophic bladder seen in this condition and the distended, hypotonic bladder seen when only the afferent nerves are interrupted is not known.
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The state of the reflex system is dependent on both a conscious signal from the brain and the firing rate of sensory fibers from the bladder and urethra. At low bladder volumes, afferent firing is low, resulting in excitation of the outlet (the sphincter and urethra), and relaxation of the bladder. At high bladder volumes, afferent firing increases, causing a conscious sensation of urinary urge. When the individual is ready to urinate, he or she consciously initiates voiding, causing the bladder to contract and the outlet to relax.
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Urinating woman Urinating man Voiding begins when a voluntary signal is sent from the brain to begin urination, and continues until the bladder is empty. Bladder afferent signals ascend the spinal cord to the periaqueductal gray, where they project both to the pontine micturition center and to the cerebrum. At a certain level of afferent activity, the conscious urge to void becomes difficult to ignore. Once the voluntary signal to begin voiding has been issued, neurons in pontine micturition center fire maximally, causing excitation of sacral preganglionic neurons.
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The macula densa is a collection of densely packed epithelial cells at the junction of the thick ascending limb (TAL) and distal convoluted tubule (DCT). As the TAL ascends through the renal cortex, it encounters its own glomerulus, bringing the macula densa to rest at the angle between the afferent and efferent arterioles. The macula densa's position enables it to rapidly alter afferent arteriolar resistance in response to changes in the flow rate through the distal nephron. The macula densa uses the composition of the tubular fluid as an indicator of GFR.
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The peripheral nervous system is composed of afferent and efferent neurons; disorder of these neurons is called peripheral neuropathy. Vibration examination can detect and localize disorders of the peripheral nervous system. A gradual loss of sensation from the toes to the knees is consistent with a peripheral nerve problem, whereas an impairment in perceiving vibration from all extremities is a sign of a posterior column disorder. Impairments classified to the peripheral nervous system and posterior column are indicators of demyelination of afferent neurons from a variety of causes.
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They are static, whereas the nuclear bag fibers are dynamic in comparison. The name "nuclear chain" refers to the structure of the central region of the fiber, where the sensory axons wrap around the intrafusal fibers. The secondary nerve association involves an efferent and afferent pathway that measure the stress and strain placed on the muscle (usually the extrafusal fibers connected from the muscle portion to a bone). The afferent pathway resembles a spring wrapping around the nuclear chain fiber and connecting to one of its ends away from the bone.
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Yelnik, J., Percheron, G., and François, C. (1984) A Golgi analysis of the primate globus pallidus. II- Quantitative morphology and spatial orientation of dendritic arborisations. J. Comp. Neurol. 227:200–213 and perpendicular to the afferent striatopallidal axons.
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The optic disc is also the entry point for the major blood vessels that supply the retina. The optic disc in a normal human eye carries 1–1.2 million afferent nerve fibers from the eye towards the brain.
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Joint stability can be enhanced by the use of an external support system, like a brace, to alter body mechanics. The mechanical support provided by a brace provides cutaneous afferent feedback in maintaining postural control and increasing stability.
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This afferent is glutamatergic. The participation of truly intralaminar neurons is much more limited. The striatum also receives afferents from other elements of the basal ganglia such as the subthalamic nucleus (glutamatergic) or the external globus pallidus (GABAergic).
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The somatosensory system is spread through all major parts of the vertebrate body. It consists both of sensory receptors and afferent neurons in the periphery (skin, muscle and organs for example), to deeper neurons within the central nervous system.
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Tree of Life web project. They pump blood through the gills via the afferent branchial veins. Since they only circulate venous blood, branchial hearts function under predominantly anaerobic conditions. Branchial hearts also appear to be involved in hemocyanin synthesis.
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Unlike the thalamus, which has broad reciprocal connectivity, cortical projections with the putamen are afferent, thus sending information as opposed to receiving it. Cortical communication is accomplished via multi- fiber pathways as outlined previously (i.e. via other subcortical structures).
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The juxtarestiform body carries both afferent and efferent fibers connecting the vestibular nuclei and the flocculonodular lobe and fastigial nucleus of the cerebellum. The juxtarestiform body coordinates balance and eye movements by communication between the vestibular apparatus and the cerebellum.
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At the vascular pole, the afferent arterioles and efferent arterioles enter and leave the glomerulus in the Bowman's capsule. The tubular pole is at the other end opposite to the vascular pole. At the tubular pole, the proximal convoluted tubule arises.
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This can result in deafferentation, which means the development of different central processes from the surviving afferent nerve. With this situation, surviving dorsal root axons of the nociceptors can make contact with the spinal cord, thus changing the normal input.
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Combining these two fMRI studies, one could hypothesize that the alien behavior that is unaccompanied by a sense of agency emerges due to autonomous activity in the primary motor cortex acting independently of premotor cortex pre-activating influences that would normally be associated with the emergence of a sense of agency linked to the execution of the action. As noted above, these ideas can also be linked to the concept of efference copy and re-afference, where efference copy is a signal postulated to be directed from premotor cortex (activated normally in the process associated with emergence of an internally generated movement) over to somatosensory cortex of the parietal region, in advance of the arrival of the "re-afferent" input generated from the moving limb, that is, the afferent return from the moving limb associated with the self-generated movement produced. It is generally thought that a movement is recognized as internally generated when the efference copy signal effectively "cancels out" the re-afference. The afferent return from the limb is effectively correlated with the efference copy signal so that the re-afference can be recognized as such and distinguished from "ex-afference", which would be afferent return from the limb produced by an externally imposed force.
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The juxtaglomerular cells in the afferent arteriole constrict, and juxtaglomerular cells in both the afferent and efferent arteriole decrease their renin secretion. These actions function to lower GFR. Further increase in sodium concentration leads to the release of nitric oxide, a vasodilating substance, to prevent excessive vasoconstriction. In the opposite case, juxtaglomerular cells are stimulated to release more renin, which stimulates the renin–angiotensin system, producing angiotensin I which is converted by Angio- Tensin Converting Enzyme (ACE) to angiotensin II. Angiotensin II then causes preferential constriction of the efferent arteriole of the glomerulus and increases the GFR.
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Targeted reinnervation has an efferent and an afferent component. Targeted muscle reinnervation is a method by which a spare muscle (the target muscle) of an amputated patient is denervated (its original nerves cut and/or de-activated), then reinnervated with residual nerves of the amputated limb. The resultant EMG signals of the targeted muscle now represent the motor commands to the missing limb, and are used to drive a motorized prosthetic device. Targeted sensory reinnervation is a method by which skin near or over the targeted muscle is denervated, then reinnervated with afferent fibers of the remaining hand nerves.
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Garraway explored how primary afferent stimulation impacted plasticity, in the form of long term potentiation (LTP) or long term depression (LTD), of the DDH neurons. LTP and LTD had only just been identified in the spinal cord, and Garraway discovered that LTP and LTD can also be induced in the DDH neurons with even lower frequency afferent stimulation. She also found that in rats aged P9-16, only LTP could be produced. These findings shed light on potential mechanisms of prolonged pain sensation, or chronic pain, as LTD and LTP present forms of long lasting cellular memory.
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Cold-patches have traditionally been used to induce analgesia or relief in pain which is caused as result of traumatic injuries. The underlying mechanism of cold-induced analgesia remained obscure until the discovery of TRPM8. One research group has reported that TRPM8 is activated by chemical cooling agents (such as menthol) or when ambient temperatures drop below approximately 26 °C, suggesting that it mediates the detection of cold thermal stimuli by primary afferent sensory neurons of afferent nerve fibers. Three independent research groups have reported that mice lacking functional TRPM8 gene expression are severely impaired in their ability to detect cold temperatures.
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In hypertension only the afferent arteriole is affected, while in diabetes mellitus, both the afferent and efferent arteriole are affected. ;Cause Lesions reflect leakage of plasma components across vascular endothelium and excessive extracellular matrix production by smooth muscle cells, usually secondary to hypertension. Hyaline arteriolosclerosis is a major morphologic characteristic of benign nephrosclerosis, in which the arteriolar narrowing causes diffuse impairment of renal blood supply, with loss of nephrons. The narrowing of the lumen can decrease renal blood flow and hence glomerular filtration rate leading to increased renin secretion and a perpetuating cycle with increasing blood pressure and decreasing kidney function.
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Coughing is a mechanism of the body that is essential to normal physiological function of clearing the throat which involves a reflex of the afferent sensory limb, central processing centre of the brain and the efferent limb. In conjunction to the components of the body that are involved, sensory receptors are also used. These receptors include rapidly adapting receptors which respond to mechanical stimuli, slowly adapting receptors and nociceptors which respond to chemical stimuli such as hormones in the body. To start the reflex, the afferent impulses are transmitted to the medulla of the brain this involves the stimulus which is then interpreted.
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Staging of chronic kidney disease is based on categories of GFR as well as albuminuria and cause of kidney disease. Central to the physiologic maintenance of GFR is the differential basal tone of the afferent and efferent arterioles (see diagram). In other words, the filtration rate is dependent on the difference between the higher blood pressure created by vasoconstriction of the input or afferent arteriole versus the lower blood pressure created by lesser vasoconstriction of the output or efferent arteriole. GFR is equal to the renal clearance ratio when any solute is freely filtered and is neither reabsorbed nor secreted by the kidneys.
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This results in a smaller capillary hydrostatic pressure, which causes an increased absorption of sodium ions into the vasa recta at the proximal tubule. Hence, a decrease in blood pressure results in less sodium chloride present at the distal tubule, where the macula densa is located. The macula densa senses this drop in salt concentration and responds through two mechanisms, both of which are mediated by prostaglandin release. First, prostaglandins preferentially vasodilate the renal afferent arteriole, decreasing afferent arteriole resistance and, thus, offsetting the decrease in glomerular hydrostatic pressure caused by the drop in blood pressure.
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The process triggered by the macula densa helps keep the GFR fairly steady in response to varying artery pressure. Damage to the macula densa would impact blood flow to the kidneys because the afferent arterioles would not dilate in response to a decrease in filtrate osmolarity and pressure at the glomerulus would not be increased. As part of the body's blood pressure regulation, the macula densa monitors filtrate osmolarity; if it falls too far, the macula densa causes the afferent arterioles of the kidney to dilate, thus increasing the pressure at the glomerulus and increasing the glomerular filtration rate.
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The hepatic venous pressure gradient, (difference in venous pressure between afferent and efferent blood to the liver) also determines the severity of cirrhosis, although it is hard to measure. A value of 16 mm or more means a greatly increased risk of death.
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Afferent nerve fibers are often paired with efferent nerve fibers from the motor neurons (that travel from the CNS to the PNS), in mixed nerves. Stimuli cause nerve impulses in the receptors and alter the potentials, which is known as sensory transduction.
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Afferents responding to noxious stimuli are known as nociceptors. There are 2 main groups, unmyelinated C-afferents and small myelinated Aδ fibers. Most studies are focused on C nociceptiors. The nociceptive C-fibers constitute a very large proportion of somatic afferent nerve fibers.
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The inferior brachium carries auditory afferent fibers from the inferior colliculus of the mesencephalon to the medial geniculate nucleus.Neuroanatomy 5th edition, Nolte. Mosby 2002. The inferior colliculus receives input from both the ipsilateral and contralateral cochlear nucleus and respectively the corresponding ears.
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The facial nerve also supplies a small amount of afferent innervation to the oropharynx below the palatine tonsil. There is also a small amount of cutaneous sensation carried by the nervus intermedius from the skin in and around the auricle (outer ear).
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Baroreflex activation is distinct from vagal stimulation. It works through an afferent limb which has the double effect of stimulating vagal outflow and attenuating global sympathetic outflow. The baroreflex can be used to treat resistant hypertension. This stimulation is provided by a pacemaker-like device.
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The juxtaglomerular apparatus is part of the kidney nephron, next to the glomerulus. It is found between afferent arteriole and the distal convoluted tubule of the same nephron. This location is critical to its function in regulating renal blood flow and glomerular filtration rate.
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Extraglomerular mesangial cells are located in the junction between the afferent and efferent arterioles. These cells have a contractile property similar to vascular smooth muscles and thus play a role in “regulating GFR” by altering the vessel diameter. Renin is also found in these cells.
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Activation of KORs on peripheral nerve terminals results in the inhibition of ion channels responsible for afferent nerve activity, causing reduced transmission of pain signals, while activation of KORs expressed by immune system cells results in reduced release of proinflammatory, nerve-sensitizing mediators (e.g., prostaglandins).
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In medicine, the colloquial term "touch" is usually replaced with "somatic senses" to better reflect the variety of mechanisms involved. Insensitivity to somatosensory stimuli, such as heat, cold, touch, and pain, are most commonly a result of a more general physical impairment associated with paralysis. Damage to the spinal cord or other major nerve fiber may lead to a termination of both afferent and efferent signals to varying areas of the body, causing both a loss of touch and a loss of motor coordination. Other types of somatosensory loss include hereditary sensory and autonomic neuropathy, which consists of ineffective afferent neurons with fully functioning efferent neurons; essentially, motor movement without somatosensation.
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Micro-stimulation has shown that input from one single Meissner, Merkel, or Pacini unit may produce a distinct and differential percept in the mind of the subject indicating an absolute specificity within the tactile system. It has even been demonstrated that a single impulse in a Meissner afferent may produce a percept. In contrast, no percept is reported when a single Ruffini afferent is stimulated which might indicate that spatial summation is required. Consistent with the perceptive findings, neural responses in the somatosensory cortex have been recorded on micro-stimulation of single afferents connected to Meissner, Merkel, Pacini endings but not with single Ruffini afferents.
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Firstly, they demonstrated the cutaneous distribution in man of each afferent root, a valuable aid to the localisation of diseases of the spinal cord and its roots. Secondly, they revealed the mechanism of 'referred pain' so often associated with visceral disease. What they found was that many herpetic areas representing the peripheral distribution of single roots or individual sections of the cord, corresponded closely with areas of referred pain from diseases of different internal organs. This led Head to conclude that irradiation of abnormal afferent impulses produces a state of excessive irritability in the grey matter of the dorsal horn at the level which they enter it.
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The vestibulocochlear nerve is accompanied by the labyrinthine artery, which usually branches off from the anterior inferior cerebellar artery (AICA) at the cerebellopontine angle, and then goes with the 7th nerve through the internal acoustic meatus to the internal ear. The cochlear nerve travels away from the cochlea of the inner ear where it starts as the spiral ganglia. Processes from the organ of Corti conduct afferent transmission to the spiral ganglia. It is the inner hair cells of the organ of Corti that are responsible for activation of afferent receptors in response to pressure waves reaching the basilar membrane through the transduction of sound.
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The nucleus raphe pallidus receives afferent connections from the periaqueductal gray, the Paraventricular nucleus of hypothalamus, central nucleus of the amygdala, lateral hypothalamic area, and parvocellular reticular nucleus. Also, the nucleus raphe pallidus receives afferents from the medial preoptic area, median preoptic nucleus and lateral paragigantocellular reticular nuclei.Hermann, Dirk M. et al. Afferent projections to the rat nuclei raphe magnus, raphe pallidus and reticularis gigantocellularis pars demonstrated by iontophoretic application of choleratoxin (subunit b). Journal of Chemical Neuroanatomy Volume 13, Issue 1, June 1997, Pages 1-21 The nucleus raphe pallidus has recently been shown to be involved in the activation of a fever as an immunoreaction.
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Sensory afferent nerves trigger a systemic sympathetic activation leading to marked vasoconstriction. The result is an elevated pulse pressure (normal is 40mm Hg), due to catecholamine release. This increased pressure fills the ventricle to a greater extent, but stroke volume decreases due to an increase in afterload.
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The carotid body functions as a sensor: it responds to a stimulus, primarily O2 partial pressure, which is detected by the type I (glomus) cells, and triggers an action potential through the afferent fibers of the glossopharyngeal nerve, which relays the information to the central nervous system.
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Kumazawa T and Perl ER, Primary cutaneous sensory units with unmyelinated (C) afferent fibers. J. Neurophysiol. 40: 1325-1338, 1977.Kumazawa T and Perl ER. Excitation of marginal and substantia gelatinosa neurons in the primate spinal cord: indications of their place in dorsal horn functional organization.
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Afferent nerve fibers leave the sensory neuron from the dorsal root ganglia of the spinal cord, and motor commands carried by the efferent fibers leave the cord at the ventral roots. The dorsal and some of the ventral fibers join as spinal nerves or mixed nerves.
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In somatosensory transduction, the afferent neurons transmit messages through synapses in the dorsal column nuclei, where second-order neurons send the signal to the thalamus and synapse with third-order neurons in the ventrobasal complex. The third-order neurons then send the signal to the somatosensory cortex.
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Expression of Nav1.9 in the afferent neurons of the dorsal root ganglion was found to be elevated as many as four weeks after the onset of the inflammatory pain. These results indicated that this alpha subunit plays some role in the maintenance of chronic inflammatory pain.
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Science, 167: 1745–1748Fischer, T.M., Jacobson, D.A., Counsell, A.N., et al., (2011). Regulation of low-threshold afferent activity may contribute to short-term habituation in Aplysia californica. Neurobiology of Learning and Memory, 95: 248-259 Mollusk neurons are able to detect increasing pressures and tissue trauma.
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This scorpion toxin was named WaTx because it targets TRPA1 in a similar fashion as plant-derived irritants, such as mustard oil and wasabi. These irritants activate the TRPA1 channel in peripheral primary afferent sensory neurons, subsequently eliciting their pungent taste as well as sinus clearing and eye stinging.
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Often tumor cells secrete growth factors which activate receptors close to primary afferent neurons. Activation of these neural receptors is a contributing factor to pain sensation. Additionally, inflammatory lipids called prostaglandins, which are produced at high rates by cancer cells within tumors, activate nociceptors when they bind together.
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Hyperpathia describes the neuropathic pain which the pain threshold on one hand is elevated and the other hand is central hyperexcited whenever there is a loss of fibres. Hyperpathia is underlying the peripheral or central deafferentation when the afferent inputs are lost.Jensen, T. S. (1996). Mechanisms of neuropathic pain.
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A spinal interneuron, found in the spinal cord, relays signals between (afferent) sensory neurons, and (efferent) motor neurons. Different classes of spinal interneurons are involved in the process of sensory-motor integration. Most interneurons are found in the grey column, a region of grey matter in the spinal cord.
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Some afferent decussations. Pyramidal decussations. Anatomically, the contralateral organization is manifested by major decussations (latin: the Latin notation for ten, 'deca', is an uppercase 'X') and chiasmas (after the Greek uppercase letter 'Χ', chi). A decussation denotes a crossing of bundles of axonal fibres inside the central nervous system.
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In 1954 Perl accepted a faculty position at the State University of New York, College of Medicine, Syracuse (now known as SUNY Upstate Medical University), where he not only researched crossed spinal reflexes, but also renewed his interest in the activity of C-fiber afferent fibers and their projections to the spinal cord. Perl left SUNY-Syracuse in 1957 to join the University of Utah’s Department of Physiology, then led by neurophysiologist Carlton C. Hunt. Perl’s work at Utah focused on spinothalamic somatosensory pathways and the interactions between primary afferent neurons and spinal dorsal column nuclei. Beginning in 1962, Perl spent a year in Yves Laporte's laboratory at the Faculté de Médecine in Toulouse, France.
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In the mid-1970s Alan R. Light, Miklós Réthelyi, and Daniel Trevino joined Perl's laboratory to further map the central terminations of thinly-myelinated primary afferent neurons, to study their synaptic morphologies, and to characterize neurons in the dorsal horn of the spinal cord that were responsive to activity of these fibers.Light AR and Perl ER. Differential termination of large-diameter and small-diameter primary afferent fibers in the spinal dorsal gray matter as indicated by labeling with horseradish peroxidase. Neurosci. Lett. 6: 59-63, 1977.Light AR and Perl ER. Reexamination of the dorsal root projection to the spinal dorsal horn including observations on the differential termination of coarse and fine fibers.
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As the light is being moved from one eye to another, both eyes begin to dilate, but constrict again when light has reached the other eye. If there is an efferent defect in the left eye, the left pupil will remain dilated regardless of where the light is shining, while the right pupil will respond normally. If there is an afferent defect in the left eye, both pupils will dilate when the light is shining on the left eye, but both will constrict when it is shining on the right eye. This is because the left eye will not respond to external stimulus (afferent pathway), but can still receive neural signals from the brain (efferent pathway) to constrict.
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The body of the organ is made up of braided strands of collagen (intrafusal fasciculi) that are less compact than elsewhere in the tendon and are encapsulated. The capsule is connected in series with a group of muscle fibers () at one end, and merge into the tendon proper at the other. Each capsule is about long, has a diameter of about , and is perforated by one or more afferent type Ib sensory nerve fibers (Aɑ fiber), which are large myelinated axons that can conduct nerve impulses very rapidly. Inside the capsule, the afferent fibers lose their medullary sheaths, branch, intertwine with the collagen fibers, and terminate as flattened leaf-like endings between the collagen strands (see figure).
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Vasodilation of the afferent arteriole, which results in increased glomerular filtration pressure and tubular fluid flow, occurs when MD cells detect a chloride concentration that is below a target value. A higher fluid flow rate in the TAL allows less time for dilution of the tubular fluid so that MD chloride concentration increases. Glomerular flow is decreased if the chloride concentration is above the target value. Constricting the smooth muscle cells in the afferent arteriole, results in a reduced concentration of chloride at the MD. TGF stabilizes the fluid and solute delivery into the distal portion of the loop of Henle and maintain the rate of filtration near its ideal value using these mechanisms.
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The occipital lymph nodes, one to three in number, are located on the back of the head close to the margin of the trapezius and resting on the insertion of the . Their afferent vessels drain the occipital region of the scalp, while their efferents pass to the superior deep cervical glands.
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The subthalamus develops efferent (output) connections to the striatum (caudate nucleus and putamen) in the telencephalon, to the dorsal thalamus (medial and lateral nuclear groups) in the diencephalon, and to the red nucleus and substantia nigra in the mesencephalon. It receives afferent (input) connections from the substantia nigra and striatum.
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The optic nerve (CNII) attaches to the diencephalon. The optic nerve is a sensory (afferent) nerve responsible for vision; it runs from the eye through the optic canal in the skull and attaches to the diencephalon. The retina itself is derived from the optic cup, a part of the embryonic diencephalon.
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Striatal arborisations, emit perpendicular branches participating in flat bands parallel to the lateral border, which increases the density of synapses in this direction. This is true for not only for the striatal afferent but also for the subthalamic (see below). The synaptology of the set is uncommon and characteristic.Fox et al.
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Pain, visual loss, relapse, and steroid response are typical of CRION. Ocular pain is typical, although there are some cases with no reported pain. Bilateral severe visual loss (simultaneous or sequential) usually occurs, but there are reports of unilateral visual loss. Patients can have an associated relative afferent pupillary defect.
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Vasopressin antagonists :Tolvaptan showed to have no benefit. It is also a very costly drug. Adenosine antagonists :Adenosine is responsible for constriction of afferent arteriole and reduction in GFR. It was found that an adenosine A1-receptor antagonist called KW-3902 was able to improve kidney function in CRS patients.
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The motor neuron is present in the grey matter of the spinal cord and medulla oblongata, and forms an electrochemical pathway to the effector organ or muscle. Besides motor nerves, there are efferent sensory nerves that often serve to adjust the sensitivity of the signal relayed by the afferent sensory nerve.
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The entorhinal cortex (EC) is composed of six layers. Superficial layer I consists largely of afferent fibers onto the apical dendrites of the cells in layers II-VI. Caudal levels project strongly to rostral levels. Within each EC area, deeper layers innervate superficial layers, with superficial layers innervating adjacent superficial layers.
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In the piriform cortex, layer I consists mostly of afferent inputs to apical dendrites of deeper cells. Layer I is subdivided into layers Ia and Ib each having its own afferents. Layer II is densely packed with pyramidal and semilunar cells. Layer III contains mostly pyramidal cells in its superficial part.
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Garnett, R. & Stephens, JA. The reflex responses of single motor units in human first dorsal interosseous muscle following cutaneous afferent stimulation. J. Physiol. Land. 303: 35 l-364, 1980.Kanda, K., Burke, R. E., & Walmsley, B. Differential control of fast and slow twitch motor units in the decerebrate cat. Exp.
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Adpressed: with overlapping whorls or with a suture tightly pressed to the previous whorl (preferred to the term appressed) Afferent. To bring in; when relating to a vessel or duct, indicating that it brings in its contents. Amoeboid. Shaped like an amoeba, a small animalcule. Amorphous. Without distinct form. Amphibious.
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The proximal end of the specific axon leads into the spinal cord on the dorsal half. This then moves towards the brain. These axons that are leading the signal towards the spinal cord to the brain are classified as primary afferents. This makes sense as afferent is defined conducting toward something.
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The IP3 causes the release of intracellular calcium, which spreads to neighboring cells via gap junctions creating a "TGF calcium wave". This causes afferent arteriolar vasoconstriction, decreasing the glomerular filtrate rate. #The Gi and increased intracellular calcium, cause a decrease in cAMP which inhibits Renin release from the juxtaglomerular cells.
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Glomerular mesangial cells structurally support the tufts. Blood enters the capillaries of the glomerulus by a single arteriole called an afferent arteriole and leaves by an efferent arteriole. The capillaries consist of a tube lined by endothelial cells with a central lumen. The gaps between these endothelial cells are called fenestrae.
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The trophosome of vestimentiferans is a complex, multi-lobed body with a vascular blood system that covers the entire trunk region. Each lobule consists of a tissue of bacteriocytes enclosed by an aposymbiotic coelothel. It is traversed by an axial efferent blood vessel, and is supplied with ramifying peripheral afferent blood vessels.
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The ventral reticular nucleus is a continuation of the parvocellular nucleus in the brainstem. The ventral reticular nucleus has been shown to receive afferent projections from the dentate gyrus in rabbits.Tang, ZW et al. The fiber projections from the dentate nucleus to the reticular formation of the brain stem in the rabbit.
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There is a yellow circle around the blue rhinophores. The gills are colorless with a black line alone the afferent vessel and a yellow with black one along the efferent vessel. The tail is white with orange yellow lines and black spots, edged with blue. The sides of the foot bear yellow stripes.
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A branch of the Group III afferent synapse an excitatory interneuron, which extends its axon across the midline into the contralateral spinal cord. At that location, the interneuron excites the alpha motor neurons that innervate the extensor muscles of the opposite leg. This allows for balance and body posture to be maintained.
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Dissolved chemicals interact with these receptor cells; different tastes bind to specific receptors. Salt and sour receptors are chemically gated ion channels, which depolarize the cell. Sweet, bitter, and umami receptors are called gustducins, specialized G protein coupled receptors. Both divisions of receptor cells release neurotransmitters to afferent fibers causing action potential firing.
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The splanchnic nerves are paired visceral nerves (nerves that contribute to the innervation of the internal organs), carrying fibers of the autonomic nervous system (visceral efferent fibers) as well as sensory fibers from the organs (visceral afferent fibers). All carry sympathetic fibers except for the pelvic splanchnic nerves, which carry parasympathetic fibers.
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Haptic memory represents SM for the tactile sense of touch. Sensory receptors all over the body detect sensations such as pressure, itching, and pain. Information from receptors travel through afferent neurons in the spinal cord to the postcentral gyrus of the parietal lobe in the brain. This pathway comprises the somatosensory system.
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The nerve fibers travel up to the spinal cord where they cross the midline, go to the left side, and synapse on an interneuron. When the afferent nerve fibers synapse on the interneuron, they can either inhibit or excite an alpha motor neuron on the muscles on side contralateral to the stimulus.
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Efference copy relates to Coriolis effect in a manner that allows for learning and correction of errors experienced from self-generated Coriolis forces. During trunk rotational movements there is a learned CNS anticipation of Coriolis effects, mediated by generation of an appropriate efference copy that can be compared to re-afferent information.
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Coughing is viewed as a public health issue. A cough is a protective reflex in healthy individuals which is influenced by psychological factors. The cough reflex is initiated by stimulation of two different classes of afferent nerves, namely the myelinated rapidly adapting receptors, and nonmyelinated C-fibers with endings in the lung.
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Anterior cingulate cortex can further be divided in the perigenual anterior cingulate cortex (near the genu) and midcingulate cortex. The anterior cingulate cortex receives primarily its afferent axons from the intralaminar and midline thalamic nuclei (see thalamus). The nucleus anterior receives mamillo-thalamic afferences. The mamillary neurons receive axons from the subiculum.
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Taste can be tested on the anterior two-thirds of the tongue. This can be tested with a swab dipped in a flavoured solution, or with electronic stimulation (similar to putting your tongue on a battery). Corneal reflex. The afferent arc is mediated by the general sensory afferents of the trigeminal nerve.
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As intrafusal muscle fibers, nuclear chain fibers are innervated by both sensory afferents and motor efferents. The afferent innervation is via type Ia sensory fibers and type II sensory fibers. These project to the nucleus proprius in the dorsal horn of the spinal cord. Efferent innervation is via static γ motor neurons.
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Mushroom Bodies of the Fruit Fly These regions are often modular and serve a particular role within the general systemic pathways of the nervous system. For example, the hippocampus is critical for forming memories in connection with many other cerebral regions. The peripheral nervous system also contains afferent or efferent nerves, which are bundles of fibers that originate from the brain and spinal cord, or from sensory or motor sorts of peripheral ganglia, and branch repeatedly to innervate every part of the body. Nerves are made primarily of the axons or dendrites of neurons (axons in case of efferent motor fibres, and dendrites in case of afferent sensory fibres of the nerves), along with a variety of membranes that wrap around and segregate them into nerve fascicles.
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Nevertheless, Broca's area in the left hemisphere and its homologue in the right hemisphere are designations usually used to refer to the triangular part of inferior frontal gyrus (PTr) and the opercular part of inferior frontal gyrus (POp). The PTr and POp are defined by structural landmarks that only probabilistically divide the inferior frontal gyrus into anterior and posterior cytoarchitectonic areas of 45 and 44, respectively, by Brodmann's classification scheme. Area 45 receives more afferent connections from the prefrontal cortex, the superior temporal gyrus, and the superior temporal sulcus, compared to area 44, which tends to receive more afferent connections from motor, somatosensory, and inferior parietal regions. The differences between area 45 and 44 in cytoarchitecture and in connectivity suggest that these areas might perform different functions.
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The sense of taste is based on the detection of chemicals by specialized taste cells in the mouth. The mouth, throat, larynx, and esophagus all have taste buds, which are replaced every ten days. Each taste bud contains receptor cells. Afferent nerves make contact with the receptor cells at the base of the taste bud.
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Simplified schema of basic nervous system function. Signals are picked up by sensory receptors and sent to the spinal cord and brain via the afferent leg of the peripheral nervous system, whereupon processing occurs that results in signals sent back to the spinal cord and then out to motor neurons via the efferent leg.
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These circuits transform sensory information into an action or movement. The parieto-frontal circuits are the basic compositions of the main elements of the cortical motor system. These circuits depend on the motor area to receive afferent information from the parietal areas. The input in one area is predominant, containing full amounts of information.
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The feedback from the carotid body is sent to the cardiorespiratory centers in the medulla oblongata via the afferent branches of the glossopharyngeal nerve. The efferent fibres of the aortic body chemoreceptors are relayed by the vagus nerve. These centers, in turn, regulate breathing and blood pressure, with hypoxia causing an increase in ventilation.
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J. Physiol. (London) 540: 189-207, 2002. Experiments with Yan Lu and Jihong Zheng were aimed at a better understanding of connections between spinal neurons and how afferent input from the periphery is modulated by these connections.Lu Y and Perl ER. A specific inhibitory pathway between substantia gelatinosa neurons receiving direct C-fiber input.
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In the nervous system there is a "closed loop" system of sensation, decision, and reactions. This process is carried out through the activity of sensory neurons, interneurons, and motor neurons. A touch or painful stimulus, for example, creates a sensation in the brain only after information about the stimulus travels there via afferent nerve pathways.
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Neuropathic itch can originate at any point along the afferent pathway as a result of damage of the nervous system. They could include diseases or disorders in the central nervous system or peripheral nervous system. Examples of neuropathic itch in origin are notalgia paresthetica, brachioradial pruritus, brain tumors, multiple sclerosis, peripheral neuropathy, and nerve irritation.
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Primate research since the 1980s through to the present has established that cortical regions relation to higher-order cognition primarily send afferent neurons to the rostal-most portion of the putamen, while the remainder of this structure in primates primarily serves sensori-motor functions and is densely interconnected with primary and supplementary motor regions.
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Met-enkephalin is found mainly in the adrenal medulla and throughout the central nervous system (CNS), including in the striatum, cerebral cortex, olfactory tubercle, hippocampus, septum, thalamus, and periaqueductal gray, as well as the dorsal horn of the spinal cord. It is also present in the periphery, notably in some primary afferent fibers that innervate the pelvic viscera.
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A rapid response system (RRS) is a tool implemented in hospitals designed to identify and respond to patients with early signs of clinical deterioration on non-intensive care units with the goal of preventing respiratory or cardiac arrest. A RRS consists of two clinical components (afferent and efferent) and two organizational components (process improvement and administrative).
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They do this by transducing mechanical movements or signals into neural activity. When stimulated, the stereocilia on the IHCs move, causing a flow of electric current to pass through the hair cells. This electric current creates action potentials within the connected afferent neurons. OHCs are different in that they actually contribute to the active mechanism of the cochlea.
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The neurons in the superior ganglion of the vagus nerve are pseudounipolar and provide sensory innervation (general somatic afferent) through either the auricular or meningeal branch. The axons of these neurons synapse in the spinal trigeminal nucleus of the brainstem. Peripherally, the neurons found in the superior ganglion form two branches, the auricular and meningeal branch.
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The same axon may reach other parts of the same dendritic arborisation (forming "random cascades")Percheron, 1991 With this pattern, it is more than likely that 1 or even 5 striatal axons are not able to influence (to inhibit) the activity of one pallidal neuron. Certain spatio-temporal conditions would be necessary for this, implying more afferent axons.
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The internal pudendal veins give drainage. Afferent lymph vessels carry lymph away from the vulva to the inguinal lymph nodes. The nerves that supply the vulva are the pudendal nerve, perineal nerve, ilioinguinal nerve and their branches. Blood and nerve supply to the vulva contribute to the stages of sexual arousal that are helpful in the reproduction process.
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Experiments with Takao Kumazawa in the late 1960s into the mid-1970s confirmed in monkey observations about unmyelinated primary afferent fibers and their central projections that had earlier been seen in cats.Kumazawa T and Perl ER. Primary cutaneous receptors with unmyelinated (C) fibres and their projection to the substantia gelatinosa. J. Physiol. (Paris) 73: 287-304, 1977.
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Réthelyi M, Light AR, and Perl ER. Synaptic complexes formed by functionally defined primary afferent units with fine myelinated fibers. J. Comp. Neurol. 207: 381-393, 1982. In a methodological tour de force, Perl worked with Yasuo Sugiura and Chong Lee in the mid-1980s to physiologically characterize and label (with Phaseolus vulgaris leucoagglutinin) unmyelinated C-fibers.
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Primary cell bodies are in the mesencephalic nucleus of the trigeminal nerve. These fibers transmit information to secondary afferent cell bodies in the oralis and interpolaris portions of the spinal trigeminal nucleus plus the principal nucleus. Axons from the spinal nucleus (and a smaller number from the principal nucleus) then form the trigeminocerebellar tract and ascend to the cerebellum.
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According to this research group, it takes place through a series of steps. When a receiver is interacting with a sender, he perceives the emotional expressions of the sender. The receiver automatically mimics those emotional expressions. Through the process of afferent feedback, these new expressions are translated into feeling the emotions the sender feels, thus leading to emotional convergence.
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The cerebellar glomeruli are the first "processing station" for afferent nerve fibers entering the cerebellum. Input comes from the mossy fibers, which terminate there and synapse with the Golgi and granule cell fibers. The Golgi cells regulate the glomeruli with inhibitory signals, while information is passed on to the granule and Golgi cells from the mossy fiber.
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A cerebellar glomerulus is about 2.5 um in diameter, and is wrapped by glial sheathing. Glomeruli are centered on the large axonal terminals of glutamatergic afferent mossy fibers. Each terminal comes into contact with dendrites from 50–60 different granule cells. The granule cells themselves each have a single or multiple dendrites, and each participates in a different glomerulus.
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In sensory transduction, the afferent nerves transmit through a series of synapses in the central nervous system, first in the spinal cord or trigeminal nucleus, depending on the dermatomic area concerned. One pathway then proceeds to the ventrobasal portion of the thalamus, and then on to the somatosensory cortex.Mada S. S. (2000): Human Biology. McGraw–Hill, New York, .
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The afferent neurons are either A fibers or C fibers. A fibers are myelinated allowing for faster signal conduction. Among these there are A beta fibers which are faster and carry information about non-painful touch and A delta fibers which are slower and thinner than the A beta fibers. The C fibers are not myelinated and therefore slower.
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The sensory feedback originates from muscles, joints, tendons and skin afferents as well as from special senses and dynamically adapts the locomotor pattern of spinal cord to the requirements of the environment. These afferent sensory receptors perceive deformation of tissue, the amount of pressure (stretch or simply, placement), direction of movement, speed and velocity at which movement is occurring.
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Lifecycle of Wuchereria bancrofti W. bancrofti carries out its lifecycle in two hosts. Humans serve as the definitive host and mosquitos as the intermediate host. The adult parasites reside in the lymphatics of the human host. They are found mostly in the afferent lymphatic channels of the lymph glands in the lower part of the body.
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The steadily increasing pressure first forces the toes against the spikes, mangling their flesh and crushing their bones. Under continued inexorable pressure, the bones of the instep eventually give way until the arch of the foot is shattered. The heel bone is sufficiently powerful to withstand the torture, although the heel is not generously provided with afferent pain nociceptors.
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Mammalian tendon organ showing typical position in a muscle (left), neuronal connections in spinal cord (middle) and expanded schematic (right). The tendon organ is a stretch receptor that signals the force developed by the muscle. The sensory endings of the Ib afferent are entwined amongst the musculotendinous strands of 10-20 extrafusal muscle fibers. See an animated version.
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Burke RE, Walmsley B, Hodgson JA. HRP anatomy of group Ia afferent contacts on alpha motoneurones. Brain Res. 1979 Jan 12;160(2):347-52 The topic is probably still regarded as controversial. Under some circumstances, the normal order of motor unit recruitment may be altered, such that small motor units cease to fire and larger ones may be recruited.
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The GnRH neurons are regulated by many different afferent neurons, using several different transmitters (including norepinephrine, GABA, glutamate). For instance, dopamine appears to stimulate LH release (through GnRH) in estrogen-progesterone-primed females; dopamine may inhibit LH release in ovariectomized females. Kisspeptin appears to be an important regulator of GnRH release. GnRH release can also be regulated by estrogen.
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The CA3 of the hippocampus plays an especially important role in the encoding and retrieval of spatial memories. The CA3 is innervated by two afferent paths known as the perforant path (PPCA3) and the dentate gyrus (DG)-mediated mossy fibers (MFs). The first path is regarded as the retrieval index path while the second is concerned with encoding.
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For example, Naive T cells express the CCR7 receptor for the chemokine CCL21. and B cells exhibit CXCR5 receptors for chemokine CXCL13. The lymph from the peripheral tissues contains soluble antigens and arrives at the lymph node via afferent lymphatic vessels. An adaptive immune response takes place in response to the presence of the antigen in the lymph node.
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Location of structures connected to the gustatory nucleusBasic neuroanatomy of the gustatory system.Different taste receptors in the tongue and their connections to afferent neurons. The gustatory nucleus is the rostral part of the solitary nucleus located in the medulla. The gustatory nucleus is associated with the sense of taste and has two sections, the rostral and lateral regions.
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Convergence facilitation was conceived in 1893 by J MacKenzie based on the ideas of Sturge and Ross. He believed that the internal organs were insensitive to stimuli. Furthermore, he believed that non-nociceptive afferent inputs to the spinal cord created what he termed "an irritable focus". This focus caused some stimuli to be perceived as referred pain.
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From a stimulus-response perspective, the perception of physical pain starts with the nociceptors, a type of physiological receptor that transmits neural signals to the brain when activated. These receptors are commonly found in the skin, membranes, deep fascias, mucosa, connective tissues of visceral organs, ligaments and articular capsules, muscles, tendons, periosteum, and arterial vessels. Once stimuli are received, the various afferent action potentials are triggered and pass along various fibers and axons of these nociceptive nerve cells into the dorsal horn of the spinal cord through the dorsal roots. A neuroanatomical review of the pain pathway, "Afferent pain pathways" by Almeida, describes various specific nociceptive pathways of the spinal cord: spinothalamic tract, spinoreticular tract, spinomesencephalic tract, spinoparabrachial tract, spinohypothalamic tract, spinocervical tract, postsynaptic pathway of the spinal column.
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There are three major types of bladder dysfunction due to neural lesions: (1) the type due to interruption of the afferent nerves from the bladder; (2) the type due to interruption of both afferent and efferent nerves; and (3) the type due to interruption of facilitatory and inhibitory pathways descending from the brain. In all three types the bladder contracts, but the contractions are generally not sufficient to empty the viscus completely, and residual urine is left in the bladder. Paruresis, also known as shy bladder syndrome, is an example of a bladder interruption from the brain that often causes total interruption until the person has left a public area. As these people may have difficulty urinating in the presence of others and will consequently avoid using urinals directly adjacent to another person.
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The right side of the auricle stretches backward, and receives a similar trunk- vein from the skin of this side almost at the posterior extremity of the pericardium. On laying the dorsal wall of the auricle open, its cavity is found to be continuous with that of the great posterior elevated median ridge or trunk vein before alluded to, and on opening this trunk-vein the various lateral branches are observed debouching into it on either side. It is therefore evident that this trunk-vein, which lies entirely within the skin, is the great posterior afferent or branchio-cardiac vein, and that all the elevated branches coming to it from the cerata are also afferent vessels. This way are cerata used for breathing as a specialized breathing organ.
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The VPM contains synapses between second and third order neurons from the anterior (ventral) trigeminothalamic tract and posterior (dorsal) trigeminothalamic tract. These neurons convey sensory information from the face and oral cavity. Third order neurons in the trigeminothalamic systems project to the postcentral gyrus. The VPM also receives taste afferent information from the solitary tract and projects to the cortical gustatory area.
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One method that the brain uses to evaluate the contents of the gut is through vagal nerve fibers that carry signals between the brain and the gastrointestinal tract (GI tract). Stretch receptors work to inhibit appetite upon distention of the GI tract by sending signals along the vagus nerve afferent pathway and inhibiting the hunger center.Marieb, E., & Marieb, E. (2010). Human anatomy & physiology.
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The early tetrapod Acanthostega had at least three and probably four pairs of gill bars, each containing deep grooves in the place where one would expect to find the afferent branchial artery. This strongly suggests that functional gills were present. Some aquatic temnospondyls retained internal gills at least into the early Jurassic. Evidence of clear fish-like internal gills is present in Archegosaurus.
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At the center of each Grandry corpuscle is the terminal end of an afferent nerve fiber. A single nerve fiber enters each corpuscle and becomes unmyelinated a short distance into the capsule. This fiber can be one of several branches from a single nerve axon that innervates multiple Grandry corpuscles. The unmyelinated nerve then flattens into a wide disc containing many mitochondria.
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The central auditory system converges inputs from both ears (inputs contain no explicit spatial information) onto single neurons within the brainstem. This system contains many subcortical sites that have integrative functions. The auditory nuclei collect, integrate, and analyze afferent supply, the outcome is a representation of auditory space. The subcortical auditory nuclei are responsible for extraction and analysis of dimensions of sounds.
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It has been suggested that myofibroblasts also reside in the lamina propria of several organs. These cells have characteristics of both smooth muscle and fibroblasts. The lamina propria may also be rich in vascular networks, lymphatic vessels, elastic fibers, and smooth muscle fascicles from the muscularis mucosae. Afferent and efferent nerve endings can be found in the lamina propria as well.
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The swinging-flashlight test is the most useful clinical test available to a general physician for the assessment of optic nerve anomalies. This test detects the afferent pupil defect, also referred to as the Marcus Gunn pupil. It is conducted in a semidarkened room. In a normal reaction to the swinging-flashlight test, both pupils constrict when one is exposed to light.
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Intrafusal muscle fibers are skeletal muscle fibers that serve as specialized sensory organs (proprioceptors) that detect the amount and rate of change in length of a muscle.Casagrand, Janet (2008) Action and Movement: Spinal Control of Motor Units and Spinal Reflexes. University of Colorado, Boulder. They constitute the muscle spindle and are innervated by both sensory (afferent) and motor (efferent) fibers.
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Thus, it results in creating the behavioral reflex. At the same time, the other branch of the Ia afferent synapses on to the Ia inhibitory interneuron, which in turn synapses the alpha motor neuron of the antagonist muscle. Since Ia interneuron is inhibitory, it prevents the opposing alpha motor neuron from firing. Thus, it prevents the antagonist muscle from contracting.
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C fibers have slow conduction velocities of less than 1.3 m/s because they do not have a myelin sheath at all. C fibers account for 60-70% of primary afferent neurons that innervate the skin. C fibers are activated by both mechanical and thermal stimuli, and also respond to algesic chemicals, such as capsaicin. Some C fibers respond only to mechanical stimuli.
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It receives afferent input, specifically electrosensory, mechanical, and auditory stimuli. In frogs, researchers have studied how neurons in the torus semicircularis prefer certain characteristics of sound differentially. Single neurons fire selectively based on the auditory parameters of a stimulus. Functionally, this can allow members of a species to distinguish whether a call is of the same (conspecific) or a different species.
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Warrell D. A., Cox T. M., Firth J. D. (2010): The Oxford Textbook of Medicine (5th ed.). Oxford University Press which carries impulses by way of the afferent nerve fibers of sensory neurons. In the nervous system there is a "closed loop" system of sensation, decision, and reactions. This process is carried out through the activity of sensory neurons, interneurons, and motor neurons.
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Four TRPVs (TRPV1, TRPV2, TRPV3, and TRPV4) are expressed in afferent nociceptors, pain sensing neurons, where they act as transducers of thermal and chemical stimuli. Hence antagonists or blockers of these channels may find application for the prevention and treatment of pain. A number of TRPV1 selective blockers are currently in clinical trials for the treatment of various types of pain.
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When the muscle generates force, the sensory terminals are compressed. This stretching deforms the terminals of the Ib afferent axon, opening stretch-sensitive cation channels. As a result, the Ib axon is depolarized and fires nerve impulses that are propagated to the spinal cord. The action potential frequency signals the force being developed by 10-20 extrafusal muscle fibers in the muscle.
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Emerging from the anterolateral sulci are the CN XII (hypoglossal nerve) rootlets. Lateral to these rootlets and the anterolateral sulci are the olives. The olives are swellings in the medulla containing underlying inferior nucleary nuclei (containing various nuclei and afferent fibers). Lateral (and dorsal) to the olives are the rootlets for CN IX (glossopharyngeal), CN X (vagus) and CN XI (accessory nerve).
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The Biology of the Deep Ocean. New York: Oxford, 2002. The cupula, and the stereocilia which are the "hairs" of hair cells, are moved by a certain amount depending on the movement of the surrounding water. Afferent nerve fibers are excited or inhibited depending on whether the hair cells they arise from are deflected in the preferred or opposite direction.
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Nerves that transmit signals from the brain are called motor or efferent nerves, while those nerves that transmit information from the body to the CNS are called sensory or afferent. Spinal nerves serve both functions and are called mixed nerves. The PNS is divided into three separate subsystems, the somatic, autonomic, and enteric nervous systems. Somatic nerves mediate voluntary movement.
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The cell bodies for the facial nerve are grouped in anatomical areas called nuclei or ganglia. The cell bodies for the afferent nerves are found in the geniculate ganglion for taste sensation. The cell bodies for muscular efferent nerves are found in the facial motor nucleus whereas the cell bodies for the parasympathetic efferent nerves are found in the superior salivatory nucleus.
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Sherrington pointed out that reflexes must be goal- directive and purposive. Furthermore, he established the nature of postural reflexes and their dependence on the anti-gravity stretch reflex and traced the afferent stimulus to the proprioceptive end organs, which he had previously shown to be sensory in nature ("proprioceptive" was another term he had coined). The work was dedicated to Ferrier.
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After stroke or spinal cord injury in humans, spastic hypertonia (spastic paralysis) often develops, whereby the stretch reflex in flexor muscles of the arms and extensor muscles of the legs is overly sensitive. This results in abnormal postures, stiffness and contractures. Hypertonia may be the result of over-sensitivity of alpha motoneurons and interneurons to the Ia and II afferent signals.
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A neuron's response to trauma can often be determined by the severity of the injury, classified by Seddon's classification. In Seddon's Classification, nerve injury is described as either neurapraxia, axonotmesis, or neurotmesis. Following trauma to the nerve, a short onset of afferent impulses, termed "injury discharge", occurs. While lasting only minutes, this occurrence has been linked to the onset of neuropathic pain.
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The location of the receptor that is stimulated gives the brain information about the location of the stimulus (for example, stimulating a mechanoreceptor in a finger will send information to the brain about that finger). The duration of the stimulus (how long it lasts) is conveyed by firing patterns of receptors. These impulses are transmitted to the brain through afferent neurons.
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Retrieved December 05, 2017, from The dorsal funiculus is located between the dorsal horn and the medial line in the spinal cord. There are three types of neurons in the pathway: first-, second-, and third-order neurons. The first-order neuron is the afferent neuron. It enters the spinal cord through the dorsal root ganglia and branches in the spinal cord.
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Diagram of the circulation related to a single glomerulus, associated tubule, and collecting system. The glomerulus receives its blood supply from an afferent arteriole of the renal arterial circulation. Unlike most capillary beds, the glomerular capillaries exit into efferent arterioles rather than venules. The resistance of the efferent arterioles causes sufficient hydrostatic pressure within the glomerulus to provide the force for ultrafiltration.
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The oxygenated blood from the heart leads to the aorta, to sinuses where it oxygenates tissues. Deoxygenated blood goes to efferent branchial vessels in cerata. These efferent vessels can be seen in a transverse section of the cerata as widish canal to pass up the opposite margin. From efferent vessels the blood goes into afferent vessel, where is gets an oxygen.
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Each regular office floor is designed to host open space offices with afferent toilets and connections ready for installing the kitchenettes, accommodating up to 60 working stations, benefiting from a specially designed meeting area. On June 6, 2012, SkyTower has reached the 36th floor and became the tallest building in Romania. The topping out ceremony was held on June 28, 2012.
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In the kidney, the macula densa is an area of closely packed specialized cells lining the wall of the distal tubule, at the point where the thick ascending limb of the Loop of Henle meets the distal convoluted tubule. The macula densa is the thickening where the distal tubule touches the glomerulus. The cells of the macula densa are sensitive to the concentration of sodium chloride in the distal convoluted tubule. A decrease in sodium chloride concentration initiates a signal from the macula densa that has two effects: (1) it decreases resistance to blood flow in the afferent arterioles, which raises glomerular hydrostatic pressure and helps return the glomerular filtration rate (GFR) toward normal, and (2) it increases renin release from the juxtaglomerular cells of the afferent and efferent arterioles, which are the major storage sites for renin.
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This inhibition is accomplished by the actions of an inhibitory interneuron in the spinal cord. The afferent of the muscle spindle bifurcates in the spinal cord. One branch innervates the alpha motor neuron that causes the homonymous muscle to contract, producing the reflex. The other branch innervates the inhibitory interneuron, which in turn innervates the alpha motor neuron that synapses onto the opposing muscle.
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Targeted sensory reinnervation was discovered by accident. While receiving an alcohol rub on his chest after the surgery, the patient described a sensation of being touched on the pinky. The explanation for this phenomenon is that, since his subcutaneous fat was removed during surgery, his chest skin was denervated. Thus, the afferent nerve fibers regenerated through the pectoral muscle, reinnervating the skin over the muscle.
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When postsynaptic action potential firing occurs prior to presynaptic afferent firing, both presynaptic endocannabinoid (CB1) receptors and NMDA receptors are stimulated at the same time. Postsynaptic spiking alleviates the Mg2+ block on NMDA receptors. The postsynaptic depolarization will subside by the time an EPSP occurs, enabling Mg2+ to return to its inhibitory binding site. Thus, the influx of Ca2+ in the postsynaptic cell is reduced.
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Baroreflex activation is distinct from vagal stimulation. Electrical stimulation of the external surfaces of the carotid sinus activates baroreceptors believed to be in the adventitia of the artery. This stimulates an afferent limb which activates central nervous system pathways that in turn exert two different but synergistic autonomic effects on the body. First, global sympathetic outflow is reduced and, second, vagal outflow is increased.
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Stump blow-out, or duodenal blow-out, is the leakage of the blind end of the duodenum. It occurs as a complication of Billroth II gastrectomy, usually on the fourth or fifth day after surgery. It is due to improper closure of duodenal stump, especially when the duodenum is inflamed and oedematous. It can also occur because of afferent loop block, local pancreatitis and distal obstruction.
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The optic tract syndrome is characterized by a contralateral, incongruous homonymous hemianopia, contralateral relative afferent pupillary defect (RAPD), and optic atrophy due to retrograde axonal degeneration. Causes of optic tract lesions are also classified into intrinsic and extrinsic forms. Intrinsic lesions include demyelinating diseases and infarction. Such lesions produce optic tract syndrome type II. Extrinsic or compressive lesions are caused by pituitary craniopharyngioma, tumours of optic thalamus.
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H-reflex study uses stimulation of a nerve and recording the reflex electrical discharge from a muscle in the limb. This also evaluates conduction between the limb and the spinal cord, but in this case, the afferent impulses (those going toward the spinal cord) are in sensory nerves while the efferent impulses (those coming from the spinal cord) are in motor nerves. This process cannot be changed.
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In many cases, the infected animal is exceptionally aggressive, may attack without provocation, and exhibits otherwise uncharacteristic behavior. This is an example of a viral pathogen modifying the behavior of its host to facilitate its transmission to other hosts. After a typical human infection by bite, the virus enters the peripheral nervous system. It then travels along the afferent nerves toward the central nervous system.
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The dorsal root of spinal nerve (or posterior root of spinal nerve) is one of two "roots" which emerge from the spinal cord. It emerges directly from the spinal cord, and travels to the dorsal root ganglion. Nerve fibres with the ventral root then combine to form a spinal nerve. The dorsal root transmits sensory information, forming the afferent sensory root of a spinal nerve.
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Recording of single afferent impulses from C-fibers is particularly demanding as they have a diameter of only one micrometer. A method to increase the yield is the marking technique which is based on a unique property of many kinds of C-fibres, i.e. a decrease of conduction velocity in the wake of preceding impulses. By combining repetitive electrical stimulation and physical stimulation, e.g.
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Nociceptors were discovered by Charles Scott Sherrington in 1906. In earlier centuries, scientists believed that animals were like mechanical devices that transformed the energy of sensory stimuli into motor responses. Sherrington used many different experiments to demonstrate that different types of stimulation to an afferent nerve fiber's receptive field led to different responses. Some intense stimuli trigger reflex withdrawal, certain autonomic responses, and pain.
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This layer is also known as the substantia gelatinosa of Rolando and has the highest density of neurons. These neurons mediate the activity of nociceptive and temperature afferent fibers. It is almost entirely made up of interneurons which can be further divided by their morphology. The four main morphological classes, based on the shape of their dendritic structure, are islet, central, vertical, and radial cells.
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The first order afferent neuron carries sensory information to the second order neuron in the dorsal horn. The axon of the second order neuron, if it is a projection neuron and not an interneuron, then goes to the third order neuron in the thalamus. The thalamus is known as the "gateway to the cortex". The third order neuron then goes to the cerebral cortex.
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Papillitis may have the same appearance as papilledema. However, papillitis may be unilateral, whereas papilledema is almost always bilateral. Papillitis can be differentiated from papilledema by an afferent pupillary defect (Marcus Gunn pupil), by its greater effect in decreasing visual acuity and color vision, and by the presence of a central scotoma. Papilledema that is not yet chronic will not have as dramatic an effect on vision.
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Visual processes constitute an important part of higher cortical functioning. The encoding and interpretation of retinal stimulation occur at the neurological level upon reception of afferent input from the eyes. Reading, for example, requires the possession of both adequate vision and the neurological ability to process what is seen. In the past, many researchers have associated anomalies in the visual system as the main cause of dyslexia.
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In some applications, the nerves are stimulated to generate localized muscle activity, i.e., the stimulation is aimed at generating direct muscle contraction. In other applications, stimulation is used to activate simple or complex reflexes. In other words, the afferent nerves are stimulated to evoke a reflex, which is typically expressed as a coordinated contraction of one or more muscles in response to the sensory nerve stimulation.
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Histologically, the glomeruli show thickened and sometimes split capillary walls due largely to endothelial swelling. Large deposits of fibrin-related materials in the capillary lumens, subendothelially, and in the mesangium are also found along with mesangiolysis. Interlobular and afferent arterioles show fibrinoid necrosis and intimal hyperplasia and are often occluded by thrombi. STEC-HUS most often affects infants and young children, but also occurs in adults.
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The posterior cingulate cortex receives a great part of its afferent axons from the superficial nucleus (or nucleus superior- falsely LD-) of the thalamus (see thalamus), which itself receives axons from the subiculum. To some extent it thus duplicates Papez' circuit. It receives also direct afferents from the subiculum of the hippocampus. Posterior cingulate cortex hypometabolism (with 18F-FDG PET) has been defined in Alzheimer's disease.
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The efferent lymphatic vessel commences from the lymph sinuses of the medullary portion of the lymph nodes and leave the lymph nodes at the hilum, either to veins or greater nodes. It carries filtered lymph out of the node. Efferent lymphatic vessels are also found in the thymus and spleen. This is in contrast to afferent lymphatic vessels, which are found only in lymph nodes.
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The superficial parotid lymph nodes are a group of lymph nodes anterior to the ear. Their afferent vessels drain the root of the nose, the eyelids, the frontotemporal region, the external acoustic meatus and the tympanic cavity, possibly also the posterior parts of the palate and the floor of the nasal cavity. The efferents of these glands pass to the superior deep cervical glands.
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At the soma of the postganglionic sympathetic sudomotor neuron, the impulse branches and travels orthodromically, or away from the soma. Finally, as this impulse reaches other sweat glands, it causes an indirect axon-reflex sweat response. Sudomotor axon reflexes can be peripherally amplified in the transmission of the action potential magnitude by acetylcholine. Acetylcholine also activates sudomotor fibers and primary afferent nociceptors, triggering axon reflexes in both.
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Gamma motor neurons are also involved through their action on intrafusal muscle fibers. The intrafusal muscle fibers control the resting level of the Ia afferent pathway, which in turn creates a steady level of alpha neuron activity. Muscle tone can also be due to tonic discharge of gamma motor neurons. The activation to these neurons are mostly from the descending fibers of the facilitatory reticular formation.
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Each Edinger-Westphal nucleus gives rise to preganglionic parasympathetic fibers which exit with CN III and synapse with postganglionic parasympathetic neurons in the ciliary ganglion. Postganglionic nerve fibers leave the ciliary ganglion to innervate the ciliary sphincter. Each afferent limb has two efferent limbs, one ipsilateral and one contralateral. The ipsilateral efferent limb transmits nerve signals for direct light reflex of the ipsilateral pupil.
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Prorenin () is a protein that constitutes a precursor for renin, the hormone that activates the renin–angiotensin system, which serves to raise blood pressure. Prorenin is converted into renin by the juxtaglomerular cells, which are specialised smooth muscle cells present mainly in the afferent, but also the efferent, arterioles of the glomerular capillary bed. Prorenin is a relatively large molecule, weighing approximately 46 KDa.
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Diabetes mellitus is a disorder in which the body cannot break down glucose either because insulin is not produced or the body does not produce enough insulin. This causes glucose to accumulate in the blood. High concentrations of glucose in the blood can injure nerve fibers, resulting in diabetic neuropathy. In most cases, the nerve damage occurs in afferent neurons in the foot and lower limbs.
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The glomerulus receives its blood supply from an afferent arteriole of the renal arterial circulation. Unlike most capillary beds, the glomerular capillaries exit into efferent arterioles rather than venules. The resistance of the efferent arterioles causes sufficient hydrostatic pressure within the glomerulus to provide the force for ultrafiltration. The glomerulus and its surrounding Bowman's capsule constitute a renal corpuscle, the basic filtration unit of the kidney.
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There are small afferent vessels (1) in cerata with puckerd membranous fringe on the inner sides. The vessels are leading to great median trunk. Efferent vessels (2), gland (3) a "normal" tissue of cerata (4). The circulatory system and respiratory system is unique in this animal, because nearly the whole of these vessels are distinctly visible on the skin of the back, rising above the general surface.
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The stretch reflex is accomplished through several different structures. In the muscle, there are muscle spindles, whose extrafusal muscle fibers lie parallel to the muscle and sense changes in length and velocity. The afferent sensory neuron is the structure that carries the signal from the muscle to the spinal cord. It carries this action potential to the dorsal root ganglion of the spinal cord.
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However these afferent pathways may also transfer sources of information about the state and function of the body that could influence higher mental functions (cognition) and behaviour. By increasing interoceptive awareness one may develop methods of improving and regulating their own physiological performance and states of wellbeing. Buldeo, N (2015) Interoception: a measure of embodiment or attention? Int Body Psychother J. 2015;14(1):65–79.
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Modern scientists usually refer to the individual nuclei that compose the reticular formation. Moruzzi and Magoun first investigated the neural components regulating the brain's sleep-wake mechanisms in 1949. Physiologists had proposed that some structure deep within the brain controlled mental wakefulness and alertness. It had been thought that wakefulness depended only on the direct reception of afferent (sensory) stimuli at the cerebral cortex.
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An important aspect of intelligent behavior as studied in AI is goal-based problem solving, a framework in which the solution to a problem can be described by finding a sequence of actions that lead to a desirable goal. A goal-seeking system is supposed to be connected to its outside environment by sensory channels through which it receives information about the environment and motor channels through which it acts on the environment. (The term "afferent" is used to describe "inward" sensory flows, and "efferent" is used to describe "outward" motor commands.) In addition, the system has some means of storing in a memory information about the state of the environment (afferent information) and information about actions (efferent information). Ability to attain goals depends on building up associations, simple or complex, between particular changes in states and particular actions that will bring these changes about.
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Diagram showing the basic outline of nephron structure and function: diabetic nephropathy is associated with changes in the afferent and efferent arterioles, causing capillary hypertension; and damage to the glomerular capillaries of multiple causes, including mesangial matrix deposition The disease progression of diabetic nephropathy involves various clinical stages: hyperfiltration, microalbuminuria, macroalbuminuria, nephrotic proteinuria to progressive chronic kidney disease leading to end- stage renal disease (ESRD). The damage is exerted on all compartments of the kidney: the glomerulus, the renal tubules, the vasculature (afferent and efferent renal arterioles) and the interstitium. Renal fibrosis is the final common pathway of DN. This fibrosis is a product of multiple mechanisms including renal hemodynamic changes, glucose metabolism abnormalities associated with oxidative stress as well as inflammatory processes and an overactive renin-angiotensin-aldosterone system (RAAS). The pathophysiology of diabetic nephropathy is thought to involve an interaction between hemodynamic and metabolic factors.
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Whenever these afferent nerve endings are stimulated (for example, by dust, cold air or fumes) impulses travel to the brain-stem vagal center, then down the vagal efferent pathway to again reach the bronchial small airways. Acetylcholine is released from the efferent nerve endings. This acetylcholine results in the excessive formation of inositol 1,4,5-trisphosphate (IP3) in bronchial smooth muscle cells which leads to muscle shortening and this initiates bronchoconstriction.
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The spasticity occurs when the afferent pathways in the brain are compromised and the communication between the brain to the motor fibers is lost. When the inhibitory signals to deactivate the stretch reflex is lost the muscle remains in a constantly contracted state. With spastic hemiplegia, one upper extremity and one lower extremity is affected, so cervical, lumbar and sacral segments of the spinal column can be affected.
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In the gastrointestinal tract, mucosal mast cells are located in close proximity to sensory nerve fibres, which communicate bidirectionally. When these mast cells initially degranulate, they release mediators (e.g., histamine, tryptase, and serotonin) which activate, sensitize, and upregulate membrane expression of nociceptors (i.e., TRPV1) on visceral afferent neurons via their receptors (respectively, HRH1, HRH2, HRH3, PAR2, 5-HT3); in turn, neurogenic inflammation, visceral hypersensitivity, and intestinal dysmotility (i.e.
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The superior cerebellar peduncles (brachia conjunctiva) emerge from the cerebellum and ascend to form the lateral portion of the roof of the fourth ventricle, where they enter the brainstem below the inferior colliculi. They are bridged by the superior medullary velum. The superior cerebellar peduncles represent the main output route from the cerebellum, and as such, most of their fibers are efferent. A relatively small afferent contribution is present.
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Pathway of a Monosynaptic Reflex The reflex pathway (reflex arc) is a sequence of neurons connecting the sensory input (afferent neuron) to the motor output (efferent neuron), resulting in a behavioral response. The general pathway of a spinal reflex is one which involves neurons contained within the spinal cord. However, the brain may also provide additional (supraspinal) contributions, which can modulate the responsiveness of the reflex to the sensory input.
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Since plantar pressure sensation aids in balancing reactions in stepping movements, insoles with raised ridges along the edges can enhance stimulation of cutaneous mechanoreceptors that help to define the BOS. Most of the time, the ridges are made so that stimulation only occurs when the COM nears the BOS limit.Do MC., Bussel, B., Brenier Y. Influence of plantar cutaneous afferent on early compensatory reactions to forward fall. Exp Brain Res.
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The nonprimary motor cortex exerts its motor control at a higher neural level than the primary motor cortex by commanding the laterality of muscular motor response to the brain. This is carried out by afferent nerves from the nonprimary motor cortex synapsing at the primary motor cortex. Both divisions of the nonprimary motor cortex receive inputs from the thalamus and are responsible for sensory guidance and motor preparation.
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The lumbar splanchnic nerves are splanchnic nerves that arise from the lumbar part of the sympathetic trunk and travel to an adjacent plexus near the aorta. They originate from L1 and L2. These nerves contain preganglionic sympathetic and general visceral afferent fibers. The site of synapse is found in the inferior mesenteric ganglion and the postsynaptic fibers innervate the smooth muscle and glands of the pelvic viscera and hindgut.
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It is made of 31 segments from which branch one pair of sensory nerve roots and one pair of motor nerve roots. The nerve roots then merge into bilaterally symmetrical pairs of spinal nerves. The peripheral nervous system is made up of these spinal roots, nerves, and ganglia. The dorsal roots are afferent fascicles, receiving sensory information from the skin, muscles, and visceral organs to be relayed to the brain.
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The cough reflex has both sensory (afferent) mainly via the vagus nerve and motor (efferent) components. Pulmonary irritant receptors (cough receptors) in the epithelium of the respiratory tract are sensitive to both mechanical and chemical stimuli. The bronchi and trachea are so sensitive to light touch that slight amounts of foreign matter or other causes of irritation initiate the cough reflex. The larynx and carina are especially sensitive.
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The lumbar region L1 and L2 consist of neurons that innervate the adrenal gland, ureter, bladder, the lower extremities. The upper two lumbar ganglia (L1 and L2) of the sympathetic chain also give rise to the lumbar splanchnic nerves. Splanchnic nerves are paired visceral nerves carrying preganglionic sympathetic and general visceral afferent fibers. The lumbar splanchnic nerves travel through the lumbar sympathetic ganglion but do not synapse there.
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Re-afferent potentials (RAPs) are another form of ERP, and are used as a marker of sensory feedback and attention. Both MP and RAP have been demonstrated to be enhanced during compatible ACE conditions. These results indicate that language can have a facilitory effect on the excitability of neural sensorimotor systems. This has been referred to as semantic priming, indicating that language primes neural sensorimotor systems, altering excitability and movement.
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It measures changes in blood pressure and the composition of arterial blood flowing past it, including the partial pressures of oxygen and carbon dioxide. The chemoreceptors responsible for sensing changes in blood gases are called glomus cells. It gives feedback to the medulla oblongata, specifically to the dorsal respiratory group, via the afferent branches of the vagus nerve (X). The medulla, in turn, regulates breathing and blood pressure.
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Particularly, CT afferents respond vigorously to slow caressing movements, and, importantly, the size of the afferent response matches the sense of pleasure reported by the subject. fMRI studies of brain activity indicate that CT activate the insular cortex but not the primary or secondary somatosensory cortex consistent with the hypothesis that CT may play a role in emotional, behavioral, and hormonal responses to pleasant skin-to-skin contact between individuals.
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Measurement of a subject's center of pressure has been used as a method of quantifying postural stability. Investigators have theorized that if ankle injuries cause differentiation and functional instability, a subject's postural sway should be altered. Bracing has been known to provide cutaneous afferent feedback in maintaining postural control. The feedback follows the same neurological pathways in which the external ankle brace enhances the replication of the joint position.
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In the normal cell, some of these branches would form synapses, which is not the case in the neurons expressing the peptide. As a result, these cells have minimal dendritic arbors. This is because without AMPA receptors, the neuron can't cause neighboring neurons to fire action potentials, therefore disallowing their synapses to strengthen. As described previously, the pattern of dendritic branching depends on the initial contact of filopodia with afferent axons.
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In 1981, a graduate student and PETA member, Alex Pacheco, volunteered at a research center in Silver Spring, Maryland. At the time, Edward Taub was conducting research on monkeys for neuroplasticity purposes at that center. While Alex spent time at the research center, he noticed the inhumane treatment of the monkeys under the AWA and reported it to the police. He filed suit against Edward Taub, who was researching afferent ganglia.
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Afferent nociceptive fibers (those that send information to, rather than from the brain) travel back to the spinal cord where they form synapses in its dorsal horn. This nociceptive fiber (located in the periphery) is a first order neuron. The cells in the dorsal horn are divided into physiologically distinct layers called laminae. Different fiber types form synapses in different layers, and use either glutamate or substance P as the neurotransmitter.
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The basic MOC acoustic reflex. The auditory nerve responds to sound, sending a signal to the cochlear nucleus. Afferent nerve fibres cross the midline from the cochlear nucleus to the cell bodies of the MOCS (located near the MSOC), whose efferent fibres project back to the cochlea (red). In most mammals, the majority of the reflex is ipsilateral (shown as a thicker line), effectuated by the crossed MOCS.
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Efferent signals are the motor neuronal signals descending to the respiratory muscles. The most important respiratory muscle is the diaphragm. Other respiratory muscles include the external and internal intercostal muscles, the abdominal muscles and the accessory breathing muscles. As the brain receives its plentiful supply of afferent information relating to ventilation, it is able to compare it to the current level of respiration as determined by the efferent signals.
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Guyton & Hall Textbook Of Physiology, 11th Edition 2006, p. 324 As such, an increase in sodium chloride concentration would result in vasoconstriction of afferent arterioles, and reduced paracrine stimulation of juxtaglomerular cells. This demonstrates the macula densa feedback, where compensatory mechanisms act in order to return GFR to normal. The release of renin is an essential component of the renin–angiotensin–aldosterone system (RAAS), which regulates blood pressure and volume.
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Second, prostaglandin activates prostaglandin-sensitive specialized smooth muscle cells of the renal afferent arterioles, juxtaglomerular cells (JG cells), to release renin into the bloodstream. The JG cells can also release renin independently of the macula densa. There are stretch-sensitive baroreceptors lining the arterioles that will release renin if a fall in blood pressure (i.e. decreased stretch of arteriole due to less blood flow) in the arterioles is detected.
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Agraphia or impairment in producing written language can occur in many ways and many forms because writing involves many cognitive processes (language processing, spelling, visual perception, visuospatial orientation for graphic symbols, motor planning, and motor control of handwriting). Agraphia has two main subgroupings: central ("aphasic") agraphia and peripheral ("nonaphasic") agraphia. Central agraphias include lexical, phonological, deep, and semantic agraphia. Peripheral agraphias include allographic, apraxic, motor execution, hemianoptic and afferent agraphia.
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Each of these three categories have their own types of pathways and receptors. These pathways target the cerebellum in the brain. This section of the brain tracks what the muscles are doing at all times so any potential damage to this area can greatly affect one's senses. Pseudounipolar bipolar neurons Within each Somatosensory pathway there are three types of neurons: the pseudounipolar neuron, secondary afferentme neurons, and tertiary afferent neurons.
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The axon reflex arc is distinct from the spinal cord reflex arc. In the spinal cord reflex pathway the afferent neuron transmits information to spinal cord interneurons. These interneurons act collectively, process and make sense of inbound stimuli, and stimulate effector neurons acting as an integration center. The effector neurons leaving the integration center transmit a response to the original tissue the reflex arose resulting in a response.
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In the spinal cord, however, at least 75 afferent neurons are required to produce firing. This picture is further complicated by variation in time constant between neurons, as some cells can experience their EPSPs over a wider period of time than others. While in synapses in the developing brain synaptic depression has been particularly widely observed it has been speculated that it changes to facilitation in adult brains.
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He wrote a seminal paper describing a technique to record the electrical responses of deep brain structures to sensory stimuli such as a flash of light or a loud sound. The paper is highly cited, having been referenced in 384 articles by January 2019.Starzl TE, Taylor CW, Magoun HW. Collateral Afferent Excitation of Reticular Formation of Brain Stem. Journal of Neurophysiology, Nov 1951 In 1959, he gained a Markle scholarship.
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The basal ganglia contains many afferent glutamatergic inputs, with predominantly GABAergic efferent fibers, modulatory cholinergic pathways, significant dopamine in the pathways originating in the ventral tegmental area and substantia nigra, as well as various neuropeptides. Neuropeptides found in the basal ganglia include substance P, neurokinin A, cholecystokinin, neurotensin, neurokinin B, neuropeptide Y, somatostatin, dynorphin, enkephaline. Other neuromodulators found in the basal ganglia include nitric oxide, carbon monoxide, and phenylethylamine.
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Complementing this, afferent nerve fibres have been found that project to early visual areas such as the lingual gyrus from late in the dorsal (action) and ventral (perception) visual streams, as well as from the auditory association cortex. Feedback projections have also been observed in the opossum directly from the auditory association cortex to V1. This last observation currently highlights a point of controversy within the neuroscientific community. Sadato et al.
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The final product of this communication is the ability to see, hear or feel something as interpreted by the brain. Dejerine–Roussy syndrome most often compromises tactile sensation. Therefore, the damage in the thalamus causes miscommunication between the afferent pathway and the cortex of the brain, changing what or how one feels. The change could be an incorrect sensation experienced, or inappropriate amplification or dulling of a sensation.
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Upon leaving the medulla oblongata between the olive and the inferior cerebellar peduncle, the vagus nerve extends through the jugular foramen, then passes into the carotid sheath between the internal carotid artery and the internal jugular vein down to the neck, chest, and abdomen, where it contributes to the innervation of the viscera, reaching all the way to the colon. Besides giving some output to various organs, the vagus nerve comprises between 80% and 90% of afferent nerves mostly conveying sensory information about the state of the body's organs to the central nervous system. The right and left vagus nerves descend from the cranial vault through the jugular foramina, penetrating the carotid sheath between the internal and external carotid arteries, then passing posterolateral to the common carotid artery. The cell bodies of visceral afferent fibers of the vagus nerve are located bilaterally in the inferior ganglion of the vagus nerve (nodose ganglia).
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This deafferentation creates interruption of complex circuitry, which can lead to transneuronal structural degeneration. Although studies have shown that lesions can lead to transneuronal degeneration, lesions in the somatic motor system might not cause it. There is not much information on how transneuronal degeneration affects the somatic motor system . Anterograde transneuronal degeneration is not likely to happen since motor neurons are often exhibit convergence (receive input from wide variety of afferent systems).
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Neurokinin has been shown to contribute to both bradycardia and myocardial infarctions through the activation of NK2 receptors. The dual sensory-motor function of neurokinin A containing afferent neurons is a component of the intracardiac nervous system. Varicose processes of tachykinin-containing nerves are abundant in coronary arteries and in the cardiac ganglia. The diverse responses that are triggered by locally released tachykinins produce beneficial effects such as modulation of ganglion transmission.
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Obligate ram ventilation is also true of some pelagic bony fish species. The respiration and circulation process begins when deoxygenated blood travels to the shark's two-chambered heart. Here the shark pumps blood to its gills via the ventral aorta artery where it branches into afferent brachial arteries. Reoxygenation takes place in the gills and the reoxygenated blood flows into the efferent brachial arteries, which come together to form the dorsal aorta.
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This is certainly not the case. Pallidum is precisely one cerebral place where there is a dramatic change between one afferent geometry and a completely different efferent one. The inmap and the outmap are totally different. This is an indication of the fundamental role of the pallidonigral set: the spatial reorganisation of information for a particular "function", which is predictably a particular reorganisation within the thalamus preparing a distribution to the cortex.
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In contrast to the open-loop response-chaining hypothesis, Adams' closed-loop theory suggested that processing of afferent information was central in human motor control. Adams’ closed-loop theory is based on basic motor learning research that focused on slow, graded, linear positioning tasks, which involved error detection and correction to meet goal demands. To learn a movement, a “motor program” consisting of two states of memory (i.e. memory trace and perceptual trace), is required.
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A dermatome is an area of skin that is mainly supplied by afferent nerve fibres from the dorsal root of any given spinal nerve. There are 8 cervical nerves (C1 being an exception with no dermatome), 12 thoracic nerves, 5 lumbar nerves and 5 sacral nerves. Each of these nerves relays sensation (including pain) from a particular region of skin to the brain. A dermatome also refers to the part of an embryonic somite.
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Nervous System Organization - The Motor and Sensory Systems Afferent neurons are pseudounipolar neurons that have a single axon leaving the cell body dividing into two branches: the long one towards the sensory organ, and the short one toward the central nervous system (e.g. spinal cord). These cells do not have dendrites that are typically inherent in neurons. They have a smooth and rounded cell body located in the ganglia of the peripheral nervous system.
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His major contribution to the world of science is the development of a single-fiber technique for recording afferent impulses from individual sensory receptors. Paintal discovered several sensory receptors including atrial B receptors, pulmonary J-receptors, ventricular pressure receptors, stomach stretch receptors, and muscle pain receptors. They have set the beginning of new era in physiological understanding. Paintal returned to India in 1953 and joined All India Institute of Medical Sciences, New Delhi.
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Microneurography is a technique using metal electrodes to observe neural traffic of both myelinated and unmyelinated axons in efferent and afferent neurons of the skin and muscle. This technique is particularly important in research involving C fibers. Single action potentials from unmyelinated axons can be observed. Recordings from efferent postganglionic sympathetic C fibers of the muscles and skin yield insights into the neural control of autonomic effector organs like blood vessels and sweat glands.
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Glomus tumors were first described by Hoyer in 1877 while the first complete clinical description was given by Masson in 1924. Histologically, glomus tumors are made up of an afferent arteriole, anastomotic vessel, and collecting venule. Glomus tumors are modified smooth muscle cells that control the thermoregulatory function of dermal glomus bodies. As stated above, these lesions should not be confused with paragangliomas, which were formerly also called glomus tumors in now-antiquated clinical usage.
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The physiatrist, along with the rehabilitation team, work with the patient to develop specific, measurable, action-oriented, realistic, and time-centered goals. With respect to physical therapy interventions, it has been determined that repetitive task-specific sensory input can improve motor output in patients with central cord syndrome. These activities enable the spinal cord to incorporate both supraspinal and afferent sensory information to help recover motor output. This occurrence is known as "activity dependent plasticity".
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Neurons of the auditory or vestibulocochlear nerve (the eighth cranial nerve) innervate cochlear and vestibular hair cells. The neurotransmitter released by hair cells that stimulates the terminal neurites of peripheral axons of the afferent (towards the brain) neurons is thought to be glutamate. At the presynaptic juncture, there is a distinct presynaptic dense body or ribbon. This dense body is surrounded by synaptic vesicles and is thought to aid in the fast release of neurotransmitter.
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Efferent projections from the brain to the cochlea also play a role in the perception of sound. Efferent synapses occur on outer hair cells and on afferent axons under inner hair cells. The presynaptic terminal bouton is filled with vesicles containing acetylcholine and a neuropeptide called calcitonin gene-related peptide. The effects of these compounds vary, in some hair cells the acetylcholine hyperpolarized the cell, which reduces the sensitivity of the cochlea locally.
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Each arcuate artery supplies several interlobular arteries that feed into the afferent arterioles that supply the glomeruli. After filtration occurs, the blood moves through a small network of venules that converge into interlobular veins. As with the arteriole distribution, the veins follow the same pattern: the interlobular provide blood to the arcuate veins then back to the interlobar veins, which come to form the renal vein exiting the kidney for transfusion for blood.
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Obligate ram ventilation is also true of some pelagic bony fish species. The respiration and circulation process begins when deoxygenated blood travels to the shark's two-chambered heart. Here the shark pumps blood to its gills via the ventral aorta artery where it branches into afferent brachial arteries. Reoxygenation takes place in the gills and the reoxygenated blood flows into the efferent brachial arteries, which come together to form the dorsal aorta.
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Spinal nerve Typical spinal nerve location Each spinal nerve is a mixed nerve, formed from the combination of nerve fibers from its dorsal and ventral roots. The dorsal root is the afferent sensory root and carries sensory information to the brain. The ventral root is the efferent motor root and carries motor information from the brain. The spinal nerve emerges from the spinal column through an opening (intervertebral foramen) between adjacent vertebrae.
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Regardless of the anaesthetic agent (drug) used, the desired effect is to block the transmission of afferent nerve signals from peripheral nociceptors. Sensory signals from the site are blocked, thereby eliminating pain. The degree of neuronal blockade depends on the amount and concentration of local anaesthetic used and the properties of the axon. Thin unmyelinated C-fibres associated with pain are blocked first, while thick, heavily myelinated A-alpha motor neurons are blocked moderately.
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The lymph capillaries drain the lymph to larger contractile lymphatics, which have valves as well as smooth muscle walls. These are called the collecting lymphatics. As the collecting lymph vessel accumulates lymph from more and more lymph capillaries in its course, it becomes larger and is called the afferent lymph vessel as it enters a lymphs node. Here the lymph percolates through the lymph node tissue and is removed by the efferent lymph vessel.
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In this circumstance, the SPN is controlled only by spinal influences. The first couple of weeks after a spinal injury, the decreased sympathetic outflow causes reduced blood pressure and sympathetic reflex. Eventually, synaptic reorganization and plasticity of SPN develops into an overly sensitive state, which results in abnormal reflex activation of SPN due to afferent stimuli, such as bowel or bladder distension. Reflex activation results in systemic vasoconstriction below the spinal cord disruption.
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The interposed nucleus is part of the deep cerebellar complex and is composed of the globose nucleus and the emboliform nucleus. It is located in the roof (dorsal aspect) of the fourth ventricle, lateral to the fastigial nucleus. It receives its afferent supply from the anterior lobe of the cerebellum and sends output via the superior cerebellar peduncle to the red nucleus. The interposed nucleus is located in the paravermis of the cerebellum.
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The archicortex is largely made up of memorizing cells with two types of afferent synapses: excitatory and unmodifiable inhibitory synapses. Memorizing cell inhibition serves two functions; one is controlling synaptic modification conditions in the memorizing cell dendrites during learning and the other is controlling cell thresholds during recall. The archicortex may also contain codon cells. Unlike the neocortex, the archicortex lacks climbing fibers (fibers involved in the clustering part of neocortical classification).
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The initialization of sensation stems from the response of a specific receptor to a physical stimulus. The receptors which react to the stimulus and initiate the process of sensation are commonly characterized in four distinct categories: chemoreceptors, photoreceptors, mechanoreceptors, and thermoreceptors. All receptors receive distinct physical stimuli and transduce the signal into an electrical action potential. This action potential then travels along afferent neurons to specific brain regions where it is processed and interpreted.
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A painful, nociceptive stimulus stimulates primary afferent fibers and travels to the brain via transmission cells. Increasing activity of the transmission cells results in increased perceived pain. Conversely, decreasing activity of transmission cells reduces perceived pain. In the gate control theory, a closed "gate" describes when input to transmission cells is blocked, therefore reducing the sensation of pain. An open “gate” describes when input to transmission cells is permitted, therefore allowing the sensation of pain.
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Dystonia is another motor disorder that presents sensorimotor integration abnormalities. There are multiple pieces of evidence that indicate focal dystonia is related to improper linking or processing of afferent sensory information in the motor regions of the brain. For example, dystonia can be partially relieved through the use of a sensory trick. A sensory trick is the application of a stimulus to an area near to the location affected by dystonia that provides relief.
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The olfactory system is the sensory system used for olfaction, or the sense of smell. It detects volatile, airborne substances. Most sensory systems spatially segregate afferent input from primary sensory neurons to construct a topographic map that defines the location of a sensory stimulus within the environment, as well as the quality of the stimulus itself. Unlike other sensory systems, the topography in the olfactory system is not dependent on spatial properties of the stimuli.
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The glossopharyngeal nerve, known as the ninth cranial nerve (CN IX), is a mixed nerve that carries afferent sensory and efferent motor information. It exits the brainstem out from the sides of the upper medulla, just anterior (closer to the nose) to the vagus nerve. The motor division of the glossopharyngeal nerve is derived from the basal plate of the embryonic medulla oblongata, while the sensory division originates from the cranial neural crest.
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Axon reflex suggests that the afferent fiber is bifurcated before connecting to the dorsal horn. Bifurcated fibers do exist in muscle, skin, and intervertebral discs. Yet these particular neurons are rare and are not representative of the whole body. Axon-Reflex also does not explain the time delay before the appearance of referred pain, threshold differences for stimulating local and referred pain, and somatosensory sensibility changes in the area of referred pain.
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A single taste bud is innervated by several afferent nerves, while a single efferent fiber innervates several taste buds. Fungiform papillae are present on the anterior portion of the tongue while circumvallate papillae and foliate papillae are found on the posterior portion of the tongue. The salivary glands are responsible for keeping the taste buds moist with saliva. A single taste bud is composed of four types of cells, and each taste bud has between 30 and 80 cells.
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Experience- dependent plasticity is commonly studied in the barrel cortex by partially depriving it of sensory input, either by lesioning elements of the afferent pathway (e.g. the trigeminal nerve) or by ablating, plucking, or trimming some of the facial whiskers. The anatomical structure of the barrels is only affected by lesioning elements of the pathway, but innocuous forms of deprivation can induce rapid changes in the cortical map into adulthood, without any corresponding changes in the barrel structures.
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The medial geniculate nucleus (MGN) or medial geniculate body (MGB) is part of the auditory thalamus and represents the thalamic relay between the inferior colliculus (IC) and the auditory cortex (AC). It is made up of a number of sub-nuclei that are distinguished by their neuronal morphology and density, by their afferent and efferent connections, and by the coding properties of their neurons. It is thought that the MGN influences the direction and maintenance of attention.
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Trk receptors and their ligands (neurotrophins) also affect neurons' functional properties. Both NT-3 and BDNF are important in the regulation and development of synapses formed between afferent neurons and motor neurons. Increased NT-3/trkC binding results in larger monosynaptic excitatory postsynaptic potentials (EPSPs) and reduced polysynaptic components. On the other hand, increased NT-3 binding to trkB to BDNF has the opposite effect, reducing the size of monosynaptic excitatory postsynaptic potentials (EPSPs) and increasing polysynaptic signaling.
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The reticulotegmental nucleus, tegmental pontine reticular nucleus (or pontine reticular nucleus of the tegmentum) is an area within the floor of the midbrain. This area is known to affect the cerebellum with its axonal projections. These afferent connections have been proven to project not only ipsilaterally, but also to decussate and project to the contralateral side of the vermis. It has also been shown that the projections from the pontine tegmentum to the cerebellar lobes are only crossed fibers.
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The primary stage of binaural fusion, the processing of binaural signals, occurs at the SOC, where afferent fibers of the left and right auditory pathways first converge. This processing occurs because of the interaction of excitatory and inhibitory inputs in the LSO and MSO. The SOC processes and integrates binaural information, in the form of ITD and ILD, entering the brainstem from the cochleae. This initial processing of ILD and ITD is regulated by GABAB receptors.
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Reviewers have commented on the extent and excitement of the battles, and also the attention to detail. The presence of empathy (in Rhon) and anti-empathy/sadism (in Aristo) is explained by two extraneous structures in the brain, KEB and Kyle Afferent Body (KAB). The first sends out signals of emotions, while the second interprets them. The Aristos were genetically engineered for resistance to pain, and the structure that is supposed to interpret telepathic signals is defective.
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All afferent touch/vibration info ascends the spinal cord via the posterior (dorsal) column-medial lemniscus pathway via gracilis (T7 and below) or cuneatus (T6 and above). Cuneatus sends signals to the cochlear nucleus indirectly via spinal grey matter, this info is used in determining if a perceived sound is just villi noise/irritation. All fibers cross (left becomes right) in the medulla. A somatosensory pathway will typically have three neurons:Saladin KS. Anatomy and Physiology 3rd edd. 2004.
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Early electrophysiological studies in frogs report that noxious mechanical, thermal and chemical stimuli excite primary afferent fibres with slowly conducting axons. There are two types of nerve fibre relevant to pain in amphibians. Group C nerve fibres are a type of sensory nerve fibre which lack a myelin sheath and have a small diameter, meaning they have a low nerve conduction velocity. The suffering associated with burns, toothaches, or crushing injury are caused by C fibre activity.
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Vision loss often results despite correctly functioning retinal receptors. Optic nerve diseases such as optic neuritis or retrobulbar neuritis lead to dysfunction in the afferent nerve pathway once the signal has been correctly transmitted from retinal photoreceptors. Partial or total vision loss may affect every single area of a person's life. Though loss of eyesight may occur naturally as we age, trauma to the eye or exposure to hazardous conditions may also cause this serious condition.
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Pioneering experiments in cats with then-graduate student Paul Richards Burgess demonstrated the existence of a class of thinly myelinated primary-afferent fibers that only responded to noxious (nociceptive) mechanical stimulation;Mason P. Placing pain on the sensory map: Classic papers by Ed Perl and colleagues. J. Neurophysiol. 97: 1871-1873, 2007. Burgess and Perl (1967) described in depth this class of high-threshold mechanoreceptor, using “nociceptor,” a term coined by Charles Sherrington in 1906, to identify these neurons.
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Magnocellular neurosecretory cells are large neuroendocrine cells within the supraoptic nucleus and paraventricular nucleus of the hypothalamus. They are also found in smaller numbers in accessory cell groups between these two nuclei, the largest one being the nucleus circularis. There are two types of magnocellular neurosecretory cells, oxytocin-producing cells and vasopressin- producing cells, but a small number can produce both hormones. These cells are neuroendocrine neurons, are electrically excitable, and generate action potentials in response to afferent stimulation.
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Amazingly, these animals were capable of producing a functional scratch response, albeit diminished in accuracy. When afferent feedback is provided, the scratch response is more accurate in terms of accessing the stimulus site. Recordings indicate that feedback modulates the timing and intensity of scratching, in the form of phase and amplitude changes in nerve firing. In studying the scratch reflex, researchers have named a number of regions on the surface of the body as they relate to the reflex.
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Giszter, S. F., Moxon, K. A., Rybak, I. A., & Chapin, J. K. (2001). Neurobiological and neurorobotic approaches to control architectures for a humanoid motor system. Robotics and Autonomous Systems, 37(2-3), 219-235. This theory of motor action is based on the organization of cortical columns, which progressively integrate from simple sensory input into a complex afferent signals, or from complex motor programs to simple controls for each muscle fiber in efferent signals, forming a similar hierarchical structure.
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Muscle spindle discharges are sent to the spinal cord through afferent nerve fibers, where they activate monosynaptic and polysynaptic reflex arcs, causing the muscle to contract. The effects of sustained vibratory stimulation on muscle contraction, posture and kinesthetic perceptions are much more complex than merely contraction of the muscle being vibrated. Russian scientists Victor Gurfinkel, Mikhail Lebedev, Andrew Polyakov and Yuri Levick used vibratory stimulation to study human posture control and spectral characteristics of electromyographic (EMG) activity.
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Superficial neuromasts are located externally on the surface of the body, while canal neuromasts are located along the lateral lines in subdermal, fluid filled canals. Each neuromast consists of receptive hair cells whose tips are covered by a flexible and jellylike cupula. Hair cells typically possess both glutamatergic afferent connections and cholinergic efferent connections. The receptive hair cells are modified epithelial cells and typically possess bundles of 40-50 microvilli "hairs" which function as the mechanoreceptors.
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Amplitude and kinetics of the electrical signal vary as a function of position within the dendrite and signal frequency. The major trigger for CA3 discharge is the afferent input from the dentate gyrus granule cells, from which mossy fiber terminals create very complex synapses on the proximal part of the CA3 apical dendrite in the stratum lucidum. Here they contact very complex dendritic spines. Glutamate release from single terminals evokes a large non-NMDA mediated EPSP.
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A consensual response is any reflex observed on one side of the body when the other side has been stimulated. For example, if an individual's right eye is shielded and light shines into the left eye, constriction of the right pupil will occur, as well as the left. This is because the afferent signal sent through one optic nerve connects to the Edinger-Westphal nucleus, whose axons run to both the right and the left oculomotor nerves.
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It is associated with the Ib. Tendon organs signal muscle force through the entire physiological range, not only at high strain. During locomotion, Ib input excites rather than inhibits motoneurons of the receptor- bearing muscles, and it affects the timing of the transitions between the stance and swing phases of locomotion. The switch to autogenic excitation is a form of positive feedback. The ascending or afferent pathways to the cerebellum are the dorsal and ventral spinocerebellar tracts.
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The methodology was first invented by Dr. Marshall Stoller at UCSF Medical Center, San Francisco, and was first known as the SANS (Stoller Afferent Nerve Stimulator) protocol. In 2000, Dr. Stoller reported that 98 patients were treated with the SANS device with an approximate 80% success rate in treating urge incontinence syndrome, including urgency and frequency. Dr. Marshall Stoller's Guest Lecture On IC Network In a corroborative multi-center study by Govier, et al., 71% of patients achieved success.
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The CNS consists of the brain and spinal cord. The PNS consists mainly of nerves, which are enclosed bundles of the long fibers or axons, that connect the CNS to every other part of the body. Nerves that transmit signals from the brain are called motor or efferent nerves, while those nerves that transmit information from the body to the CNS are called sensory or afferent. Spinal nerves serve both functions and are called mixed nerves.
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Free nerve endings, many of which act as nociceptors, innervate the bones, ligaments, and muscles of the TMJ. The fibrocartilage that overlays the TMJ condyle is not innervated and is avascular in healthy TMJs. When bone tissue, ligaments, or muscles become inflamed or injured, sensory signals are relayed along small-diameter primary afferent nerve fibers that form the trigeminal nerve. Signals are directed through the trigeminal nerve and modulated by neuronal cell bodies in the trigeminal ganglion.
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Similar to other local anesthetics, benzonatate is a potent voltage-gated sodium channel inhibitor. After absorption and circulation to the respiratory tract, benzonatate acts as a local anesthetic, decreasing the sensitivity of vagal afferent fibers and stretch receptors in the bronchi, alveoli, and pleura in the lower airway and lung. This dampens their activity and reduces the cough reflex. Benzonatate also has central antitussive activity on the cough center in central nervous system at the level of the medulla.
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These divisions are summarized below in Divisions of the premotor cortex. The connectivity of the premotor cortex is diverse, partly because the premotor cortex itself is heterogenous and different subregions have different connectivity. Generally the premotor cortex has strong afferent (input) and efferent (output) connectivity to the primary motor cortex, the supplementary motor area, the superior and inferior parietal cortex, and prefrontal cortex. Subcortically it projects to the spinal cord, the striatum, and the motor thalamus among other structures.
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Although the exact function of the supramammillary nucleus is still not clear, it is known that the SuM plays a role in modulating theta frequencies. Because of its role in modulating hippocampal theta, it is implicated in spatial and emotional memory formation.The axons of SuM neurons make monosynaptic connections to granule cells and GABAergic interneurons in the dentate gyrus. The SuM projects it's afferent signals exclusively to the dentate gyrus and CA2 region of the hippocampus.
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As enteric afferent and efferent nerves do not protrude into the intestinal lumen, EC cells act as a form of sensory transduction. Serotonin in the ENS acts in synergy with other digestive hormones to regulate sensory and motor gastrointestinal reflexes. EC cells respond to both chemical and neurological stimuli. They are also reactive to mechanosensation, which is the case in the peristaltic reflex of the gut, and can be stimulated by a bolus moving through the bowel.
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Together with turtles, the tuatara has the most primitive hearing organs among the amniotes. There is no eardrum and no earhole, they lack a tympanum, and the middle ear cavity is filled with loose tissue, mostly adipose (fatty) tissue. The stapes comes into contact with the quadrate (which is immovable), as well as the hyoid and squamosal. The hair cells are unspecialised, innervated by both afferent and efferent nerve fibres, and respond only to low frequencies.
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One vesicle release from the presynaptic hair cell onto the postsynaptic bouton is enough to create an action potential in the auditory afferent cells. Photoreceptors allow one vesicle release for many action potential propagation. The rod terminal and cone ribbon synapse of the photoreceptors have horizontal synaptic spines expressing AMPA receptors with additional bipolar dendrites exhibiting the mGluR6 receptors. These structures allow for the binding of multiple molecules of glutamate, allowing for the propagation of many action potentials.
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Also, neurons were found to have responded strongest at 4.5 kHz, which is the frequency of the Gryllus song. Despite the type of auditory afferent, all observed neurons revealed an inverse/latency relationship. The stronger the stimulus, the shorter the time until the neuron begins to respond. The difference in the number of afferents above the threshold on a side of the animal is called population code and can be used to account for sound localization.
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The putamen is interconnected with the following structures: This is a transverse section of the striatum from a structural MR image. The striatum includes the caudate nucleus (top) and putamen (right) and the globus pallidus (left). This description is rudimentary and does not nearly exhaust even the basic established circuitry of the putamen. The cortico-subcortico-cortical circuits with putaminal involvement are dense and complicated, consisting of a wide range of axonal, dendritic, chemical, afferent, and efferent substrates.
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Each arcuate artery supplies several interlobular arteries that feed into the afferent arterioles that supply the glomeruli. Blood drains from the kidneys, ultimately into the inferior vena cava. After filtration occurs, the blood moves through a small network of small veins (venules) that converge into interlobular veins. As with the arteriole distribution, the veins follow the same pattern: the interlobular provide blood to the arcuate veins then back to the interlobar veins, which come to form the renal veins which exiting the kidney .
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Only two patients are recorded as having no complications.; ; ; The theoretical basis of Burckhardt's action rested on three propositions. The first was that mental illness had a physical basis and that disordered minds were merely a reflection of disordered brains. Next, the associationist viewpoint of nerve functioning which conceived the nervous system as operating according to the following threefold division of labor: an input (or sensory or afferent) system, a connecting system which processed information and an output (or efferent or motor) system.
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Lumbar plexus and its branches. Since the Lumbar plexus and Sacral plexus are interconnected, they are sometimes referred to as the Lumbosacral plexus. The intercostal nerves that give rami to the chest and to the upper parts of the abdominal wall efferent motor innervation and to the pleura and peritoneum afferent sensory innervation are the only ones that do not originate from a plexus. The ventral rami of L1-L5 spinal nerves with a contribution of T12 form Lumbar plexus.
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The infection stimulates the production of 5' hydroxytryptamine (serotonin). This activates vagal afferent nerves, which in turn activates the cells of the brain stem that control the vomiting reflex. Healthy enterocytes secrete lactase into the small intestine; milk intolerance due to lactase deficiency is a symptom of rotavirus infection, which can persist for weeks. A recurrence of mild diarrhoea often follows the reintroduction of milk into the child's diet, due to bacterial fermentation of the disaccharide lactose in the gut.
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Under conditions of jamming, the P-unit fires on the amplitude peaks of the beat cycle where the two waves constructively interfere. So, a combined stimulus-EOD signal will cause T-units to fire at the intermediate frequency, and cause P-unit firing to increase and decrease periodically with the beat.Scheich, H., Bullock, T., Hamstra, Jr., R. (1973) Coding properties of two classes of afferent nerve fibers: high-frequency electroreceptors in the electric fish, Eigenmannia. J. Neurophysiol. 36:39-60.
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Striatal axons may in fact simply cross the dendrite and give a single synapse. More frequently the striatal axon curves its course and follow the dendrite forming "parallel contacts" for a rather short distance. The average length of parallel contacts was found to be 55 micrometres with 3 to 10 boutons (synapses). In another type of axonal pattern the afferent axon bifurcates and gives two or more branches, parallel to the dendrite, thus increasing the number of synapses given by one striatal axon.
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Next, the renal portal system, which involves the afferent veins, obtains blood from the ischiadic and external iliac veins. The renal portal valve is situated between the renal portal vein and the common iliac vein which leads to the posterior vena cava. Closing of the valve directs the blood to flow into the renal portal vein, and when the valve is open, blood flows into the vena cava. After entering the renal portal vein, blood enters the peritubular blood supply.
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The fine touch (epicritic) is conducted by fibers of the medial lemniscus. The medial lemniscus is formed by the axons of the neurons of the gracilis and cuneatus nuclei of the medulla oblongata which receive information about light touch, vibration and conscient proprioception from the gracilis and cuneatus fasciculus of the spinal cord. This fasciculus receive the axons of the first order neuron which is located in the dorsal root ganglion that receives afferent fibers from receptors in the skin, muscles and joints.
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In parallel with this work at the University of North Carolina, Perl and co-workers sought to correlate how stimulating individual cutaneous nociceptors in awake human volunteers is experienced by these subjects; the resulting study proved the linkage between activation of identified nociceptors and the subjective experience of pain in humans.Konietzny F, Perl ER, Trevino D, Light A, and Hensel H. Sensory experiences in man evoked by intraneural electrical stimulation of intact cutaneous afferent fibers. Exp. Br. Res. 42: 219-222, 1981.
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These studies revealed for the first time a functional organization to the central termination pattern of unmyelinated afferents with different response profiles to skin stimulation.Sugiura Y, Lee CL, and Perl, ER. Central projections of identified, unmyelinated (C) afferent fibers innervating mammalian skin. Science 234: 358-361, 1986. Experiments performed by Christopher Honda, Siegfried Mense, and Perl in the early 1980s demonstrated that neurons located in specific areas of the cat thalamus were responsive to noxious stimulation of the skin of the hindlimb.
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Thus, any stretching of a muscle automatically signals a reflexive contraction of that muscle, without any central control. As the name and the description implies, monosynaptic reflexes depend on a single synaptic connection between an afferent sensory neuron and efferent motor neuron. In general the actions of monosynaptic reflexes are fixed and cannot be controlled or influenced by intention or instruction. However, there is some evidence to suggest that the gain or magnitude of these reflexes can be adjusted by context and experience.
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Readings of afferent discharges from C nociceptors identified by marking method have also proved helpful in revealing the mechanisms underlying sensations such as itch. Unfortunately, interpretation of the microneurographic readings can be difficult because axonal membrane potential can not be determined from this method. A supplemental method used to better understand these readings involves examining recordings of post-spike excitability and shifts in latency; these features are associated with changes in membrane potential of unmyelinated axons like C fibers. Moalem-Taylor et al.
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Neuropeptide B is a short biologically active peptide whose precursor in humans is encoded by the NBP gene. Neuropeptide B acts via two G protein- coupled receptors, neuropeptide B/W receptors, called NPBW1 and NPBW2 encoded by the genes NPBWR1 and NPBWR2, respectively. Neuropeptide B is thought to be associated with the regulation of feeding, neuroendocrine system, memory, learning and in the afferent pain pathway. It is expressed throughout the CNS with high levels in the substantia nigra, hypothalamus, hippocampus, and spinal cord.
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Glomus type I cells are chemoreceptors which monitor arterial blood for the partial pressure of oxygen (pO2), partial pressure of carbon dioxide (pCO2) and pH. Glomus type I cells are secretory sensory neurons that release neurotransmitters in response to hypoxemia (low pO2), hypercapnia (high pCO2) or acidosis (low pH). Signals are transmitted to the afferent nerve fibers of the sinus nerve and may include dopamine, acetylcholine, and adenosine. This information is sent to the respiratory center and helps the brain to regulate breathing.
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The torus semicircularis is a region of the vertebrate midbrain that contributes to auditory perception, studied most often in fish and amphibians. Neurons from the medulla project to the nucleus centralis and the nucleus ventrolateralis in the torus semicircularis, providing afferent auditory and hydrodynamic information. Research suggests that these nuclei interact with each other, suggesting that this area of the brain is bimodally sensitive. In the Gymnotiform fish, which are weakly electric fish, the torus semicircularis was observed to exhibit laminar organization.
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During a shadowing task, the process of perceiving speech and a subsequent response by the production of speech does not occur separately, it would partially overlap. The auditory system shifts between a translation stage of perceiving phonemes and a choice phase of anticipating the following phonemes to create an immediate response. This period of overlap occurs in 20 – 90 ms, depending on the combination of vowels with consonants. The translation phase involves afferent codes that uses the auditory system and neural networks.
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Nerve fiber innervation is much denser for inner hair cells than for outer hair cells. A single inner hair cell is innervated by numerous nerve fibers, whereas a single nerve fiber innervates many outer hair cells. Inner hair cell nerve fibers are also very heavily myelinated, which is in contrast to the unmyelinated outer hair cell nerve fibers. The region of the basilar membrane supplying the inputs to a particular afferent nerve fibre can be considered to be its receptive field.
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This nerve may be involved by the glomus jugulare tumour. Laryngeal cancer can present with pain behind the ear and in the ear - this is a referred pain through the vagus nerve to the nerve of Arnold. In a small portion of individuals, the auricular nerve is the afferent limb of the Ear-Cough or Arnold Reflex. Physical stimulation of the external acoustic meatus innervated by the auricular nerve elicits a cough, much like the other cough reflexes associated with the vagus nerve.
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The reason for this lies in the mechanism of filtration of BUN and creatinine. Renal Plasma Flow (RPF) is decreased due to hypoperfusion which results in a proportional decrease in GFR. In turn, the decreased flow and pressure to the kidney will be sensed by baroreceptors in the Juxtaglomerular (JG) Cells of the afferent arteriole. If the decrease in blood pressure is systemic (rather than occlusion of the renal artery) baroreceptors in the carotid sinus and aortic arch will be stimulated.
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This leads to sympathetic nerve activation, resulting in renin secretion through β 1 -receptors. Constriction of the afferent arterioles causes a decrease in the intraglomerular pressure, reducing GFR proportionally. Renin is the main effector of the juxtaglomerular baroreceptors. Renin is secreted from granules in the JG cells, and once in the blood stream, it acts as a protease to convert angiotensinogen to angiotensin I, which is converted by angiotensin converting enzyme, to angiotensin II, which, in turn, stimulates aldosterone release.
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This hypothesis remains controversial." His objective was, "To briefly review and update experimental evidence concerning reflex effects of vertebral subluxations, particularly concerning peripheral nervous system responses to vertebral subluxations. Data source: Information was obtained from chiropractic or, scientific peer-reviewed literature concerning human or animal studies of neural responses to vertebral subluxation, vertebral displacement or movement, or both." He concluded, "Animal models suggest that vertebral displacements and putative vertebral subluxations may modulate activity in group I to IV afferent nerves.
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The glomerulus is the network known as a tuft, of filtering capillaries located at the vascular pole of the renal corpuscle in Bowman's capsule. Each glomerulus receives its blood supply from an afferent arteriole of the renal circulation. The glomerular blood pressure provides the driving force for water and solutes to be filtered out of the blood plasma, and into the interior of Bowman's capsule, called Bowman's space. Only about a fifth of the plasma is filtered in the glomerulus.
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In humans and other mammals, neurons in the PMC send descending excitatory projections to spinally located parasympathetic neurons controlling the detrusor muscle of the bladder and inhibitory interneurons regulating Onuf's nucleus. Additionally, the PMC receives ascending input from the level of the lumbosacral spinal cord. During bladder filling, neurons within the PMC are turned off. However, at a critical level of bladder distention the afferent information arising from mechanoreceptors in the detrusor switches the PMC on and enhances its activity.
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Anatomically, the afferent limb consists of the retina, the optic nerve, and the pretectal nucleus in the midbrain, at level of superior colliculus. Ganglion cells of the retina project fibers through the optic nerve to the ipsilateral pretectal nucleus. The efferent limb is the pupillary motor output from the pretectal nucleus to the ciliary sphincter muscle of the iris. The pretectal nucleus projects crossed and uncrossed fibers to the ipsilateral and contralateral Edinger-Westphal nuclei, which are also located in the midbrain.
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The image on the left side depicts the dorsal column pathway for vibration perception. The sensory conduction pathway that allows for cognitive recognition of vibration occurs through afferent neurons, also known as sensory neurons. The outside stimulus is a vibration that activates one of the three encapsulated nerve endings based upon where the sensation is felt. The intensity of the vibration must cause the neuron(s) to reach or surpass a threshold in order for an action potential to be propagated.
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During development, the branch of an afferent article may travel unusually far in the nervous system. Thus, in an individual with a fully developed nervous system, the stimulus at the end of one branch may be interpreted as coming from a point of ending in another, distant, part of the body. Again, research has not been done to prove this hypothesis as valid or invalid. There is an untested hypothesis that claims that referred itch uses the spinocervical tract pathway.
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Again, depending on the stress and strain the muscles sustains, this afferent and efferent coordination will measure the "stretch of the spring" and communicate the results to the central nervous system. A similar structure attaching one end to muscle and the other end to a tendon is known as a Golgi tendon organ. However, Golgi tendon organs differ from nuclear chain and nuclear bag fibers in that they are considered in series rather than in parallel to the muscle fibers.
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This is the nerve along which the sensory cells (the hair cells) of the inner ear transmit information to the brain. It consists of the cochlear nerve, carrying information about hearing, and the vestibular nerve, carrying information about balance. It emerges from the pontomedullary junction and exits the inner skull via the internal acoustic meatus (or internal auditory meatus) in the temporal bone. The vestibulocochlear nerve carries axons of type SSA, special somatic afferent, which carry the modalities of hearing and equilibrium.
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The nucleus raphe obscurus, despite the implications of its name, has some very specific functions and connections of afferent and efferent nature. The nucleus raphes obscurus projects to the cerebellar lobes VI and VII and to crus II along with the nucleus raphe pontis. The nucleus raphes obscurus has also been implicated in the modulation of the hypoglossal nerve. It has been observed that the ablation of this nucleus causes a change in the firing pattern of this cranial nerve.
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There are several proposed mechanisms for referred pain. Currently there is no definitive consensus regarding which is correct. The cardiac general visceral sensory pain fibers follow the sympathetics back to the spinal cord and have their cell bodies located in thoracic dorsal root ganglia 1-4(5). As a general rule, in the thorax and abdomen, general visceral afferent (GVA) pain fibers follow sympathetic fibers back to the same spinal cord segments that gave rise to the preganglionic sympathetic fibers.
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Motor fibers are carried via the facial nerve proper. The greater petrosal nerve, which carries preganglionic parasympathetic fibers, emerges from the anterior aspect of the ganglion. The motor fibers of the facial nerve proper and parasympathetic fibers to the submandibular and pterygopalatine ganglia do not synapse in the geniculate ganglion. The afferent fibers carrying pain, temperature, and touch from the posterior auricular nerve, as well as those carrying special sensory (taste) fibers from the tongue (via the chorda tympani), do not synapse in the geniculate ganglion.
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The myenteric plexus functions as a part of the enteric nervous system (digestive system). The enteric nervous system can and does function autonomously, but normal digestive function requires communication links between this intrinsic system and the central nervous system. The ENS contains sensory receptors, primary afferent neurons, interneurons, and motor neurons. The events that are controlled, at least in part, by the ENS are multiple and include motor activity, secretion, absorption, blood flow, and interaction with other organs such as the gallbladder or pancreas.
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By using the same approach to reconstruct the solitary tract and its gustatory nuclei,Eyriès C, Chouard CH. Le faisceau solitaire. Ann. Oto-Laryng. (Paris) 1965; 82: 15-36. he observed that the nucleus of the last brachial nerve, the pneumogastric nerve, extended a long way down, undoubtedly causing afferent sensitivity of the enteric and airway pathways. This hypothesis has been the electro-physiological existence of which was recently demonstrated within the intestines, and which could potentially play a role in certain forms of diabetes.
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The paramedian nucleus receives afferents mostly from the fastigial nucleus in the cerebellum and the cerebral cortex; however, the projections from the spinal cord are very sparse. The descending afferent connections come mostly from the frontal and parietal lobes; however the pontine reticular formation also sends projections to the paramedian reticular nucleus. There are also very sparse innervations from the superior colliculus. Lesions in the paramedian reticular nucleus have been shown to cause a stereotyped increase in the random patterns of motion in rats.
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The spinal cord functions primarily in the transmission of nerve signals from the motor cortex to the body, and from the afferent fibers of the sensory neurons to the sensory cortex. It is also a center for coordinating many reflexes and contains reflex arcs that can independently control reflexes. It is also the location of groups of spinal interneurons that make up the neural circuits known as central pattern generators. These circuits are responsible for controlling motor instructions for rhythmic movements such as walking.
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The somatosensory system is a part of the sensory nervous system. The somatosensory system is a complex system of sensory neurons and neural pathways that responds to changes at the surface or inside the body. The axons (as afferent nerve fibers) of sensory neurons connect with, or respond to, various receptor cells. These sensory receptor cells are activated by different stimuli such as heat and nociception, giving a functional name to the responding sensory neuron, such as a thermoreceptor which carries information about temperature changes.
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The extraglomerular mesangial cells are found between the afferent and efferent arterioles towards the vascular pole of the glomerulus. The extraglomerular mesangial cells are adjacent to the intraglomerular mesangial cells that are located inside the glomerulus and in between the capillaries. The primary function of mesangial cells is to remove trapped residues and aggregated protein from the basement membrane thus keeping the filter free of debris. The contractile properties of mesangial cells have been shown to be insignificant in changing the filtration pressure of the glomerulus.
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Each neuron in the nucleus has one long axon that projects to the posterior pituitary gland, where it gives rise to about 10,000 neurosecretory nerve terminals. The magnocellular neurons are electrically excitable: In response to afferent stimuli from other neurons, they generate action potentials, which propagate down the axons. When an action potential invades a neurosecretory terminal, the terminal is depolarised, and calcium enters the terminal through voltage-gated channels. The calcium entry triggers the secretion of some of the vesicles by a process known as exocytosis.
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Chronic stimulation of the STN, called deep brain stimulation (DBS), is used to treat patients with Parkinson disease. The first to be stimulated are the terminal arborisations of afferent axons, which modify the activity of subthalamic neurons. However, it has been shown in thalamic slices from mice, that the stimulus also causes nearby astrocytes to release adenosine triphosphate (ATP), a precursor to adenosine (through a catabolic process). In turn, adenosine A1 receptor activation depresses excitatory transmission in the thalamus, thus mimicking ablation of the subthalamic nucleus.
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When halteres are experimentally induced to flap, volleys of action potentials within the haltere nerve occur in synchrony with the haltere-beat frequency. When flies are then rotated, these volleys break down, likely in response to different groups of sensilla being activated to inform the fly of its recently changed body position. Haltere afferents have also been shown to terminate in the mesothoracic neuropil where flight muscle neurons are located. Haltere afferent activity responding to rotations and wing steering behavior converge in this processing region.
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Cortical radial arteries, formerly known as interlobular arteries, are renal blood vessels given off at right angles from the side of the arcuate arteries looking toward the cortical substance. The interlobular arteries pass directly outward between the medullary rays to reach the fibrous tunic, where they end in the capillary network of this part. These vessels do not anastomose with each other, but form end-arteries. In their outward course, they give off lateral branches, which are the afferent arterioles that supply the renal corpuscles.
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Diagram showing the basic physiologic mechanisms of the kidney In renal physiology, ultrafiltration occurs at the barrier between the blood and the filtrate in the glomerular capsule (Bowman's capsule) in the kidneys. As in nonbiological examples of ultrafiltration, pressure (in this case blood pressure) and concentration gradients lead to a separation through a semipermeable membrane (provided by the podocytes). The Bowman's capsule contains a dense capillary network called the glomerulus. Blood flows into these capillaries through the afferent arterioles and leaves through the efferent arterioles.
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Thanks to fusimotor activation, the afferent signal from muscle spindles remains efficient in monitoring large changes of muscle length without turning silent during muscle shortening. On the other hand, very small intramuscular events are monitored as well, thanks to the extreme sensitivity of the sense organ. An example is the small pulsatile component of the muscle contraction which is due to a periodic fluctuation at 8–10 Hz of the motor command. These small variations are insentient but readily monitored by the population of spindle afferents.
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Hereditary motor and sensory neuropathies (HMSN) is a name sometimes given to a group of different neuropathies which are all characterized by their impact upon both afferent and efferent neural communication. HMSN are characterised by atypical neural development and degradation of neural tissue. The two common forms of HMSN are either hypertrophic demyelinated nerves or complete atrophy of neural tissue. Hypertrophic condition causes neural stiffness and a demyelination of nerves in the peripheral nervous system, and atrophy causes the breakdown of axons and neural cell bodies.
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They also discovered that the 'all or nothing' protopathic system was the first to recover after the operation so that painful stimulus was the first to register. Head spent the next few years following up on his findings. With Theodore Thompson he grouped afferent impulses within the spinal cord whilst studying the brain for its pain centres. During the First World War his studies continued as he worked with G. Riddoch to test reflex activities of isolated portions of spines subjected to gunshot wounds.
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The physiological basis for the RAIR is poorly understood, but it is thought to involve a coordinated response by the internal anal sphincter to rectal distention with recovery of anal pressure from the distal to the proximal sphincter. Mediated by the autonomic nervous system, the afferent limb of this reflex depends upon an intact network of interstitial cells of Cajal in the internal anal sphincter. These cells, which are mediated at least in part by nitric oxide, provide inhibitory innervation of the internal anal sphincter.
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Somatosensory evoked potential (SEP or SSEP) is the electrical activity of the brain that results from the stimulation of touch. SEP tests measure that activity and are a useful, noninvasive means of assessing somatosensory system functioning. By combining SEP recordings at different levels of the somatosensory pathways, it is possible to assess the transmission of the afferent volley from the periphery up to the cortex. SEP components include a series of positive and negative deflections that can be elicited by virtually any sensory stimuli.
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In clinical trials reductions in hand tremors were reported following noninvasive median and radial nerve stimulation. Transcutaneous Afferent Patterned Stimulation (TAPS) is a tremor-customized therapy, based on the patient's measured tremor frequency, and is delivered transcutaneously to the median and radial nerves of a patient's wrist. The patient specific TAPS stimulation is determined through a calibration process performed by the accelerometer and microprocessor on the device. The Cala ONE delivers TAPS in a wrist-worn device that is calibrated to treat tremor symptoms.
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It is difficult to rely on symptoms to diagnose a thoracic aortic injury. However some symptoms do include severe chest pain, cough, shortness of breath, difficulty swallowing due to compression of the esophagus, back pain, and hoarseness due to involvement of the recurrent laryngeal nerve. There might be external signs such as bruising on the anterior chest wall due to a traumatic injury. Clinical signs are uncommon and nonspecific but can include generalized hypertension due to the injury involving the sympathetic afferent nerves in the aortic isthmus.
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Research attention is currently focused not only on external perception processes, but also to "interoception", considered as the process of receiving, accessing and appraising internal bodily signals. Maintaining desired physiological states is critical for an organism's well being and survival. Interoception is an iterative process, requiring the interplay between perception of body states and awareness of these states to generate proper self-regulation. Afferent sensory signals continuously interact with higher order cognitive representations of goals, history, and environment, shaping emotional experience and motivating regulatory behavior.
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Classified as a sensory circumventricular organ (along with the SFO and AP), the vascular organ of lamina terminalis (VOLT) is situated in the anterior wall of the third ventricle. Characteristically of the CVOs, it lacks the tight endothelial blood brain barrier. The vascular organ is further characterized by the afferent inputs from the subfornical organ (SFO), the median pre-optic nucleus (MnPO) region, the brainstem, and even the hypothalamus. Conversely, the vascular organ of the lamina terminalis maintains efferent projections to the stria medullaris and basal ganglia.
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The celiac ganglion is part of the sympathetic prevertebral chain possessing a great variety of specific receptors and neurotransmitters such as catecholamines, neuropeptides, and nitric oxide and constitutes a modulation center in the pathway of the afferent and efferent fibers between the central nervous system and the ovary. The main preganglion neurotransmitter of the celiac ganglion is acetylcholine, yet the celiac ganglion-mesenteric complex also contain α and β adrenergic receptors and is innervated by fibers of adrenergic nature that come from other preaortic ganglia.
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Like enamel, dentin is avascular. Nutrition for odontoblasts within the dentin comes through the dentinal tubules from tissue fluid that originally traveled from the blood vessels located in the adjacent pulp tissue. Within each dentinal tubule is a space of variable size containing dentinal fluid, an odontoblastic process, and possibly an afferent axon (see next discussion). The dentinal fluid in the tubule presumably also includes the tissue fluid surrounding the cell membrane of the odontoblast, which is continuous from the cell body in the pulp.
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The central nervous system controls muscle spindle sensitivity via the fusimotor system. It consists of muscle spindles along with fusimotor neurons - beta motor neurons and gamma motor neurons. Because beta motor neurons innervate extrafusal as well as intrafusal muscle fibers, they are more specifically named skeletofusimotor neurons. Gamma motor neurons are the efferent (sending signals away from the central nervous system) part of the fusimotor system, whereas muscle spindles are the afferent part, as they send signals relaying information from muscles toward the spinal cord and brain.
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The optic nerve, or more precisely, the photosensitive ganglion cells through the retinohypothalamic tract, is responsible for the afferent limb of the pupillary reflex; it senses the incoming light. The oculomotor nerve is responsible for the efferent limb of the pupillary reflex; it drives the iris muscles that constrict the pupil. Pathways in the Ciliary ganglion. #Retina: The pupillary reflex pathway begins with the photosensitive retinal ganglion cells, which convey information via the optic nerve, the most peripheral, distal, portion of which is the optic disc.
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The vague and poorly defined sensation as well as its temporal nature, characteristic of visceral pain, is due to the low density of sensory innervation of viscera and the extensive divergence of visceral input within the central nervous system (CNS). The phenomenon of referred pain is secondary to the convergence of visceral afferent (sensory) nerve fibers entering the spinal cord at the same level as the superficial, somatic structures experiencing the pain. This leads to a misinterpretation of incoming signals by higher brain centers.
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These findings highlighted the novel role of projection neurons in guiding the laminar fate of cortical interneurons. In 2013, Arlotta and Rouaux showed that they could reprogram neurons post-mitotically. Arlotta and Rouaux show that exposure to Fezf2 can reprogram post-mitotic callosal neurons to become layer V/VI CFu neurons during a specific post-mitotic developmental window. This work was followed up by Zhanlei Ye and Mohammed Mostajo-Radji who showed that afferent inhibitory synapses from parvalbumin-positive interneurons could be rewired upon pyramidal neuron reprogramming.
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Water velocity is thus related to the amount of deflection of certain stereocilia, and sensory cells send information about this deflection to the brain via firing rates of afferent nerves. Cephalopods, including the squid Loligo vulgaris and cuttlefish Sepia officinalis, have ciliated sensory cells arranged in lines at different locations on the body.Budelmann, B U, and H Bleckmann. “A lateral line analogue in cephalopods: water waves generate microphonic potentials in the epidermal head lines of Sepia and Lolliguncula.” Journal of Comparative Physiology A 164 (1988): 1-5.
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Most ASIC are expressed in the nervous system. ASIC1, ASIC2, ASIC2b, and ASIC4 are commonly expressed in both the central and peripheral nervous system, while ASIC1b and ASIC3 are typically only located in the peripheral. In the peripheral nervous system, ASICs are located within the cell bodies of postsynaptic membranes and sensory nerve terminals. Additionally, ASICs are typically found in afferent nerve fibers of the skin, muscles, joints, and viscera, where they have been discovered to be associated with pain, taste, and gastrointestinal functions.
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Histological section of a normal lymph node Lymphocyte surrounded by red blood cells. The lymph nodes, the spleen and Peyer's patches, are known as secondary lymphoid organs. Lymph nodes are found between lymphatic ducts and blood vessels. Afferent lymphatic vessels bring lymph fluid from the peripheral tissues to the lymph nodes. The lymph tissue in the lymph nodes consists of immune cells (95%), for example lymphocytes, and stromal cells (1% to 5%) The genesis of lymph nodes begins within the blood and the lymphatic system.
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Afferent projections to the rat nuclei raphe magnus, raphe pallidus and reticularis gigantocellularis pars demonstrated by iontophoretic application of choleratoxin (subunit b). Journal of Chemical Neuroanatomy Volume 13, Issue 1, June 1997, Pages 1-21 All of these brain areas influence the main function of the nucleus raphe magnus. The main function of the nucleus raphe magnus is mostly pain mediation; in fact it sends projections to the dorsal horn of the spinal cord to directly inhibit pain. The nucleus raphe magnus releases serotonin when stimulated.
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The periaqueductal grey matter, an area of the brain involved in mediating analgesia, sends efferent connections to the nucleus raphe magnus when it is stimulated by opiates (endogenous or otherwise). Electrical stimulation of the PAG produces analgesia, as well as administration of morphine to the PAG or nucleus raphe magnus. The antinociceptic effects of electrical stimulation of the PAG can be blocked by administering naloxone, an opiate antagonist, to the nucleus raphe magnus. Similarly, afferent fibres from the spinothalamic tract synapse at the periaqueductal grey matter.
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In the summer of 1948 Perl had served as a clerk on the Harvard Medical Service of Boston City Hospital, where his interactions with neurologist and neuroscience researcher Derek Denny-Brown steered Perl toward a career in neurophysiology. Perl began a postdoctoral fellowship in the laboratory of Philip Bard in the Department of Physiology at Johns Hopkins University in the fall of 1950; there he met neuroanatomist Jerzy Rose and neurophysiologist Vernon Mountcastle, who would become a lifelong mentor in surgical and electrophysiological recording techniques. During this time Perl became interested in how the activity of C-fiber afferent neurons was transferred to the cerebral cortex, a project that proved difficult, but which influenced his interest in these unmyelinated afferent fibers and their then- presumed participation in the detection and transmission of pain and temperature sensations to the brain. Perl was called to active duty as a naval physician in January, 1952, and served as a medical officer at the Walter Reed Army Institute of Research, where he joined a neuroscience research group led by David McKenzie Rioch and staffed by Robert Galambos, Michael Fuortes, Walle Nauta, and David Whitlock.
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The subthalamic nucleus essentially provides the excitement needed to drive the globus pallidus. Injury to this area or its efferent or afferent connections can induce this disorder contralateral to the side of the lesion. The structure itself is a regulator of motor function and is also involved in associative and limbic functions. It was traditionally thought that the disorder was only caused by injury to the subthalamic nucleus, but later studies have shown that damage to other basal ganglia regions can also be responsible for causing this disorder.
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The trigeminal nerve carries afferent fibres from the follicles into the brainstem where they connect to neurons in four different trigeminal nerve nuclei: principal, interpolar, oral, and caudal. Projections from the trigeminal nuclei to the thalamus are split into pathways designated lemniscal, extralemniscal, and paralemniscal. In the lemniscal pathway, axons from the principal trigeminal nucleus cross over the midline and project to “barreloids” in the thalamus, specifically in the dorsomedial section of the ventroposterior medial nucleus (VPMdm). Neurons in VPMdm project mainly to barrels in layer 4 of primary somatosensory cortex (S1).
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Glomerular pathology progresses to glomerulosclerosis, and eventually the kidney tubules may also become ischemic and gradually atrophic. The kidney lesion associated with malignant hypertension consists of fibrinoid necrosis of the afferent arterioles, sometimes extending into the glomerulus, and may result in focal necrosis of the glomerular tuft. Clinically, macroalbuminuria (a random urine albumin/creatinine ratio > 300 mg/g) or microalbuminuria (a random urine albumin/creatinine ratio 30–300 mg/g) are early markers of kidney injury. These are also risk factors for kidney disease progression and for cardiovascular disease.
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Autonomic functions of the brain include the regulation, or rhythmic control of the heart rate and rate of breathing, and maintaining homeostasis. Blood pressure and heart rate are influenced by the vasomotor centre of the medulla, which causes arteries and veins to be somewhat constricted at rest. It does this by influencing the sympathetic and parasympathetic nervous systems via the vagus nerve. Information about blood pressure is generated by baroreceptors in aortic bodies in the aortic arch, and passed to the brain along the afferent fibres of the vagus nerve.
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The dentatothalamic fibers also cross over and ascend to synapse in the ventral intermediate (VI) and ventral anterior (VA) nuclei of the thalamus. The fastigioreticular fibers enter the reticular formation of the midbrain, pons, and medulla oblongata. Afferent pathways include the anterior spinocerebellar and tectocerebellar tracts. The fibers of the anterior spinocerebellar tract originate in Clarke's column of the spinal cord and cross in the anterior white commissure to the lateral funiculus, where they ascend to upper pontine levels before crossing back to enter the cerebellum through the superior peduncle.
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All of these sinuses drain into the efferent lymphatic vessels to exit the node at the hilum on the concave side. These are channels within the node lined by endothelial cells along with fibroblastic reticular cells, allowing for the smooth flow of lymph. The endothelium of the subcapsular sinus is continuous with that of the afferent lymph vessel and also with that of the similar sinuses flanking the trabeculae and within the cortex. These vessels are smaller and don't allow the passage of macrophages so that they remain contained to function within a lymph node.
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Exposure to cereulide causes loss of the membrane potential and uncoupling of oxidative phosphorylation in the mitochondria.News on cereulide, the emetic toxin of Bacillus Cereus The nausea and vomiting is believed to be caused by cereulide's binding and activation of 5-HT3 receptors, leading to increased afferent vagus nerve stimulation. Cereulide is a cyclic dodecadepsipeptide resembling valinomycin; it contains three repeats of four amino acids: D-Oxy-Leu—D-Ala—L-Oxy-Val—L-Val. It is produced by a dedicated non-ribosomal peptide synthesis (NRPS) system in B. cereus.
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Recent studies indicate that TRPA1 is activated by a number of reactive (allyl isothiocyanate, cinnamaldehyde, farnesyl thiosalicylic acid, formalin, hydrogen peroxide, 4-hydroxynonenal, acrolein, and tear gases) and non-reactive compounds (nicotine, PF-4840154) and is thus considered as a "chemosensor" in the body. TRPA1 is co-expressed with TRPV1 on nociceptive primary afferent C-fibers in humans. This sub-population of peripheral C-fibers is considered important sensors of nociception in humans and their activation will under normal conditions give rise to pain. Indeed, TRPA1 is considered as an attractive pain target.
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The lingual nerve supplies general somatic afferent innervation from the mucous membrane of the anterior two-thirds (body) of the tongue, while the posterior one-third (root) is innervated by the glossopharyngeal. It also carries nerve fibers that are not part of the trigeminal nerve, including the chorda tympani nerve of the facial nerve, which provides special sensation (taste) to the anterior 2/3 part of the tongue as well as parasympathetic and sympathetic fibers. The submandibular ganglion is suspended by two nerve filaments from the lingual nerve.
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The juxtaglomerular cells (JG cells, or granular cells) are cells in the kidney that synthesize, store, and secrete the enzyme renin. They are specialized smooth muscle cells mainly in the walls of the afferent arterioles (and some in the efferent arterioles) that deliver blood to the glomerulus. In synthesizing renin, they play a critical role in the renin–angiotensin system and thus in autoregulation of the kidney. Juxtaglomerular cells secrete renin in response to a drop in pressure detected by stretch receptors in the vascular walls, or when stimulated by macula densa cells.
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Each canal has a widened base, called an ampulla, that houses specialized sensory hair cells. Fluid in these canals surrounds the hair cells, and moves across them as the head moves to gather information about the movement and position of the body. The hair cells are covered in tiny sensory hairs called stereocilia, which are sensitive to displacement forces as the body is moved in different positions. When the head is moved, the force moves the hair cells forward, which sends signals to afferent fibers and on to the brain.
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The response-chaining, or reflex- chaining hypothesis, proposed by William James (1890), was one of the earliest descriptions of movement control. This open-loop hypothesis postulated that movements required attention only for initiation of the first action.p. 165 As such, each subsequent movement was thought to be automatically triggered by response-produced afferent information from the muscles. Although feedback is involved in this process, ongoing movements cannot be modified if there are unexpected changes in the environment; feedback is not compared to some internally generated reference value for error checking.
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The internal granular layer of the cortex, also commonly referred to as the granular layer of the cortex, is the layer IV in the subdivision of the mammalian cortex into 6 layers. The adjective internal is used in opposition to the external granular layer of the cortex, the term granular refers to the granule cells found here. This layer receives the afferent connections from the thalamus and from other cortical regions and sends connections to the other layers. The line of Gennari (occipital stripe) is also present in this layer.
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Mesangial cells have irregular shapes with flattened-cylinder-like cell bodies and processes at both ends containing actin, myosin and actinin, giving mesangial cells contractile properties. The anchoring filaments from mesangial cells to the glomerular basement membrane can alter capillary flow by changing glomerular ultrafiltration surface area. Extraglomerular mesangial cells are in close connection to afferent and efferent arteriolar cells by gap junctions, allowing for intercellular communication. Mesangial cells are separated by intercellular spaces containing extracellular matrix called the mesangial matrix that is produced by the mesangial cells.
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Vasopressin (antidiuretic hormone, ADH) is released in response to solute concentration in the blood, decreased blood volume, or blood pressure. Some other inputs come from the brainstem, including from some of the noradrenergic neurons of the nucleus of the solitary tract and the ventrolateral medulla. However, many of the direct inputs to the supraoptic nucleus come from neurons just outside the nucleus (the "perinuclear zone"). Of the afferent inputs to the supraoptic nucleus, most contain either the inhibitory neurotransmitter GABA or the excitatory neurotransmitter glutamate, but these transmitters often co-exist with various peptides.
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Carotid and aortic bodies are clusters of cells located on the common carotid artery and the aortic arch, respectively. Each of these peripheral chemoreceptors is composed of type I glomus cells and glia-like type II cells. The type-I cells transduce the signals from the bloodstream and are innervated by afferent nerve fibers leading back to (in the carotid body) the carotid sinus nerve and then on to the glossopharyngeal nerve and medulla of the brainstem. The aortic body, by contrast, is connected to the medulla via the vagus nerve.
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Renal sympathetic denervation (RSDN), is a minimally invasive, endovascular catheter based procedure using radiofrequency ablation or ultrasound ablation aimed at treating resistant hypertension (high blood pressure not controlled by medication). Nerves in the wall of the renal artery are ablated by applying radiofrequency pulses or ultrasound to the renal arteries. This causes reduction of sympathetic afferent and efferent activity to the kidney and blood pressure can be decreased. Early data from international clinical trials without sham controls was promising - demonstrating large blood pressure reductions in patients with treatment-resistant hypertension.
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The results showed a significant decrease in intracortical inhibition, which resulted in a slowdown of interstimulus intervals by 3 ms. In addition to its proximity to and association with the limbic system and the amygdala in particular, which plays a key role in emotional experience, the anterior cingulate cortex shares afferent and efferent pathways with a number of thalamic nuclei as well as the posterior cingulate and part of some parietal, frontal and supplementary motor cortex.Cohen et al. (1999). Alteration of Intention and Self-Initiated Action Associated With Bilateral Anterior Cingulotomy.
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Diuretics act by lowering water and sodium levels; this causes more reabsorption of lithium in the proximal tubules so that the removal of lithium from the body is less, leading to increased blood levels of lithium. ACE inhibitors have also been shown in a retrospective case-control study to increase lithium concentrations. This is likely due to constriction of the afferent arteriole of the glomerulus, resulting in decreased glomerular filtration rate and clearance. Another possible mechanism is that ACE inhibitors can lead to a decrease in sodium and water.
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All of these sensations travel along the same general pathways towards the brain. One pathwaydorsal column-medial lemniscus pathwaybegins with sensation from the periphery being sent via afferent nerve fiber of the dorsal root ganglion (first order neuron) through the spinal cord to the dorsal column nuclei (second order neuron) in the brainstem. The second order neuron's projection decussates at the medulla through medial lemniscus to the third order neurons in the thalamus. The third order neuron's axon terminates at the primary somatosensory cortex of the parietal lobe.
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The first mechanism has to do with cortical centers responsible for visual processing. Irritation of visual association cortices (Brodmann's areas 18 and 19) cause complex visual hallucinations. The second mechanism is deafferentation, the interruption or destruction of the afferent connections of nerve cells, of the visual system, caused by lesions, leading to the removal of normal inhibitory processes on cortical input to visual association areas, leading to complex hallucinations as a release phenomenon. The third mechanism has to do with the reticular activating system, which plays a role in the maintenance of arousal.
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Joints are controlled by two opposing sets of muscles called extensors and flexors that must work in synchrony to allow proper and desired movement. When a muscle spindle is stretched and the stretch reflex is activated, the opposing muscle group must be inhibited to prevent from working against the agonist muscle. The spinal interneuron called Ia inhibitory interneuron is responsible for this inhibition of the antagonist muscle. The Ia afferent of the muscle spindle enters the spinal cord, and one branch synapses on to the alpha motor neuron that causes the agonist muscle to contract.
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Efferent nerve fibers refer to axonal projections that exit a particular region; as opposed to afferent projections that arrive at the region. These terms have a slightly different meaning in the context of the peripheral nervous system (PNS) and central nervous system (CNS). The efferent fiber is a long process projecting far from the neuron's body that carries nerve impulses away from the central nervous system toward the peripheral effector organs (mainly muscles and glands). A bundle of these fibers is called a motor nerve or an efferent nerve.
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Reflex arc demonstrated When a reflex arc in an animal consists of only one sensory neuron and one motor neuron, it is defined as monosynaptic, referring to the presence of a single chemical synapse. In the case of peripheral muscle reflexes (patellar reflex, achilles reflex), brief stimulation to the muscle spindle results in contraction of the agonist or effector muscle. By contrast, in polysynaptic reflex pathways, one or more interneurons connect afferent (sensory) and efferent (motor) signals. All but the most simple reflexes are polysynaptic, allowing processing or inhibition of polysynaptic reflexes within the brain.
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Inputs to the claustrum are organized by modality, which include visual, auditory and somatomotor processing areas. In the same way that the morphology of neurons in the spinal cord is indicative of function (i.e. rexed laminae), the visual, auditory and somatomotor regions within the claustrum share similar neurons with specific functional characteristics. For example, the portion of the claustrum that processes visual information (primarily synthesizing afferent fibers concerned with our peripheral visual field) is comprised by a majority of binocular cells that have “elongated receptive fields and no orientation selectivity.
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The fibres of the LOCS also appear to be arranged in a tonotopic fashion. However, it is not known whether the characteristic frequencies of the LOCS fibres coincide with the characteristic frequencies of the primary afferent neurons, since attempts to selectively stimulate the fibres of the LOCS have been largely unsuccessful. Intrinsic LOCS derived axons travel only approximately 1 µm within the organ of Corti, generally spiraling apically. They give off a small tuft of synaptic boutons that is compact in its extent, often involving less than 10 IHCs.
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Another aspect that plays a role in neuropathic pain is the transient receptor channel called TRPA1. This channel is known to have influenced chronic pain injuries and diseases such as inflammation, diabetes, fibromyalgia, bronchitis, and emphysema. WDR neurons are a huge part of the somatosensory system, helping to send and receive signals based on sensory changes in the body. The TRPA1 channel has been closely associated with temperature and pain sensation in primary afferent sensory neurons and are largely found in nociceptive sensory neurons in the dorsal root ganglia.
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The ghrelin receptor GHS-R1a (a splice-variant of the growth hormone secretagogue receptor, with the GHS-R1b splice being inactive) is involved in mediating a wide variety of biological effects of ghrelin, including: stimulation of growth hormone release, increase in hunger, modulation of glucose and lipid metabolism, regulation of gastrointestinal motility and secretion, protection of neuronal and cardiovascular cells, and regulation of immune function. They are present in high density in the hypothalamus and pituitary, on the vagus nerve (on both afferent cell bodies and efferent nerve endings) and throughout the gastrointestinal tract.
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Initially, there is constriction of the efferent arterioles and dilation of afferent arterioles, with resulting glomerular capillary hypertension and hyperfiltration; this gradually changes to hypofiltration over time. Concurrently, there are changes within the glomerulus itself: these include a thickening of the basement membrane, a widening of the slit membranes of the podocytes, an increase in the number of mesangial cells, and an increase in mesangial matrix. This matrix invades the glomerular capillaries and produces deposits called Kimmelstiel-Wilson nodules. The mesangial cells and matrix can progressively expand and consume the entire glomerulus, shutting off filtration.
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The first-order neurons are sensory neurons located in the dorsal root ganglia, that send their afferent fibers through the two dorsal columns – the gracile fasciculus, or gracile tract, and the cuneate fasciculus, or cuneate tract. The first-order axons make contact with second- order neurons of the dorsal column nuclei (the gracile nucleus and the cuneate nucleus) in the lower medulla. The second-order neurons send their axons to the thalamus. The third-order neurons are in the ventral nuclear group in the thalamus and fibres from these ascend to the postcentral gyrus.
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The olfactory nerve is typically considered the first cranial nerve, or simply CN I, that contains sensory nerve fibers relating to the sense of smell. The afferent nerve fibers of the olfactory receptor neurons transmit nerve impulses about odors to the central nervous system (olfaction). Derived from the embryonic nasal placode, the olfactory nerve is somewhat unusual among cranial nerves because it is capable of some regeneration if damaged. The olfactory nerve is sensory in nature and originates on the olfactory mucosa in the upper part of the nasal cavity.
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Therefore, the pressure increase is slight until the organ is relatively full. The bladder's smooth muscle has some inherent contractile activity; however, when its nerve supply is intact, stretch receptors in the bladder wall initiate a reflex contraction that has a lower threshold than the inherent contractile response of the muscle. Action potentials carried by sensory neurons from stretch receptors in the urinary bladder wall travel to the sacral segments of the spinal cord through the pelvic nerves. Since bladder wall stretch is low during the storage phase, these afferent neurons fire at low frequencies.
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CART is an anorectic peptide and is widely expressed in both the central and peripheral nervous systems, particularly concentrated in the hypothalamus. CART is also expressed outside of the nervous system in pituitary endocrine cells, adrenomedullary cells, islet somatostatin cells, and in rat antral gastrin cells. Other structures and pathways associated with CART expression include the mesolimbic pathway (linking the ventral tegmental area to the nucleus accumbens) and amygdala. CART is also found in a subset of retinal ganglion cells (RGCs), the primary afferent neurons in the retina.
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Some researchers believe that the use of somatic markers (i.e., afferent feedback) would be a very inefficient method of influencing behavior. Damasio's notion of the as-if experience dependent feedback route, whereby bodily responses are re- represented utilizing the somatosensory cortex (postcentral gyrus), also proposes an inefficient method of affecting explicit behavior. Rolls (1999) stated that; "it would be very inefficient and noisy to place in the execution route a peripheral response, and transducers to attempt to measure that peripheral response, itself a notoriously difficult procedure" (p. 73).
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Edward Taub (born 1931) is a behavioral neuroscientist currently based at the University of Alabama at Birmingham. He became interested in behaviorism while studying philosophy at Columbia University, and went on to study under Fred Keller and Wiliam N. Schoenfeld, the experimental psychologists. He took a job as a research assistant in a neurology lab to gain more understanding of the nervous system, and became involved in deafferentation experiments with monkeys. An afferent nerve is a sensory nerve that conveys impulses from the skin and other sensory organs to the spine and the brain.
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The gracile nucleus is medial to the cuneate nucleus; its neurons receive afferent input from dorsal root ganglia sensory neurons subserving the lower trunk and limbs. The gracile nucleus and gracile fasciculus carry epicritic, kinesthetic, and conscious proprioceptive information from the lower part of the body (below the level of T6 in the spinal cord). Because of the large population of neurons in the gracile nucleus they give rise to a raised area called the gracile tubercle on the posterior side of the closed medulla at the floor of the fourth ventricle.
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The vasomotor tone is decreased in the area affected by the neurolysis, which in addition to arteriovenous shunting, create a light pink appearance within the affected area. Lumbar sympathetic neurolysis alters the ischemic rest pain transmission by changing norepinephrine and catecholamine levels or by disturbing afferent fibers. This procedure is mainly used only when other feasible approaches to pain management are unable to be used. Lumbar sympathetic neurolysis is performed by using absolute alcohol, but other chemicals such as phenol, or other techniques such as radiofrequency or laser ablation have been studied.
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The type I fibres are thicker than the type II fibres and may also differ in how they innervate the inner hair cells. Neurons with large calyceal endings ensure preservation of timing information throughout the ITD pathway. Next in the pathway is the cochlear nucleus, which receives mainly ipsilateral (that is, from the same side) afferent input. The cochlear nucleus has three distinct anatomical divisions, known as the antero-ventral cochlear nucleus (AVCN), postero- ventral cochlear nucleus (PVCN) and dorsal cochlear nucleus (DCN) and each have different neural innervations.
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Increased blood volume results in increased venous return to the heart, which leads to increased firing of B-fibers. B-fibers send signals to the brain (the afferent pathway of the neural portion of the Bainbridge reflex), which then modulates both sympathetic and parasympathetic pathways to the SA node of the heart (the efferent pathway of the neural portion of the Bainbridge reflex), causing an increase in heart rate. "Effects on cardiac contractility and stroke volume are insignificant." Bainbridge reflex can be blocked by atropine and can be abolished by cutting the vagus nerve.
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In addition, the facial nerve receives taste sensations from the anterior two-thirds of the tongue via the chorda tympani. Taste sensation is sent to the gustatory portion (superior part) of the solitary nucleus. General sensation from the anterior two-thirds of tongue are supplied by afferent fibers of the third division of the fifth cranial nerve (V-3). These sensory (V-3) and taste (VII) fibers travel together as the lingual nerve briefly before the chorda tympani leaves the lingual nerve to enter the tympanic cavity (middle ear) via the petrotympanic fissure.
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The second Kedem–Katchalsky equation explains the trans endothelial transport of solutes, J_s . Glomerular capillaries have a continuous glycocalyx layer in health and the total transendothelial filtration rate of solvent ( J_v ) to the renal tubules is normally around 125 ml/ min (about 180 litres/ day). Glomerular capillary J_v is more familiarly known as the glomerular filtration rate (GFR). In the rest of the body's capillaries, J_v is typically 5 ml/ min (around 8 litres/ day), and the fluid is returned to the circulation via afferent and efferent lymphatics.
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The fornix (meaning "arch" in Latin) is a C-shaped bundle of nerve fibers in the brain that acts as the major output tract of the hippocampus. The fornix also carries some afferent fibers to the hippocampus from structures in the diencephalon and basal forebrain. The fornix is part of the limbic system. While its exact function and importance in the physiology of the brain are still not entirely clear, it has been demonstrated in humans that surgical transection – the cutting of the fornix along its body – can cause memory loss.
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When the cell swells, ATP escapes through a basolateral, stretch-activated, non-selective Maxi-Anion channel. The ATP is subsequently converted to adenosine by ecto-5′-nucleotidase. # Adenosine constricts the afferent arteriole by binding with high affinity to the A1 receptors a Gi/Go. Adenosine binds with much lower affinity to A2A and A2B receptors causing dilation of efferent arterioles. #The binding of adenosine to the A1 receptor causes a complex signal cascade involving the Gi subunit deactivating Ac, thus reducing cAMP and the Go subunit activating PLC, IP3 and DAG.
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Once it became apparent that interoceptive receptors are present in many tissues of the body other researchers began to investigate afferent body-to-brain signals, mainly by conducting animal experiments to see if interoceptive conditioning was possible. Using principles of Pavlovian conditioning, different physiological systems in dogs were perturbed to elicit a conditioned response to food. For example, in one experiment, dogs’ pelvises were distended using infusions of solution when food was presented to them. After rounds of pairing the two, salivation occurred without presenting food once the pelvis was distended.
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The cupula, and the stereocilia within, are moved by a certain amount depending on the movement of the surrounding water. Afferent nerve fibers are excited or inhibited depending on whether the hair cells they arise from are deflected in the preferred or opposite direction. Lateral line receptors form somatotopic maps within the brain informing the fish of amplitude and direction of flow at different points along the body. These maps are located in the medial octavolateral nucleus (MON) of the medulla and in higher areas such as the torus semicircularis.
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2018 As an example of a spinal reflex, it results in a fast response that involves an afferent signal into the spinal cord and an efferent signal out to the muscle. The stretch reflex can be a monosynaptic reflex which provides automatic regulation of skeletal muscle length, whereby the signal entering the spinal cord arises from a change in muscle length or velocity. It can also include a polysynaptic component, as in the tonic stretch reflex. When a muscle lengthens, the muscle spindle is stretched and its nerve activity increases.
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As one important mechanism, adaptation processes in the auditory brain that influence the dynamic range of neural responses are assumed to be distorted by irregular input from the inner ear. This is mainly caused by hearing loss related damage in the inner ear. The mechanism behind hyperacusis is not currently known, but it is suspected to be caused by damage to the inner ear and cochlea. It is theorized that type II afferent fibers become excited after damage to hair cells and synapses, triggering a release of ATP in response.
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The sensory function of the trigeminal nerve is to provide tactile, proprioceptive, and nociceptive afference to the face and mouth. Its motor function activates the muscles of mastication, the tensor tympani, tensor veli palatini, mylohyoid and the anterior belly of the digastric. The trigeminal nerve carries general somatic afferent fibers (GSA), which innervate the skin of the face via ophthalmic (V1), maxillary (V2) and mandibular (V3) divisions. The trigeminal nerve also carries special visceral efferent (SVE) axons, which innervate the muscles of mastication via the mandibular (V3) division.
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Patients who have malignant gliomas of the optic nerve have rapidly progressive, painful visual loss accompanied by signs of an optic neuropathy. Initial visual loss may be unilateral or bilateral (chiasmal involvement), but rapid progression to bilateral blindness and death are constant features. Depending on the initial location of the tumor, visual loss may be accompanied by exophthalmos, extraocular motility Optic nerve melanocytoma does not usually produce symptoms or grow. If they slowly grow, optic nerve melanocytoma can produce afferent pupillary defects (30%), subretinal fluid (10%), and an enlarged blind spot (75%).
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The hypersensitivity of vagal afferent nerves causes refractory or idiopathic cough. Arnold's nerve ear-cough reflex though uncommon is a manifestation of a vagal sensory neuropathy and this is the cause of a refractory chronic cough that can be treated with gabapentin.The cough is triggered by mechanical stimulation of the external auditory meatus and accompanied by other neuropathic features such as throat irritation (laryngeal paresthesia) and cough triggered by exposure to nontussive triggers such as cold air and eating (termed allotussia). These features suggest a neuropathic origin to the cough.
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During development, semaphorins and their receptors may be involved in the sorting of pools of motor neurons and the modulation of pathfinding for afferent and efferent axons from and to these pools. For instance, Sema3a repels axons from the dorsal root ganglia, facial nerves, vagal nerves, olfactory-sensory, cortical nerves, hippocampal nerves and cerebellar nerves. Class 3 semaphorins have an important function after traumatic central nervous system injuries, such as spinal cord injury. They regulate neuronal and non-neuronal cells associated with the traumatic injury due to their presence in the scar tissue.
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The physiological change from a state of deep sleep to wakefulness is reversible and mediated by the ARAS. The ventrolateral preoptic nucleus (VLPO) of the hypothalamus inhibits the neural circuits responsible for the awake state, and VLPO activation contributes to the sleep onset. During sleep, neurons in the ARAS will have a much lower firing rate; conversely, they will have a higher activity level during the waking state. In order that the brain may sleep, there must be a reduction in ascending afferent activity reaching the cortex by suppression of the ARAS.
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This represents one of the earliest theories on the subject of referred pain. It is based on the work of W.A. Sturge and J. Ross from 1888 and later TC Ruch in 1961. Convergent projection proposes that afferent nerve fibers from tissues converge onto the same spinal neuron, and explains why referred pain is believed to be segmented in much the same way as the spinal cord. Additionally, experimental evidence shows that when local pain (pain at the site of stimulation) is intensified the referred pain is intensified as well.
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According to hyperexcitability, new receptive fields are created as a result of the opening of latent convergent afferent fibers in the dorsal horn. This signal could then be perceived as referred pain. Several characteristics are in line with this mechanism of referred pain, such as dependency on stimulus and the time delay in the appearance of referred pain as compared to local pain. However, the appearance of new receptive fields, which is interpreted to be referred pain, conflicts with the majority of experimental evidence from studies including studies of healthy individuals.
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Bronchospasm may resolve spontaneously in 1–2 hours, or in about 50% of subjects, may become part of a 'late' response, where this initial insult is followed 3–12 hours later with further bronchoconstriction and inflammation.Murray and Nadel's Textbook of Respiratory Medicine, 4th Ed. Robert J. Mason, John F. Murray, Jay A. Nadel, 2005, Elsevier pp. 334 The normal caliber of the bronchus is maintained by a balanced functioning of the autonomic nervous system, which both operates reflexively. The parasympathetic reflex loop consists of afferent nerve endings which originate under the inner lining of the bronchus.
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The vagus, or tenth cranial nerve serves to identify the relationship between visceral experiences and the vagus nerve's parasympathetic control of the heart, lungs, and digestive tract. The theory was introduced in 1994 by Dr. Stephen Porges, director of the Brain-Body Center at the University of Illinois at Chicago. As has been established since the early days of neuroanatomy, the Autonomic nervous system encompasses nerve fibers transmitting information from the body toward the brain, called afferent influences. According to polyvagal theory, this effect has been observed and demonstrated by adaptive reactivity dependent on the neural circuits' phylogenetical development.
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She values her independence and prefers enjoying charms of her provider slaves to an arranged Highton marriage. She is beautiful, very intelligent but ambitious, intrigant, unscrupulous and calculating. When we are first introduced to her, she is already over 100 years old (but looks young due to advanced anti-aging treatments) and a wealthy, powerful and dangerous woman. Tarquine is also one of the very few Aristos who had the Kyle Afferent Body removed from her brain because she began to hate how her transcending inflicted pain on others but could not resist the temptation of transcendence.
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The sensory modality that is detected by the afferent fibers is an important factor to consider because it determines the pathway that the dorsal root ganglion neurons will take within the central nervous system. The sensory neurons coming from the body synapse in the dorsal horn of the spinal cord, bringing in information about touch sensations (epicritic), or modalities of pain (protopathic). While both types of sensory neurons must first synapse in the dorsal horn of the spinal cord, the area of the dorsal horn where they synapse is different. Their pathway to the thalamus is also different.
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Basal ganglia (red) and related structures (blue) shown within the brain The dorsolateral striatum is associated with the acquisition of habits and is the main neuronal cell nucleus linked to procedural memory. Connecting excitatory afferent nerve fibers help in the regulation of activity in the basal ganglia circuit. Essentially, two parallel information processing pathways diverge from the striatum. Both acting in opposition to each other in the control of movement, they allow for association with other needed functional structures One pathway is direct while the other is indirect and all pathways work together to allow for a functional neural feedback loop.
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Following the work of Robert Whytt and Marshall Hall, Laycock studied the reflex arc in relation to the nervous system. While Hall believed that the reflex arc was mediated by the spinal cord, separate from the cerebrum, Laycock argued that the brain underwent the same reflex patterns as the rest of the nervous system. After learning the German language, he translated books by Johann August Unzer, who studied afferent and efferent reflexes. Unzer centralised the nervous system in the spinal cord, such that reflexes could occur even without a functional brain, which only controls conscious activity.
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The interposed nucleus is smaller than the dentate nucleus but larger than the fastigial nucleus and functions to modulate muscle stretch reflexes of distal musculature. It is located dorsal to the fourth ventricle and lateral to the fastigial nucleus; it receives afferent neuronal supply from the anterior lobe of the cerebellum and sends output via the superior cerebellar peduncle and the red nucleus. The fastigial nucleus is the most medial efferent cerebellar nucleus, targeting the pontine and medullary reticular formation as well as the vestibular nuclei. This region deals with antigravity muscle groups and other synergies involved with standing and walking.
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The brain and the spinal cord are the essential components of the central nervous system and it is responsible for the integration of the signals received from the afferent nerves and initiates action. The nerve cells, known as neurons, carry impulses throughout the body and the nerve impulses are carried along the axon. These microscopic nerve fibers, where the action potential occurs, are protected by a white, fatty tissue that surrounds and insulates it, known as the myelin sheath. This insulation helps the axon of a nerve cell with the conduction and speed of the signal along the axon.
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The reflex is impaired in the person whose abdominals and respiratory muscles are weak. This problem can be caused by disease conditions that lead to muscle weakness or paralysis, by prolonged inactivity, or as outcome of surgery involving these muscles. Bed rest interferes with the expansion of the chest and limits the amount of air that can be taken into the lungs in preparation for coughing, making the cough weak and ineffective. This reflex may also be impaired by damage to the internal branch of the superior laryngeal nerve which relays the afferent branch of the reflex arc.
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The lateral spinothalamic tract (or lateral spinothalamic fasciculus), which is a part of the anterolateral system, is a bundle of afferent nerve fibers ascending through the white matter of the spinal cord, carrying sensory information to the brain. It carries pain, crude touch and temperature sensory information (protopathic sensation) to the thalamus. It is composed primarily of fast- conducting, sparsely myelinated A delta fibers and slow-conducting, unmyelinated C fibers. These are secondary sensory neurons which have already synapsed with the primary sensory neurons of the peripheral nervous system in the posterior horn of the spinal cord (one of the three grey columns).
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At the point where the afferent arterioles enter the glomerulus and the efferent arteriole leaves it, the tubule of the nephron touches the arterioles of the glomerulus from which it arose. At this location, in the wall of the distal convoluted tubule, there is a modified region of tubular epithelium called the macula densa. Cells in the macula densa respond to changes in the sodium chloride levels in the distal tubule of the nephron via the tubuloglomerular feedback (TGF) loop. The macula densa's detection of elevated sodium chloride, which leads to an increase in GFR, is based on the concept of purinergic signaling.
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The PVN receives afferent inputs from many brain regions and different parts of the body, by hormonal control. Among these, inputs from neurons in structures adjacent to the anterior wall of the third ventricle (the "AV3V region") carry information about the electrolyte composition of the blood, and about circulating concentrations of such hormones as angiotensin and relaxin, to regulate the magnocellular neurons. Inputs from the brainstem (the nucleus of the solitary tract) and the ventrolateral medulla carry information from the heart and stomach. Inputs from the hippocampus to the CRH neurones are important regulators of stress responses.
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Often a larger reflex response will be observed when the patient is occupied with the maneuver: "A weak or apparently missing reflex could be triggered by afferent activity resulting from such muscle tension. This is the true explanation for the maneuver, not a diversion of the patient’s attention – a misconception that can be heard even today." This effect was first observed in the late 19th century by Hungarian physician Ernő Jendrassik, after whom it was named. This maneuver is particularly useful in that even if the patient is aware of the maneuver's purpose, it still functions properly.
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One feature of the scratch reflex is that supraspinal structures are not necessary for the generation of the reflex. The scratch response is programmed into the spinal cord, and can be produced in spinal animals. Another feature of the scratch reflex is that the spinal CPGs which generate and maintain the reflex are capable of producing the reflex in the absence of movement-related sensory feedback. This discovery was made while studying animals with silenced afferent neurons from the scratching limb, meaning no movement-related sensory feedback was available to the spinal circuits driving the scratch.
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Therefore, T cells need a region where they can go to sample foreign antigens that have entered the body. When an APC, such as a dendritic cell, binds a foreign antigen it becomes activated and moves into the lymph nodes (sites for antigen sampling by T cells) via afferent lymphatic vessels. Naïve T cells in the circulation regularly move through the lymph nodes via HEV in order to scan the APC for foreign antigens. When they encounter such an antigen, the cell becomes activated, resulting in the immune system mounting a response against the causative agent of the infection.
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Inulin is uniquely treated by nephrons in that it is completely filtered at the glomerulus but neither secreted nor reabsorbed by the tubules. This property of inulin allows the clearance of inulin to be used clinically as a highly accurate measure of glomerular filtration rate (GFR) — the rate of plasma from the afferent arteriole that is filtered into Bowman's capsule measured in ml/min. It is informative to contrast the properties of inulin with those of para-aminohippuric acid (PAH). PAH is partially filtered from plasma at the glomerulus and not reabsorbed by the tubules, in a manner identical to inulin.
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Enriched housing provides the opportunity for exercise and exposure to multimodal stimuli. The increased visual, physical, and cognitive stimulation all translates into more neuronal activity and synaptic communication, which can produce structural or molecular activity-dependent alterations. Sensory inputs from environmental stimuli are initially processed by the cortex before being transmitted to the hippocampus along an afferent pathway, suggesting the activity-mediated effects of enrichment can be far-reaching within the brain. BDNF expression is significantly enhanced by environmental enrichment and appears to be the primary source of the ability of environmental enrichments to enhance cognitive processes.
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A wide variety of electrode designs have been researched, tested, and manufactured. These electrodes lie on a spectrum varying in degrees of invasiveness. Research in this area seeks to address issues centered around peripheral nerve/tissue damage, access to efferent and afferent signals, and selective recording/stimulation of nerve tissue. Ideally peripheral nerve interfaces are optimally designed to interface with biological constraints of peripheral nerve fibers, match the mechanical and electrical properties of the surrounding tissue, biocompatible with minimal immune response, high sensor resolution, are minimally invasive, and chronically stable with low signal-to-noise ratios.
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As a result of this, impulses from the skin that pass through it are exaggerated or disordered so that a stimulus that would not usually provoke a painful reaction does so. Head also became increasingly interested in the mental changes brought on by visceral disease and he based his Goulstonian Lectures before the Royal College of Physicians on this topic. For the next twelve years, Head devoted himself to the study of the physiological basis for sensation. To do this he studied the manner in which afferent impulses subserving sensation are integrated and conducted to the forebrain.
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Vagovagal reflex refers to gastrointestinal tract reflex circuits where afferent and efferent fibers of the vagus nerve coordinate responses to gut stimuli via the dorsal vagal complex in the brain. The vagovagal reflex controls contraction of the gastrointestinal muscle layers in response to distension of the tract by food. This reflex also allows for the accommodation of large amounts of food in the gastrointestinal tracts. The vagus nerve, composed of both sensory afferents and parasympathetic efferents, carries signals from stretch receptors, osmoreceptors, and chemoreceptors to dorsal vagal complex where the signal may be further transmitted to autonomic centers in the medulla.
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Using an immobilized fish to prevent extraneous stimulation, a metal ball was vibrated at different frequencies. Utilizing single cell measurements with a microelectrode, responses were recorded and used to construct tuning curves, which revealed frequency preferences and two main afferent nerve types. One variety is attuned to collect mechanoreceptive information about acceleration, responding to stimulation frequencies between 30–200 Hz. The other type is sensitive to velocity information and is most receptive to stimulation below <30 Hz. This suggests a more intricate model of reception than was previously considered. The efferent synapses to hair cells are inhibitory and utilize acetylcholine as a transmitter.
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The proportion of fibres in the MOCS and LOCS also varies between species, but in most cases the fibres of the LOCS are more numerous.Robertson et al., 1989 In humans, there are an estimated (average) 1,000 LOCS fibres and 360 MOCS fibres, however the numbers vary between individuals. The MOCS gives rise to a frequency-specific innervation of the cochlea, in that MOC fibres terminate on the outer hair cells at the place in the cochlea predicted from the fibres’ characteristic frequency, and are thus tonotopically organised in the same fashion as the primary afferent neurons.
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When the infected mosquito has its next blood meal, W. bancrofti larvae are deposited from the mouthparts onto the skin of the prospective host and migrate through microcuts in the dermis or the tract created by the proboscis into the bloodstream of the new human host. The larvae move through the lymphatic system to regional lymph nodes, predominantly in the legs and genital area. The larvae develop into adult worms over the course of a year, and reach sexual maturity in the afferent lymphatic vessels. After mating, the adult female worm can produce thousands of microfilariae that migrate into the bloodstream.
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An example of this is when a person steps on a nail: The leg that is stepping on the nail pulls away, while the other leg takes the weight of the whole body. The crossed extensor reflex is contralateral, meaning the reflex occurs on the opposite side of the body from the stimulus. To produce this reflex, branches of the afferent nerve fibers cross from the stimulated side of the body to the contralateral side of the spinal cord. There, they synapse with interneurons, which, in turn, excite or inhibit alpha motor neurons to the muscles of the contralateral limb.
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The endocrine system consists of numerous glands throughout the body that produce and secrete hormones of diverse chemical structure, including peptides, steroids, and neuroamines. Collectively, hormones regulate many physiological processes. Oxytocin and vasopressin (also called anti-diuretic hormone), the two neurohypophysial hormones of the posterior pituitary gland (the neurohypophysis), are secreted from the nerve endings of magnocellular neurosecretory cells into the systemic circulation. The cell bodies of the oxytocin and vasopressin neurons are in the paraventricular nucleus and supraoptic nucleus, respectively, and the electrical activity of these neurons is regulated by afferent synaptic inputs from other brain regions.
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Hyperfiltration is one of the earliest features of DN. Several mechanisms have been proposed to cause hyperfiltration. One of these mechanisms is that as glomeruli becomes hypertrophied, filtration surface area initially increases. Another possible mechanism is that abnormal vascular control in diabetic nephropathy leads to a reduction in afferent glomerular arteriolar resistance and an increase in efferent glomerular arteriolar resistance, leading to a net increase in renal blood flow (RBF) and glomerular filtration rate (GFR). Glomerular hyperfiltration and an aberrant regulation of RAAS lead to increased intraglomerular pressure, causing stress on the endothelial cells, the mesangial cells and the podocytes.
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The crossed extensor reflex is another escape reflex, but it's a type of withdrawal reflex. It is a contralateral reflex that allows for the affected limb to have the flexor muscles contract and the extensor muscles to relax while the unaffected limb has the flexor muscles relax and the extensor muscles to contract. For example, stepping on a piece of glass causes the affected leg to be lifted or withdrawn and the unaffected leg to carry the additional burden of weight and maintain postural support. In this example, the afferent nerve fibers are stimulated on the right foot.
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This phenomenon is called primary afferent depolarization (PAD). Despite the depolarized potential, this still results in a reduction of neurotransmitter release and thus is still inhibition. There are three hypotheses which propose mechanisms behind this paradox: # The depolarized membrane causes inactivation of voltage-gated sodium channels on the terminals and therefore the action potential is prevented from propagating # Open GABA receptor channels act as a shunt, whereby current flows out of instead of concluding at the terminals #The depolarized membrane causes inactivation of voltage-gated calcium channels, preventing calcium influx at the synapse (which is imperative for neurotransmission).
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Recent research suggested the existence of an additional feedforward motif linking TSH release to deiodinase activity in humans. The existence of this TSH-T3 shunt could explain why deiodinase activity is higher in hypothyroid patients and why a minor fraction of affected individuals may benefit from substitution therapy with T3. Convergence of multiple afferent signals in the control of TSH release including but not limited to T3, cytokines and TSH receptor antibodies may be the reason for the observation that the relation between free T4 concentration and TSH levels deviates from a pure loglinear relation that has previously been proposed.
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Activation of aortic smooth muscle doesn't significantly alter the lumenal diameter but serves to increase the viscoelasticity of the vascular wall. In the digestive tract, smooth muscle contracts in a rhythmic peristaltic fashion, rhythmically forcing foodstuffs through the digestive tract as the result of phasic contraction. A non-contractile function is seen in specialized smooth muscle within the afferent arteriole of the juxtaglomerular apparatus, which secretes renin in response to osmotic and pressure changes, and also it is believed to secrete ATP in tubuloglomerular regulation of glomerular filtration rate. Renin in turn activates the renin–angiotensin system to regulate blood pressure.
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Furthermore, JG cells contain beta-1 adrenergic receptors, and so activation of the sympathetic nervous system will further stimulate renin release. Thus, a drop in blood pressure results in preferential vasodilation of the afferent arterioles, increasing renal blood flow (RBF), renal plasma flow (RPF) and GFR due to greater blood flow to the glomerulus. Note that there is no change in filtration fraction, as both GFR and RPF are increased. It also results in the release of renin, which, through the renin–angiotensin system, causes constriction of the efferent arterioles, which ultimately increases hydrostatic pressure in the glomerulus.
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Since both the short and long ciliary nerves carry the afferent limb of the corneal reflex, one can test the integrity of the nasociliary nerve (and, ultimately, the trigeminal nerve) by examining this reflex in the patient. Normally both eyes should blink when either cornea (not the conjunctiva, which is supplied by the adjacent cutaneous nerves) is irritated. If neither eye blinks, then either the ipsilateral nasociliary nerve is damaged, or the facial nerve (CN VII, which carries the efferent limb of this reflex) is bilaterally damaged. If only the contralateral eye blinks, then the ipsilateral facial nerve is damaged.
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As the study of the cochlea should fundamentally be focused at the level of hair cells, it is important to note the anatomical and physiological differences between the hair cells of various species. In birds, for instance, instead of outer and inner hair cells, there are tall and short hair cells. There are several similarities of note in regard to this comparative data. For one, the tall hair cell is very similar in function to that of the inner hair cell, and the short hair cell, lacking afferent auditory-nerve fiber innervation, resembles the outer hair cell.
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Papilledema as a result of dural sinus thrombosis and atrophy resulting from retinal disease, have been characterized as secondary causes of optic nerve atrophy in Behçet's disease. Signs and symptoms of acute optic neuropathy include painless loss of vision which may affect either one or both eyes, reduced visual acuity, reduced color vision, relative afferent pupillary defect, central scotoma, swollen optic disc, macular edema, or retrobulbar pain. When these symptoms occur with concurrent mucocutaneous ulcerations, they raise suspicion of acute optic neuropathy in Behçet's Disease. Progressive optic atrophy may result in decreased visual acuity or color vision.
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A still image from a 3D medical animation showing afferent vessels The lymphatic vessels (or lymph vessels or lymphatics) are thin-walled vessels (tubes) structured like blood vessels, that carry lymph. As part of the lymphatic system, lymph vessels are complementary to the cardiovascular system. Lymph vessels are lined by endothelial cells, and have a thin layer of smooth muscle, and adventitia that binds the lymph vessels to the surrounding tissue. Lymph vessels are devoted to the propulsion of the lymph from the lymph capillaries, which are mainly concerned with absorption of interstitial fluid from the tissues.
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Muscle coordination, muscle memory, and innate game awareness all rely on the nervous system to produce a specific firing pattern in response to an either an efferent or afferent signal. Sports are governed by the same production and perception of oscillations that govern much of human activity. For example, in basketball, in order to anticipate the game one must recognize rhythmic patterns of other players and perform actions calibrated to these movements. "The rhythm of a game of basketball emerges from the rhythm of individuals, the rhythm among team members, and the rhythmic contrasts between opposing teams".
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The neurophysiological mechanisms by which phantom limbs occur is still under debate. A common theory posits that the afferent neurons, since deafferented due to amputation, typically remap to adjacent cortical regions within the brain. This can cause amputees to report feeling their missing limb being touched when a seemingly unrelated part of the body is stimulated (such as if the face is touched, but the amputee also feels their missing arm being stroked in a specific location). Another facet of phantom limbs is that the efferent copy (motor feedback) responsible for reporting on position to the body schema does not attenuate quickly.
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Collins is the scientific co- founder and currently chairs the Scientific Advisory Board (SAB) of Sample6 Technologies, Synlogic and EnBiotix. He serves on the Board of Directors of Fulcrum Therapeutics and the SAB of Agilis Biotherapeutics, Evelo Biosciences, enEvolv, Indigo Agriculture, Joule Unlimited, PureTech Health and Excel Medical Ventures. Additionally, he has served on the SAB of Mannkind Corporation, Seres Health, Codon Devices, Selventa, Gene Network Sciences, Epitome Biosystems, Afferent Corp, Cellicon Biotechnologies, Synereca Pharmaceuticals, LifeWave Ltd, and Bios Group Inc. Collins has also served as a science advisor to Unilever, Lifebuoy, Agilent, Momenta Pharmaceuticals, the New England Patriots, and Brooks Sports.
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At gestational weeks 19–23, PCD is observed in post-mitotic cells. The prevailing theory explaining this observation is the neurotrophic theory which states that PCD is required to optimize the connection between neurons and their afferent inputs and efferent targets. Another theory proposes that developmental PCD in the nervous system occurs in order to correct for errors in neurons that have migrated ectopically, innervated incorrect targets, or have axons that have gone awry during path finding. It is possible that PCD during the development of the nervous system serves different functions determined by the developmental stage, cell type, and even species.
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Shortly after a spinal nerve exits the intervertebral foramen, it branches into the dorsal ramus, the ventral ramus, and the ramus communicans. Each of these three structures carries both sensory and motor information. Each spinal nerve carries both sensory and motor information, via efferent and afferent nerve fibers - ultimately via the motor cortex in the parietal cortex - but also through the phenomenon of reflex. Spinal nerves are referred to as “mixed nerves.” In the thoracic region they remain distinct from each other and each innervates a narrow strip of muscle and skin along the sides, chest, ribs, and abdominal wall.
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All stimuli received by the receptors listed above are transduced to an action potential, which is carried along one or more afferent neurons towards a specific area of the brain. While the term sensory cortex is often used informally to refer to the somatosensory cortex, the term more accurately refers to the multiple areas of the brain at which senses are received to be processed. For the five traditional senses in humans, this includes the primary and secondary cortices of the different senses: the somatosensory cortex, the visual cortex, the auditory cortex, the primary olfactory cortex, and the gustatory cortex.Brynie, F.H. (2009).
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Angiotension converting enzyme The pathogenesis of renovascular hypertension involves the narrowing of the arteries supplying the kidneys which causes a low perfusion pressure that is detected by the juxtaglomerular apparatus (via the macula densa cells, which act as baroreceptors; located on the afferent arteriole wall). This leads to renin secretion that causes the angiotensinogen conversion to angiotensin I. Angiotensin I then proceeds to the lung where it is converted to angiotensin II via angiotensin converting enzyme (ACE). In most people fibromuscular dysplasia or atherosclerosis is the reason for the occlusion of a renal artery which ultimately leads to this condition.
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One area of the brain involved in reduction of pain sensation is the periaqueductal gray matter that surrounds the third ventricle and the cerebral aqueduct of the ventricular system. Stimulation of this area produces analgesia (but not total numbing) by activating descending pathways that directly and indirectly inhibit nociceptors in the laminae of the spinal cord. Descending pathways also activate opioid receptor-containing parts of the spinal cord. Afferent pathways interfere with each other constructively, so that the brain can control the degree of pain that is perceived, based on which pain stimuli are to be ignored to pursue potential gains.
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Based on thermodynamic principles, thermoclines can be determined to establish the spread of cooling from particular cooling surfaces. Therefore, for each cooling device with a known and consistent surface area, the temperature can be set at the same value for each trial or experiment to generate the same thermoclines and replicate the same volume of deactivation. Therefore, specifically selected regions of tissue can be reversibly deactivated in a controlled and reproducible way. 20°C has been found to be the critical temperature for active neuronal signals; below this temperature, afferent signals cannot activate neurons and the tissue is considered deactivated.
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The somatosensory system comprises a diverse range of receptors and processing centers to produce the perception of touch, temperature, proprioception, and nociception. Receptors are located throughout the body including the skin, epithelia, internal organs, skeletal muscles, bones, and joints. The cutaneous receptors of the skin project in an orderly fashion to the spinal cord, and from there, via different afferent pathways (dorsal column-medial lemniscus tract and spinothalamic tract), to the ventral posterior nucleus of the thalamus and the primary somatosensory cortex. Again, adjacent areas on the skin are represented by adjacent neurons in all aforementioned structures.
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The central axons on primary sensory neurons in the taste system in the cranial nerve ganglia connect to lateral and rostral regions of the nucleus of the solitary tract which is located in the medulla and is also known as the gustatory nucleus. The most pronounced gustatory nucleus is the rostral cap of the nucleus solitarius which is located at the ponto-medullary junction. Afferent taste fibers from the facial and from the facial and glossopharyngeal nerves are sent to the nucleus solitarius. The gustatory system then sends information to the thalamus which ultimately sends information to the cerebral cortex.
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In this context, the superficial region is considered to be 15-55μm deep into the SFO, and the "deep" region anything below that. From these reactions to certain hormones and other molecules, a model of the neuronal organization of the SFO is suggested in which angiotensin-sensitive neurons lying superficially are excited by substances borne by blood or cerebrospinal fluid, and synapse with deeper carbachol-sensitive neurons. The axons of these deep neurons pass out of the SFO in the columns and body of the fornix. Afferent fibers from the body and columns of the fornix polysynaptically excite both superficial and deep neurons.
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Various types of brain-body interactions have been distinguished. For example, brain-gut interactions are biochemical signaling that takes place between the gastrointestinal tract and the central nervous system. Brain-heart interactions link cardiac physiology to activity in the central and peripheral nervous system and may explain how peripheral cardiovascular arousal can influence decision making and the regulation of social and emotional behaviours. Brain-muscle interactions involve both efferent nerve fibres that transmit action potentials to the muscles to generate muscle contractions and afferent nerve fibres that transmit somatosensory information back to the central nervous system.
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The chemical structure of hydroxy- alpha sanshool is similar to that of capsaicin, but the mechanism of action by which it induces nerve sensations has been a matter of debate. Although the compound is an agonist at the pain integration channels TRPV1 and TRPA1 like capsaicin, newer evidence suggests that the tandem pore domain potassium channels KCNK3, KCNK9, and KCNK18 are primarily responsible for sanshool's effects. Hydroxy-alpha sanshool excites D-hair afferent nerve fibers, a distinct subset of the sensitive light touch receptors in the skin, and targets novel populations of Aβ and C-fiber nerve fibers.
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The insula is well-situated for the integration of information relating to bodily states into higher-order cognitive and emotional processes. The insula receives information from "homeostatic afferent" sensory pathways via the thalamus and sends output to a number of other limbic-related structures, such as the amygdala, the ventral striatum, and the orbitofrontal cortex, as well as to motor cortices. A study using magnetic resonance imaging found that the right anterior insula is significantly thicker in people that meditate. Other research into brain activity and meditation has shown an increase in grey matter in areas of the brain including the insular cortex.
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The medial reticular formation and lateral reticular formation are two columns of nuclei with ill-defined boundaries that send projections through the medulla and into the midbrain. The nuclei can be differentiated by function, cell type, and projections of efferent or afferent nerves. Moving caudally from the rostral midbrain, at the site of the rostral pons and the midbrain, the medial RF becomes less prominent, and the lateral RF becomes more prominent. Existing on the sides of the medial reticular formation is its lateral cousin, which is particularly pronounced in the rostral medulla and caudal pons.
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This acts on the kidneys to inhibit the secretion of renin and aldosterone causing the release of sodium, and accompanying water into the urine, thereby reducing the blood volume. This information is then conveyed, via afferent nerve fibers, to the solitary nucleus in the medulla oblongata. From here motor nerves belonging to the autonomic nervous system are stimulated to influence the activity of chiefly the heart and the smallest diameter arteries, called arterioles. The arterioles are the main resistance vessels in the arterial tree, and small changes in diameter cause large changes in the resistance to flow through them.
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Corrugator supercilii muscle Because facial expressions involve both motor (efferent) and sensory (afferent) mechanisms, it is possible that effects attributed to facial feedback are due solely to feedback mechanisms, or feed- forward mechanisms, or some combination of both. Recently, strong experimental support for a facial feedback mechanism is provided through the use of botulinum toxin (commonly known as Botox) to temporarily paralyze facial muscles. Botox selectively blocks muscle feedback by blocking presynaptic acetylcholine receptors at the neuromuscular junction. Thus, while motor efference commands to the facial muscles remain intact, sensory afference from extrafusal muscle fibers, and possibly intrafusal muscle fibers, is diminished.
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Resiniferatoxin has a score of 16 billion Scoville heat units, making pure resiniferatoxin about 500 to 1000 times hotter than pure capsaicin.National Institutes of Health, Clinical Center Department of Perioperative Medicine Chemical from cactus-like plant shows promise in controlling surgical pain, while leaving touch and coordination intact, rat study shows News release December 21, 2017, retrieved 28 February 2018. Resiniferatoxin activates transient vanilloid receptor 1 (TRPV1) in a subpopulation of primary afferent sensory neurons involved in nociception, the transmission of physiological pain. TRPV1 is an ion channel in the plasma membrane of sensory neurons and stimulation by resiniferatoxin causes this ion channel to become permeable to cations, especially calcium.
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In this case, the signal from the afferent fiber does not reach the brain, but produces the reflexive movement by direct connections with the efferent nerves in the spine. However, the majority of muscle activity is volitional, and the result of complex interactions between various areas of the brain. Nerves that control skeletal muscles in mammals correspond with neuron groups along the primary motor cortex of the brain's cerebral cortex. Commands are routed through the basal ganglia and are modified by input from the cerebellum before being relayed through the pyramidal tract to the spinal cord and from there to the motor end plate at the muscles.
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Gheorghe Marinescu and Anghel Radovici in their seminal 1920 paper hypothesized that both the afferent (receptive) and efferent (motor) arms of the reflex are on the same side (ipsilateral) to the hand stimulated; this hypothesis remains unsubstantiated. The PMR has been found to be present more frequently in various neurological conditions, both localized and diffuse. These include congenital conditions such as Down syndrome, where it is unclear whether the reflex persists throughout life, or disappears and then re-appears in association with the onset of Alzheimer disease pathology. The reflex is common in the elderly population and should not be taken as indicative of a dementing process.
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The substantia gelatinosa is one point (the nucleus proprius being the other) where first order neurons of the spinothalamic tract synapse. Many μ and κ-opioid receptors, presynaptic and postsynaptic, are found on these nerve cells; they can be targeted to manage pain of distal origin. For instance, neuraxial administration of opioids results in analgesia primarily by action in the dorsal horn of the spinal cord in the substantia gelatinosa where they inhibit release of excitatory neurotransmitters such as substance P and glutamate and inhibit afferent neural transmission to the brain from incoming peripheral pain neurons via hyperpolarization of postsynaptic neurons. C fibers terminate at this layer.
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The inhibition of calcineurin by cyclosporine and FK506 causes hypertension and hypertensive heart disease. Acutely, the neural mechanism is observed as the increase in blood pressure is accompanied by increased activity of efferent sympathetic nerve. The increased outflow of sympathetic efferents is a result of neural reflex due to the activation of renal and other subdiaphragmtic visceral afferents by calcineurin inhibitors. The fact that (1) the reflex activation of efferent sympathetic nerve activity and the increase in blood pressure by cyclosporine are attenuated in synapsin-deficient animal models and (2) synapsins are present in renal afferent/sensory nerve endings suggests that synapsins constitute putative substrates for calcineurin.
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The melanocortin system is a critical regulator of energy balance, in both feeding behaviors and energy expenditure, as well as peripheral tissues such as skin and hair. This system is a principal nexus of body weight regulation through its role in appetite and energy expenditure via leptin, ghrelin and agouti- related protein. It receives inputs from hormones, nutrients and afferent neural inputs, and is unique in its composition of fibers which express both agonists and antagonists of melanocortin receptors. Much of what is known about brain control's of overall energy balance and fat storage stem from the discoveries about the hypothalamic melanocortin system and leptin.
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Garraway then explored the descending serotonergic projections that modulate the DDH neurons. She used an in vitro slice preparation of DDH neurons and applied various serotonin receptor ligands to assess the effects of modulation at each serotonin receptor subtype in the primary afferent neurons. She found that the afferents are in fact modulated by several serotonin receptors and that 5-HT1A modulation facilitates evoked responses whereas 5-HT7 depressed evoked responses. Her work was one of the first identifications of the presence and effects of 5-HT7 receptors in the spinal cord and her results showed promise in using selective serotonin receptor targeting in the modulation of pain.
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The enzyme renin is secreted by pericytes (mural cells) (1) in the vicinity of the afferent arterioles and similar microvessels of the kidney from specialized cells of the juxtaglomerular apparatus—the juxtaglomerular cells, in response to three stimuli: # A decrease in arterial blood pressure (that could be related to a decrease in blood volume) as detected by baroreceptors (pressure-sensitive cells). This is the most direct causal link between blood pressure and renin secretion (the other two methods operate via longer pathways). # A decrease in sodium load delivered to the distal tubule. This load is measured by the macula densa of the juxtaglomerular apparatus.
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What is described above concerned the input map or "inmap" (corresponding to the spatial distribution of the afferent axons from one source to one target). This does not correspond necessarily to the output map or outmap (corresponding to the distribution of the neurons in relation to their axonal targets). Physiological studies and transsynaptic viral markers have shown that islands of pallidal neurons (only their cell bodies or somata, or trigger points) sending their axons through their particular thalamic territories (or nuclei) to one determined cortical target are organized into radial bands.Hoover and Strick 1994Middleton and Strick, 1994 These were assested to be totally representative of the pallidal organisation.
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One study taught amputees over a two-week period to identify different patterns of electrical stimuli being applied to their stump to help reduce their PLP. It was found that the training reduced PLP in the patients and reversed the cortical reorganization that had previously occurred. However, a recent study by Tamar R. Makin suggests that instead of PLP being caused by maladaptive plasticity, it may actually be pain induced. The maladaptive plasticity hypothesis suggests that once afferent input is lost from an amputation, cortical areas bordering the same amputation area will begin to invade and take over the area, affecting the primary sensorimotor cortex, seeming to cause PLP.
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For this reason, in both the switch and hybrid movements, the path of the moving limb is smooth and uninterrupted. Studies from EMG recordings have indicated that reciprocal inhibition between hip-related interneurons in the CPG for the scratch reflex is not necessary for the production and maintenance of the hip-flexor rhythm that is a key part of the scratch reflex. This research further supports the findings on switch and hybrid movements, which suggest a modular organization of unit generator CPGs used in combination to achieve a task. Another general aspect of the scratch response is that the response continues even after afferent input from the stimulated zone ceases.
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Extraglomerular mesangial cells (also known as Lacis cells, Polkissen cells, or Goormaghtigh cells) are light-staining pericytes in the kidney found outside the glomerulus, near the vascular pole. They resemble smooth muscle cells and play a role in renal autoregulation of blood flow to the kidney and regulation of systemic blood pressure through the renin–angiotensin system. Extraglomerular mesangial cells are part of the juxtaglomerular apparatus, along with the macula densa cells of the distal convoluted tubule and the juxtaglomerular cells of the afferent arteriole. The specific function of extraglomerular mesangial cells is not well understood, although it has been associated with the secretion of erythropoietin and secretion of renin.
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The fetus, which develops within a fluid-filled amniotic sac, relies on the placenta for respiratory gas exchange rather than the lungs. While not involved in fetal oxygenation, fetal breathing movements (FBM) nevertheless have an important role in lung growth and in development of respiratory muscles and neural regulation. FBM are regulated differently in many respects than postnatal respiration, which results from the unique intrauterine environment. At birth, the transition to continuous postnatal respiration involves a fall in temperature, gaseous distention of the lungs, activation of the Hering-Breuer reflex, and functional connectivity of afferent O2 chemoreceptor activity with respiratory motoneurons and arousal centers.
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In the auditory system of bats, like in auditory systems of other vertebrates, primary sensory afferent neurons, which receive inputs from hair cells from a restricted region of the organ of Corti in the cochlea, are the simple feature detectors. These structures are sensitive to a restricted range of frequencies and therefore function as tuned filters. Experimentally, Nobuo Suga and his colleagues (1990) noted that various constant frequency (CF) and frequency modulated (FM) harmonics excited different parts of the basilar membrane because of the frequency difference in the call. Auditory nerve fibers take this slightly-processed sensory information to the cochlear nucleus where information either converges or diverges into parallel pathways.
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The posterior grey column, also known as the posterior (or dorsal) horn of spinal cord, is divided into several laminae, based on the type of sensory information sent to each section. Laminae I and II are sent information from afferent neurons that sense nociception, temperature, and itching, laminae III and IV are sent information from neurons that sense mechanical pressure, and laminae V and VI are sent information from proprioceptors. It is known to be the primary relay point for haptic and nociceptive messages. The posterior horn is also known as a partially layered structure because only laminae I and II are well defined.
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The vertebrate nervous system is divided into the central and peripheral nervous systems. The central nervous system (CNS) consists of the brain, retina, and spinal cord, while the peripheral nervous system (PNS) is made up of all the nerves and ganglia (packets of peripheral neurons) outside of the CNS that connect it to the rest of the body. The PNS is further subdivided into the somatic and autonomic nervous systems. The somatic nervous system is made up of "afferent" neurons, which bring sensory information from the somatic (body) sense organs to the CNS, and "efferent" neurons, which carry motor instructions out to the voluntary muscles of the body.
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Structures such as the corona radiata, occipital-frontal fasciculus and uncinate fasciculus project to the claustrum from frontal, pericentral, parietal and occipital regions. Reciprocal connections also exist with motor, somatosensory, auditory and visual cortical regions. Altogether, these findings leave the claustrum as the most highly connected structure per regional volume in the brain and suggest that it may serve as a hub to coordinate activity of cerebral circuits. Interestingly, even with this extensive connectivity, most projections to and from the claustrum are ipsilateral (although there are still contralateral projections), and little evidence exists to describe its afferent or efferent connections with the brainstem and spinal cord.
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Using acoustic stimuli to activate the MOC reflex pathway, recordings have been made from single efferent fibres in guinea pigs and cats. Both studies confirmed that MOC neurons are sharply tuned to frequency, as previously suggested by Cody and Johnstone (1982), and Robertson (1984). They also showed that the firing rate of MOC neurons increased as the intensity of sound increased from 0 to 100 dB SPL, and have comparable thresholds (within ~15 dB) to afferent neurons. Furthermore, both studies showed that most MOC neurons responded to sound presented in the ipsilateral ear, consistent with the majority of mammalian MOC neurons being contralaterally located.
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It begins a few hours after capsaicin application and may last even several weeks. The reversible desensitization was found useful in the treatment of pain, whereas the site- specific ablation of sensory nerves transmitting pain stimuli is a promising approach (‘molecular scalpel’) to achieve a permanent pain relief in patients suffering from bone cancer pain or HIV-induced neuropathies. Desensitization and depletion of pronociceptive neurotransmitters induce chemical denervation with a loss of function, which is clinically used in osteoarthritis, diabetic neuropathy, psoriasis and others. In dorsal root ganglia and the sciatic nerve, zucapsaicin decreases levels of SP and CGRP, indicating that it influences peptidergic afferent neurons via a desensitization mechanism[41].
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The Golgi tendon reflex operates as a protective feedback mechanism to control the tension of an active muscle by causing relaxation before the tendon tension becomes high enough to cause damage. First, as a load is placed on the muscle, the afferent neuron from the Golgi tendon organ fires into the central nervous system. Second, the motor neuron from the spinal cord is inhibited via an IPSP and muscle relaxes. Because the Ib inhibitory interneurons receive convergent descending pathways and multisensory inputsincluding cutaneous receptors, muscle spindles, and joint receptors, they can provide better protection, such as when the joint receptors are signaling joint hyperextension or hyperflexion.
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Afferent neurons significant in dyspnea arise from a large number of sources including the carotid bodies, medulla, lungs, and chest wall. Chemoreceptors in the carotid bodies and medulla supply information regarding the blood gas levels of O2, CO2 and H+. In the lungs, juxtacapillary (J) receptors are sensitive to pulmonary interstitial edema, while stretch receptors signal bronchoconstriction. Muscle spindles in the chest wall signal the stretch and tension of the respiratory muscles. Thus, poor ventilation leading to hypercapnia, left heart failure leading to interstitial edema (impairing gas exchange), asthma causing bronchoconstriction (limiting airflow) and muscle fatigue leading to ineffective respiratory muscle action could all contribute to a feeling of dyspnea.
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The pathophysiology of GvHD includes three phases: # The afferent phase: activation of APC (antigen presenting cells) # The efferent phase: activation, proliferation, differentiation and migration of effector cells # The effector phase: target tissue destruction Activation of APC occurs in the first stage of GvHD. Prior to haematopoietic stem cell transplantation, radiation or chemotherapy results in damage and activation of host tissues, especially intestinal mucosa. This allows the microbial products to enter and stimulate pro-inflammatory cytokines such as IL-1 and TNF-α. These proinflammatory cytokines increase the expression of MHC and adhesion molecules on APCs, thereby increasing the ability of APC to present antigen.
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Next, the superior longitudinal muscle elevates the apex of the tongue to make contact with the hard palate and the bolus is propelled to the posterior portion of the oral cavity. Once the bolus reaches the palatoglossal arch of the oropharynx, the pharyngeal phase, which is reflex and involuntary, then begins. Receptors initiating this reflex are proprioceptive (afferent limb of reflex is IX and efferent limb is the pharyngeal plexus- IX and X). They are scattered over the base of the tongue, the palatoglossal and palatopharyngeal arches, the tonsillar fossa, uvula and posterior pharyngeal wall. Stimuli from the receptors of this phase then provoke the pharyngeal phase.
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Enactive interfaces are new types of human-computer interface that express and transmit the enactive knowledge by integrating different sensory aspects. The driving concept of enactive interfaces is then the fundamental role of motor action for storing and acquiring knowledge (action driven interfaces). Enactive interfaces are then capable of conveying and understanding gestures of the user, in order to provide an adequate response in perceptual terms. Enactive interfaces can be considered a new step in the development of the human-computer interaction because they are characterized by a closed loop between the natural gestures of the user (efferent component of the system) and the perceptual modalities activated (afferent component).
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Schematic depicting how the RAAS works. Here, activation of the RAAS is initiated by a low perfusion pressure in the juxtaglomerular apparatus Macula densa cells sense changes in sodium chloride level, and will trigger an autoregulatory response to increase or decrease reabsorption of ions and water to the blood (as needed) in order to alter blood volume and return blood pressure to normal. A decrease in afferent arteriole diameter causes a decrease in the GFR (glomerular filtration rate), resulting in a decreased concentration of sodium and chloride ions in the filtrate and/or decreased filtrate flow rate. Reduced blood pressure means decreased venous pressure and, hence, a decreased peritubular capillary pressure.
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The white rami communicantes are the preganglionic sympathetic outflow from the spinal cord. The cell bodies for the preganglionic sympathetic myelinated fibers in the white rami communicantes lie in the ipsilateral (same sided) intermediolateral cell column in the spinal cord which extends from T1-L2. These rami also contain general visceral afferent fibers (sensory from the organs) whose primary cell bodies reside dorsal root ganglia (which then synapse in the dorsal horn). The preganglionic sympathetic fibers will enter into the sympathetic trunk and either synapse at the ganglion on the same level, or travel up or down the sympathetic trunk to arrive at the correct spinal level for their action.
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The anal wink, anal reflex, perineal reflex, or anocutaneous reflex is the reflexive contraction of the external anal sphincter upon stroking of the skin around the anus. A noxious or tactile stimulus will cause a wink contraction of the anal sphincter muscles and also flexion. The stimulus is detected by the nociceptors in the perineal skin to the pudendal nerve, where a response is integrated by the spinal cord sacral segments S2-S4. The absence of this reflex indicates that there is an interruption of the reflex arc, or damage to the spinal cord, which may be in the sensory afferent limb or the motor efferent limb.
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Vestibular duct perilymph vibrations bend organ of Corti outer cells (4 lines) causing prestin to be released in cell tips. This causes the cells to be chemically elongated and shrunk (somatic motor), and hair bundles to shift which, in turn, electrically affects the basilar membrane’s movement (hair-bundle motor). These motors (outer hair cells) amplify the traveling wave amplitudes over 40-fold. The outer hair cells (OHC) are minimally innervated by spiral ganglion in slow (unmyelinated) reciprocal communicative bundles (30+ hairs per nerve fiber); this contrasts inner hair cells (IHC) that have only afferent innervation (30+ nerve fibers per one hair) but are heavily connected.
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An efferent lymph vessel may directly drain into one of the (right or thoracic) lymph ducts, or may empty into another lymph node as its afferent lymph vessel. Both the lymph ducts return the lymph to the blood stream by emptying into the subclavian veins The functional unit of a lymph vessel is known as a lymphangion, which is the segment between two semilunar valves. Since it is contractile, depending upon the ratio of its length to its radius, it can act either like a contractile chamber propelling the fluid ahead, or as a resistance vessel tending to stop the lymph in its place.
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The projection fibers consist of efferent and afferent fibers uniting the cortex with the lower parts of the brain and with the spinal cord. In human neuroanatomy, bundles of axons (nerve fibers) called tracts, within the brain, can be categorized by their function into association fibers, projection fibers, and commissural fibers. In the neocortex, projection neurons are excitatory neurons that send axons to distant brain targets. Considering the six histologically-distinct layers of the neocortex, associative projection neurons extend axons within one cortical hemisphere; commissural projection neurons extend axons across the midline to the contralateral hemisphere; and corticofugal projection neurons extend axons away from cortex.
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Under normal conditions, pain conduction begins with some noxious signal followed by an action potential carried by nociceptive (pain sensing) afferent neurons, which elicit excitatory postsynaptic potentials (EPSP) in the dorsal horn of the spinal cord. That message is then relayed to the cerebral cortex, where we translate those EPSPs into "pain." Since the discovery of astrocyte-neuron signaling, our understanding of the conduction of pain has been dramatically complicated. Pain processing is no longer seen as a repetitive relay of signals from body to brain, but as a complex system that can be up- and down-regulated by a number of different factors.
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The axon reflex results in a localized response to only the locally innervated cells of the single neuron where the signal originated. The axon reflex pathway does not include an integration center or synapse that relays communication between neurons in the spinal cord reflex. The stimulus, therefore, is diverted to the effector organ without entering the neuronal cell body and therefore indicates that the axon reflex is not a true reflex where afferent impulses pass through the central nervous system before stimulating efferent neurons. The axon reflex was discovered and was described as "a new type of peripheral reflex" that bypasses the integration center and synapse in the central nervous system.
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Matrix cells of the thalamus, or calbindin- immuno-reactive neurons (CIR neurons), are widely distributed and diffusely dispersed in each of the nuclei of the dorsal thalamus. In comparison, parvalbumin immuno-reactive neurons (PIR neurons) can be found only in principal sensory and motor relay nuclei, and in the pulvinar nuclei as well as the intralaminar nuclei. The PIR neurons cluster together creating "densely terminating afferent fibers…forming a core imposed on a diffuse background matrix of PIR cells" (Jones 2001). PIR cells tend to project upon the cerebral cortex and terminate in an organized topographic manner in specifically localized zones (in deep layer III and in the middle layer IV).
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These three layers are composed of pyramidal cells, cells that have a pyramidal shaped axon with long dendrites connecting to other cells in neighbouring columns. The second section of the neomammalian brain is the Internal Granular Layer, and is known as layer four by neuroscientists; this layer is responsible for receiving afferent signals from the hypothalamus and sends messages to the other layers. For example, layer four would receive messages about external temperature changes. The Internal Granular Layer acts as a medium which receives, processes and the sends signals to other parts of the brain, allowing the body to respond in such a way to combat the change in environment.
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Form and colour would be derived at a subsequent stage, not as the result of an isomorphic filling-in process, but as an attribute of an object or proto- object. This theory is called the symbolic filling-in theory. According to the isomorphic filling-in theory, colour is represented by the activity of cells whose receptive fields point at the surface, but it is assumed that these cells receive additional activation through horizontal connections that keeps their activity level high despite mechanisms of lateral inhibition tending to suppress surface activity and despite the transient nature of the afferent signals. The lateral activation comes from receptive fields at contrast borders.
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Unlike the topographic maps of the senses, the neurons of the motor cortex are efferent neurons that exit the brain instead of bringing information to the brain through afferent connections. The motor system is responsible for initiating voluntary or planned movements (reflexes are mediated at the spinal cord level, so movements that associated with a reflex are not initiated by the motor cortex). The activation from the motor cortex travels through Betz cells down the corticospinal tract through upper motor neurons, terminating at the anterior horn of the grey matter where lower motor neurons transmit the signal to peripheral motor neurons and, finally, the voluntary muscles.
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The impact of disrupted temporal coding on human auditory perception has been explored using physiologically inspired signal-processing tools. The reduction in neural synchrony has been simulated by jittering the phases of the multiple frequency components in speech, although this has undesired effects in the spectral domain. The loss of auditory nerve fibers or synapses has been simulated by assuming (i) that each afferent fiber operates as a stochastic sampler of the sound waveform, with greater probability of firing for higher-intensity and sustained sound features than for lower-intensity or transient features, and (ii) that deafferentation can be modeled by reducing the number of samplers. However, this also has undesired effects in the spectral domain.
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Through electrophysiological studies and neuronal tracing, these characteristics do not fully support the typical person with central facial palsy. Often, transcranial magnetic stimulation (TMS) is used to understand the bilateral corticonuclear projections of the lower facial motor neurons. This idea using bilateral innervation to the upper facial motor neurons is rarely tested by humans because of the afferent fibers in the trigeminal nerve are distributed over the head and face and could cause damage. Supranuclear motor innervation of the facial musculature is difficult to examine because the circuitry is quite complex, only a few cases are described in literature of central facial palsy and the absence of bilateral perioral muscle responses after TMS of the affected hemisphere.
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In vertebrates, the cerebellar vermis develops between two bilaterally symmetrical formations located dorsal to the upper end of the medulla oblongata, or rhombencephalon. This is the region of termination for the fibers of the vestibular nerve and lateral line nerves; thus, these are the oldest afferent paths to the cerebellum and cerebellar vermis. In bony fish, or teleosts, it has been proposed that the cerebellar auricles, which receive a large amount of input from the vestibulolateral line system, constitute the vestibulocerebellum and are homologues of the flocculonodular lobe of higher vertebrates along with the corpus cerebelli, which receives spinocerebellar and tectocerebellar fibers. The labyrinth and the lateral line organs of lampreys have structural and functional similarity.
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At around the same time, Moritz Heinrich Romberg, a Berlin neurologist, was describing unsteadiness made worse by eye closure or darkness, now known as the eponymous Romberg's sign, once synonymous with tabes dorsalis, that became recognised as common to all proprioceptive disorders of the legs. Later, in 1880, Henry Charlton Bastian suggested "kinaesthesia" instead of "muscle sense" on the basis that some of the afferent information (back to the brain) comes from other structures, including tendons, joints, and skin. In 1889, Alfred Goldscheider suggested a classification of kinaesthesia into three types: muscle, tendon, and articular sensitivity. In 1906, Charles Scott Sherrington published a landmark work that introduced the terms "proprioception", "interoception", and "exteroception".
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Infiltration from the subarachnoid space into the spinal cord occurs primarily along the perivascular tissues that surround blood vessels at the brain entrance. Infiltration from the anterior median fissure, a 3mm deep furrow on the anterior side of the spinal cord, to the anterior horn of the spinal cord, the ventral grey matter of the spinal cord, is found along the central artery. Direct infiltration of the nerve roots is also observed, mostly from the dorsal roots (the afferent sensory root of the spinal nerve) than the ventral roots (the efferent motor root of a spinal nerve). With mild infiltration, tumor cells are found diffusely in the subarachnoid space from the cervical to sacral levels.
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Ventilatory rate (respiratory minute volume) is tightly controlled and determined primarily by blood levels of carbon dioxide as determined by metabolic rate. Blood levels of oxygen become important in hypoxia. These levels are sensed by central chemoreceptors on the surface of the medulla oblongata for increased pH (indirectly from the increase in CSF of carbon dioxide), and the peripheral chemoreceptors in the arterial blood for oxygen and carbon dioxide. Afferent neurons from the peripheral chemoreceptors are via the glossopharyngeal nerve (CN IX) and the vagus nerve (CN X). Levels of CO2 rise in the blood when the metabolic use of O2, and the production of CO2 is increased during, for example, exercise.
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In neuroanatomy, habenula (diminutive of Latin habena meaning rein) originally denoted the stalk of the pineal gland (pineal habenula; pedunculus of pineal body), but gradually came to refer to a neighboring group of nerve cells with which the pineal gland was believed to be associated, the habenular nucleus. The habenular nucleus is a set of well-conserved structures in all vertebrate animals. Currently, this term refers to this separate cell mass in the caudal portion of the dorsal diencephalon, known as the epithalamus, found in all vertebrates on both sides of the third ventricle. It is embedded in the posterior end of the stria medullaris from which it receives most of its afferent fibers.
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This is an inhibitory postsynaptic potential (IPSP), as it changes the charge across the membrane to be further from the firing threshold. Neurotransmitters are not inherently excitatory or inhibitory: different receptors for the same neurotransmitter may open different types of ion channels. EPSPs and IPSPs are transient changes in the membrane potential, and EPSPs resulting from transmitter release at a single synapse are generally far too small to trigger a spike in the postsynaptic neuron. However, a neuron may receive synaptic inputs from hundreds, if not thousands, of other neurons, with varying amounts of simultaneous input, so the combined activity of afferent neurons can cause large fluctuations in membrane potential or subthreshold membrane potential oscillations.
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Initially, iodoresiniferatoxin was thought to be a competitive antagonist of the TRPV1 receptor with high affinity (Kd = 4.3 ± 0.9 nM to HEK 293/VR1 and Kd = 4.2 ± 1.0 nM to rat spinal cord membranes), but recent research indicated also partial transient agonistic characteristics in the thermoregulatory system in mice, especially in higher concentrations ranging from 1 to 30 μM. The TRPV1 receptor encodes a protein of 838 amino acids forming a calcium-permeable channel that is activated by capsaicin but also by noxious heat and low extracellular pH. TRPV1 receptors are expressed in many systems in the central and peripheral nervous system, and have a particularly important role in signal conduction in afferent pain pathways.
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Head thought it probable that sensation related to innervation of the skin, but there was no accurate knowledge of cutaneous distribution of afferent fibres which enter the spinal cord by each dorsal root and terminate in one spinal segment. To remedy this lack of understanding, Head chose to investigate the anatomic distribution of cutaneous disturbances caused by herpes zoster. A careful study with A.W. Campbell enabled him to demonstrate the zones of skin affected by disease and from this he could chart the cutaneous distribution of different fibres originating from cells of each ganglion and reaching the corresponding segment of the spinal cord. From these investigations, Head and Campbell made two important discoveries.
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Zucapsaicin mediates an antinociceptive action via acting as an agonist at TRPV1. TRPV1 play an important physiological role of transducing chemical, mechanical and thermal stimuli as well as pain transduction, and participate in pain modulation and perception. They are mainly distributed in C sensory nerve fibers as well as Aẟ fibers to transmit sensory information involving inflammatory and neuropathic pain, and activation of these channels releasesomatostatin, calcitonin gene-related peptide (CGRP) and other neuropeptides (neurokinin A, kassinin), leading to neurogenic inflammation [A19720]. Zucapsaicin is also reported to affect the peptidergic afferent neurons via a desensitization mechanism to decrease the levels of dorsal root ganglia and sciatic calcitonin gene-related peptide (CGRP) and substance P (SP) [L877].
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Upper motor neuron lesions which damage the descending pathways down to the spinal cord may cause increase in muscle tone, partly because alpha motoneurons respond more to muscle spindle afferent inputs. This causes increased resistance to passive movement (that the patient doesn't initiate), called spasticity, which is associated with another neurological sign, the clasp-knife response, in which the spastic muscle initially resists passive movement strongly, and then suddenly yieldslike the motion of a pocketknife. The increased initial resistance comes from the stretch reflex hyperactivity, and the sudden collapse may involve the Golgi tendon reflex. The response is also known as the lengthening reaction because of the spastic muscle's reaction to lengthening.
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Romanians are also an ethnic minority in several nearby countries situated in Central, respectively Eastern Europe, particularly in Hungary, Czech Republic, Ukraine (including Moldovans), Serbia, and Bulgaria. Today, estimates of the number of Romanian people worldwide vary from 26 to 30 million according to various sources, evidently depending on the definition of the term 'Romanian', Romanians native to Romania and Republic of Moldova and their afferent diasporas, native speakers of Romanian, as well as other Balkan Romance-speaking groups considered by most scholars and the Romanian Academy as a constituent part of the broader Romanian people, specifically Aromanians, Megleno-Romanians, Istro-Romanians, and Vlachs of Serbia (including medieval Vlachs), in Croatia, in Bulgaria, or in Bosnia and Herzegovina.
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A motor signal from the central nervous system (CNS) to the periphery is called an efference, and a copy of this signal is called an efference copy. Sensory information coming from sensory receptors in the peripheral nervous system to the central nervous system is called afference. On a similar basis, nerves into the nervous system are afferent nerves and ones out are termed efferent nerves. When an efferent signal is produced and sent to the motor system, it has been suggested that a copy of the signal, known as an efference copy, is created so that exafference (sensory signals generated from external stimuli in the environment) can be distinguished from reafference (sensory signals resulting from an animal's own actions).
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Based on their functional relevance, the SFO neurons can be branded as either GE, featuring nonselective cation channels, or GI, featuring potassium channels. While the afferent projections of the SFO are considered less important than the various efferent connections, it is still notable that the subfornical organ receives synaptic input from the zona incerta and arcuate nucleus. Study of subfornical organ anatomy is still ongoing but evidence has demonstrated slow blood transit time which may facilitate the sensory capability of SFO, enabling increased contact time for blood-borne signals to penetrate its permeable capillaries and influence regulation of blood pressure and body fluids. This observation coincides with the fact that SFO neurons have been shown to be intrinsically osmosensitive.
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Lymph capillaries are slightly larger than their counterpart capillaries of the vascular system. Lymph vessels that carry lymph to a lymph node are called afferent lymph vessels, and those that carry it from a lymph node are called efferent lymph vessels, from where the lymph may travel to another lymph node, may be returned to a vein, or may travel to a larger lymph duct. Lymph ducts drain the lymph into one of the subclavian veins and thus return it to general circulation. Generally, lymph flows away from the tissues to lymph nodes and eventually to either the right lymphatic duct or the largest lymph vessel in the body, the thoracic duct.
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As a result of such decussations, the efferent connections of the cerebrum to the basal ganglia, the cerebellum and the spine are crossed, and the afferent connections from the spine, the cerebellum and the pons to the thalamus are crossed. As a result, motor, somatosensory, auditory, and visual primary regions in the forebrain represent predominantly the contralateral side of the body. Two of the cranial nerves show chiasmas: the chiasm of the optic tract (cranial nerve II) which originates from the eyes and inserts on the optic tectum of the midbrain, and the trochlear nerve (nerve IV) which originates in the ventral midbrain and innervates one of the six muscles that rotate the eye (superior oblique muscle).
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Its function is modulatory on signals going through thalamus (and the reticular nucleus). The thalamic reticular nucleus receives massive projections from the external segment of the Globus Pallidus, thought to play a part in disinhibition of thalamic cells, which is essential for initiation of movement (Parent and Hazrati, 1995) It has been suggested that the reticular nucleus receives afferent input from the reticular formation and in turn projects to the other thalamic nuclei, regulating the flow of information through these to the cortex. There is debate over the presence of distinct sectors within the nucleus that each correspond to a different sensory or cognitive modality. For original connectivity anatomy see Jones 1975.
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Flow chart depicting a detailed list of the political parties active in Romania since 1990, along with their afferent secessions and fusions/mergers. The 1992 local, legislative, and presidential elections indicated a political rift between the urban centres and the countryside. Rural voters, grateful for the restoration of most agricultural land to farmers but fearful of change, strongly favored President Iliescu and the FDSN; the urban electorate favored the CDR (a coalition of several parties – the strongest of which were the PNŢCD and the PNL – and civic organizations) and quicker reform. Iliescu easily won re-election from a field of five other candidates, and the FDSN won a plurality in both chambers of parliament.
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Zucapsaicin mediates an antinociceptive action via acting as an agonist at TRPV1. TRPV1 play an important physiological role of transducing chemical, mechanical and thermal stimuli as well as pain transduction, and participate in pain modulation and perception. They are mainly distributed in C sensory nerve fibers as well as Aẟ fibers to transmit sensory information involving inflammatory and neuropathic pain, and activation of these channels releasesomatostatin, calcitonin gene-related peptide (CGRP) and other neuropeptides (neurokinin A, kassinin), leading to neurogenic inflammation. Zucapsaicin is also reported to affect the peptidergic afferent neurons via a desensitization mechanism to decrease the levels of dorsal root ganglia and sciatic calcitonin gene-related peptide (CGRP) and substance P (SP).
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When a muscle is stretched, primary type Ia sensory fibers of the muscle spindle respond to both changes in muscle length and velocity and transmit this activity to the spinal cord in the form of changes in the rate of action potentials. Likewise, secondary type II sensory fibers respond to muscle length changes (but with a smaller velocity-sensitive component) and transmit this signal to the spinal cord. The Ia afferent signals are transmitted monosynaptically to many alpha motor neurons of the receptor-bearing muscle. The reflexly evoked activity in the alpha motoneurons is then transmitted via their efferent axons to the extrafusal fibers of the muscle, which generate force and thereby resist the stretch.
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When you experience a negative feeling, such as pain from a bump or an itch from a bug bite, a common reaction is an attempt to eliminate the feeling by rubbing the painful bump or scratching the itchy bite. These are examples of the gate control theory of pain that most can relate to. Gate control theory asserts that activation of nerves which do not transmit pain signals, called nonnociceptive fibers, can interfere with signals from pain fibers, thereby inhibiting pain. It is proposed that both small-diameter (pain-transmitting) and large-diameter (touch-, pressure-, and vibration- transmitting) afferent nerve fibers carry information from the site of the injury to two destinations in the dorsal horn: 1.
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A lightning bolt signifies increased neuron activation, while a crossed-out bolt signifies weakened or reduced activation. Aβ fibers activates the inhibitory interneuron, reducing the chances that the projection neuron will fire, even in the presence of a firing nociceptive fiber. Gate control theory asserts that activation of nerves which do not transmit pain signals, called nonnociceptive fibers, can interfere with signals from pain fibers, thereby inhibiting pain. Afferent pain-receptive nerves, those that bring signals to the brain, comprise at least two kinds of fibers - a fast, relatively thick, myelinated "Aδ" fiber that carries messages quickly with intense pain, and a small, unmyelinated, slow "C" fiber that carries the longer-term throbbing and chronic pain.
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The apical faces of the receptor cells have a small surface area with a high concentration of voltage dependent calcium channels and calcium activated potassium channels. Because the canal wall has a very high resistance, all of the voltage difference between the pore of the canal and the ampulla is dropped across the receptor epithelium which is about 50 microns thick. Because the basal membranes of the receptor cells have a lower resistance, most of the voltage is dropped across the apical faces which are excitable and are poised at threshold. Inward calcium current across the receptor cells depolarizes the basal faces causing presynaptic calcium release and release of excitatory transmitter onto the afferent nerve fibers.
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Thus, the TAL is an important segment of the TGF system, and its transport properties allow it to act as a key operator of the TGF system. A reduction of GFR occurs as a result of TGF when NaCl concentration at the sensor site is increased within the physiological range of approximately 10 to 60 mM. The TGF mechanism is a negative feedback loop in which the chloride ion concentration is sensed downstream in the nephron by the macula densa (MD), cells in the tubular wall near the end of TAL and the glomerulus. The muscle tension in the afferent arteriole is modified based on the difference between the sensed concentration and a target concentration.
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Peripheral nervous system box diagram The classification of peripheral nerves in the peripheral nervous system (PNS) groups the nerves into two main groups, the somatic and the autonomic nervous systems. Together, these two systems provide information regarding the location and status of the limbs, organs, and the remainder of the body to the central nervous system (CNS) via nerves and ganglia present outside of the spinal cord and brain. The somatic nervous system directs all voluntary movements of the skeletal muscles, and can be sub-divided into afferent and efferent neuronal flow. The autonomic nervous system is divided primarily into the sympathetic and parasympathetic nervous systems with a third system, the enteric nervous system, receiving less recognition.
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Naltalimide (INN) (code name TRK-130, formerly TAK 363) is a novel, centrally- acting opioid drug which is under development by Takeda and Toray for the treatment of overactive bladder/urinary incontinence. It acts as a potent and selective partial agonist of the μ-opioid receptor (Ki = 0.268 nM, EC50 = 2.39 nM, Emax = 66.1%) over the δ-opioid (Ki = 121 nM, EC50 = 26.1 nM, Emax = 71.0%) and κ-opioid receptors (Ki = 8.97 nM, EC50 = 9.51 nM, Emax = 62.6%). Notably, naltalimide somehow appears to lack certain undesirable side effects such as constipation seen with other μ-opioid receptor agonists such as morphine. It enhances bladder storage via suppression of the afferent limb of the micturition reflex pathway.
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However, vibrissae are different from other hair structures because they grow from a special hair follicle incorporating a capsule of blood called a blood sinus which is heavily innervated by sensory nerves. The mystacial macrovibrissae are shared by a large group of land and marine mammals (see images), and it is this group that has received by far the most scientific study. The arrangement of these whiskers is not random: they form an ordered grid of arcs (columns) and rows, with shorter whiskers at the front and longer whiskers at the rear (see images). In the mouse, gerbil, hamster, rat, guinea pig, rabbit, and cat, each individual follicle is innervated by 100–200 primary afferent nerve cells.
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The physiological type occurs before 28 weeks after conception and tend to last five to ten minutes. These hiccups are part of fetal development and are associated with the myelination of the phrenic nerve, which primarily controls the thoracic diaphragm. The phylogeny hypothesis explains how the hiccup reflex might have evolved, and if there is not an explanation, it may explain hiccups as an evolutionary remnant, held-over from our amphibious ancestors. This hypothesis has been questioned because of the existence of the afferent loop of the reflex, the fact that it does not explain the reason for glottic closure, and because the very short contraction of the hiccup is unlikely to have a significant strengthening effect on the slow-twitch muscles of respiration.
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The papilla is shaped like a truncated cone, the smaller end being directed downward and attached to the tongue, the broader part or base projecting a little above the surface of the tongue and being studded with numerous small secondary papillae and covered by stratified squamous epithelium. Ducts of lingual salivary glands, known as Von Ebner's glands empty a serous secretion into the base of the circular depression, which acts like a moat. The function of the secretion is presumed to flush materials from the base of circular depression to ensure that taste buds can respond to changing stimuli rapidly. The circumvallate papillae get special afferent taste innervation from cranial nerve IX, the glossopharyngeal nerve, even though they are anterior to the sulcus terminalis.
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As such, various properties of F-wave motor nerve conduction are analyzed in nerve conduction studies (NCS), and often used to assess polyneuropathies, resulting from states of neuronal demyelination and loss of peripheral axonal integrity. With respect to its nomenclature, the F-wave is so named as it was initially studied in the smaller muscles of the foot. The observation of F-waves in the same motor units (MU) as those present in the direct motor response (M), along with the presence of F-waves in deafferented animal and human models, indicates that F-waves require direct activation of motor axons to be elicited, and do not involve conduction along afferent sensory nerves. Thus, the F-wave is considered a wave, as opposed to a reflex.
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Spinothalamic tract (STT) cells that project from laminae I and V in the lumbrosacral area of the spinal cord project to the VPL in the VB. STT cells located in the cervical area of the spinal cord are the densest and project from the neck of the dorsal horn to the VPL of the VB. Most projections to the VB are contralateral while only a few projections to the VB are ipsilateral. Excitatory inputs to the VB are medial lemniscal (ML) and corticothalamic (CT) glutamatergic synapses. The ML is a sensory afferent input and the CT is from layer VI of the primary sensory cortex. The VB also gets inputs from areas in the brain stem which release acetylcholine (ACh) that can modulate activity in the VB.
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While conducting research into the (afferent) sensory nervous system with evoked potentials, Sgro also began to investigate devices and techniques to determine the state of the (efferent) motor nervous system using TMS with the goal of more effective detection of sub-clinical diseases and increased sensitivity of the motor system during intra-operative patient monitoring. Sgro and his associates studied the theoretical and practical issues involved in the design of a high magnetic field strength and rapid transcranial magnetic stimulator which could exceed the historical safety limit of electrical brain stimulation (40 uC/cm2/phase at a stimulation rate of 20 to 50 Hertz over several hours). These studies resulted in the construction of a rapid high magnetic field strength device which was suitable for safety studies.
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The last decades of work in the Perl laboratory were principally devoted to characterizing the functional organization of the superficial dorsal horn of the spinal cord and understanding how spinal neurons located within these regions interact with one another to process signals arising from the periphery. These experiments involved recording from neurons responsive to various types of primary afferent input and correlating these functional signatures with morphological features of the spinal neurons in question. This work in part resulted in the systematic categorization by Timothy Grudt and Perl of functionally characterized spinal neurons based on their morphological features and location within the dorsal horn.Grudt TJ and Perl ER. Correlations between neuronal morphology and electrophysiological features in the rodent superficial dorsal horn.
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Ball earned her A.B. from Columbia University in 1922. She then worked as an assistant in psychology for Karl Lashley at the University of Minnesota from 1923–1926. In 1926, Ball published her first paper in "The female sex cycle as a factor in learning in the rat," one of the first papers on the role of hormones in learning and memory. She also later published a study with Lashley, “Spinal conduction and kinesthetic sensitivity in the maze habit,” which demonstrated that rats trained to run a maze can still run the maze without afferent sensory input via the spinal cord. From January to June 1924, Ball accompanied Robert Yerkes on the University of California-sponsored trip to Cuba to visit Madame Rosalía Abreu’s primate colony.
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Women can experience orgasm with vibration to the cervix regardless of level or completeness of injury; the sensation is the same as uninjured women experience. The peripheral nerves of the parasympathetic nervous system that carry messages to the brain (afferent nerve fibers) may explain why people with complete SCI feel sexual and climactic sensations. One proposed explanation for orgasm in women despite complete SCI is that the vagus nerve bypasses the spinal cord and carries sensory information from the genitals directly to the brain. Women with complete injuries can achieve sexual arousal and orgasm through stimulation of the clitoris, cervix, or vagina, which are each innervated by different nerve pathways, which suggests that even if SCI interferes with one area, function might be preserved in others.
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This generates the best wave reflection and image. Ultrasonic approach accurately locates the depth of the nerve and identifies surrounding anatomical structures of interest, such as blood vessels and bony structures, which may affect the placement of a microelectrode. A particular advantage is that the ultrasonic approach visualizes the electrode and the nerve at the same time, thereby facilitating electrode manipulation to reach the nerve. Once the electrode tip is in the nerve, small adjustments are required, first, to penetrate the sheath of an individual fascicle and, second, to take the tip to contact nerve fibers of the kind you are interested to explore, be it multi-unit sympathetic activity or single unit activity of either a myelinated afferent or a small unmyelinated fibres.
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After cloning two distinct genes for 5-HT1B and 5-HT1D receptors, a better insight into distribution and expression in different tissues was gained, except in brain tissue where they are overlapping in several areas. Most mammalian species, including humans, have 5-HT1D binding sites widely distributed throughout the central nervous system. 5-HT1D receptors are found in all areas of the brain but they differ in quantity at each area. An important initiator of head pain is suggested to be the activation of trigeminovascular afferent nerves which upon activation releases neuropeptides such as CGRP, substance P and neurokinin A. Also they are thought to promote neurogenic inflammatory response important for sensitization of sensory afferents, and also transmission and generation of head pain centrally.
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Motor nerve of Ox A motor nerve is a nerve located in the central nervous system (CNS), usually the spinal cord, that sends motor signals from the CNS to the muscles of the body. This is different from the motor neuron, which includes a cell body and branching of dendrites, while the nerve is made up of a bundle of axons. Motor nerves act as efferent nerves which carry information out from the CNS, as opposed to afferent nerves (also called sensory nerves), which send signals from sensory receptors in the periphery to the CNS. There are also nerves that serve as both sensory and motor nerves called mixed nerveMotor nerve fibers transduce signals from the CNS to peripheral neurons of proximal muscle tissue.
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Ghrelin is a participant in regulating the complex process of energy homeostasis which adjusts both energy input – by adjusting hunger signals – and energy output – by adjusting the proportion of energy going to ATP production, fat storage, glycogen storage, and short-term heat loss. The net result of these processes is reflected in body weight, and is under continuous monitoring and adjustment based on metabolic signals and needs. At any given moment in time, it may be in equilibrium or disequilibrium. Gastric-brain communication is an essential part of energy homeostasis, and several communication pathways are probable, including the gastric intracellular mTOR/S6K1 pathway mediating the interaction among ghrelin, nesfatin and endocannabinoid gastric systems, and both afferent and efferent vagal signals.
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Dendritic arbor formation for pyramidal neurons in the cortices occurs progressively beginning in late embryonic stages of development and extending well into post-natal periods. Many dendrites of pyramidal neurons in deep layers branch and form connections in layer IV, while some extend to more superficial layers. Pyramidal cell dendrites in layer III branch to form arbors in layer I. Thalamocortical afferents will make synaptic contact with dendrites in layer IV while myriad of other inputs will meet dendrites in layer I. The post-synaptic structure is driven in part by signals from incoming afferent fibers and through life there is plasticity in the synapses. The formation of these arbors is regulated by the strength of local signals during development.
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The EPSPs that converge on the pyramidal neurons through direct afferent fibers ending in the upper part of the apical dendrites cause a flow of charged ions (a current) between points at different potentials within and outside neurons. The positive ions then enter the cell following concentration and electrical charge gradient and propagate to the rest of the neuron. EPSPs from the distal apical dendrites create a current starting from the apical part nearest to the synapse (where the magnitude is greater) toward the cell body because the resistance to this flow is less. The current perpendicular (or radial) to the apical dendrite is accompanied by a magnetic field that propagates orthogonally (or tangentially) to the current along the extracellular side of the cell membrane.
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Research pre- dating the Arons' coining of the term "high sensitivity" includes that of German medicine professor Wolfgang Klages, who argued in the 1970s that the phenomenon of sensitive and highly sensitive humans is "biologically anchored" and that the "stimulus threshold of the thalamus" is much lower in these persons. As a result, said Klages, there is a higher permeability for incoming signals from afferent nerve fibers so that they pass "unfiltered" to the cerebral cortex. The Arons (1997) recognized psychologist Albert Mehrabian's (1976, 1980, 1991) concept of filtering the "irrelevant", but wrote that the concept implied that the inability of HSPs' (Mehrabian's "low screeners") to filter out what is irrelevant would imply that what is relevant is determined from the perspective of non-HSPs ("high screeners").
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The pallial portions build the analytic or perceptual end of this complex, whereas the subpallial portions represent the corresponding output or efferent functional pole. The olfactory bulb is a peculiar pallial outgrowth (maybe induced by the primary olfactory fibers afferent to it, coming from the sensory neurons developed in the olfactory placode) whose projection neurons (the mitral and tufted neurons) are pallial in origin and accordingly excitatory. In contrast, the superfial periglomerulary neurons, various intermediate interneurons and the deep granule cells are all of subpallial origin and migrate tangentially out of the striatal part of the subpallium (apparently from a dorsal subsector of this domain) through the so-called rostral migratory stream into the olfactory bulb. These extremely numerous subpallial cells are all inhibitory.
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The pyriform cortex is a type of allocortex that corresponds to the rostral half of the uncus. Its strongest afferent connections are from the olfactory bulb. Although the olfactory cortex comprises all the “areas in the rostro-ventral portion of the forebrain which receive direct projections from the olfactory bulb,” including the anterior olfactory nucleus, olfactory tubercle, the pyriform cortex, the entorhinal cortex, the insular cortex, and the amygdala, the pyriform cortex is considered synonymous with the olfactory cortex because it is “by far the largest cortical area primarily involved in perception and learning of olfactory stimuli.” It is a type of paleocortex, which means that it older than and has fewer layers than neocortex but is more recent than and contains more layers than archicortex.
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Also, synchronous afferent stimulation of peripheral muscles induces organizational changes in motor representations, characterized both by an increase in map size of stimulated muscles and a reduction in map separation, as assessed using transcranial magnetic stimulation. The cross-connectivity between areas that are normally segregated in the sensory cortex may prevent normal sensorimotor feedback and so contribute to the observed co-contraction of antagonist muscle groups, and inappropriately timed and sequenced movements that underlie the symptoms of focal dystonia. It is hypothesized that a deficit in inhibition caused by a genetically mediated loss of inhibitory interneurons may be the underlying cause of the deficits observed in dystonia. While usually painless, in some instances the sustained contraction and abnormal posturing in dystonia cause pain.
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The cerebral cortex is connected to various subcortical structures such as the thalamus and the basal ganglia, sending information to them along efferent connections and receiving information from them via afferent connections. Most sensory information is routed to the cerebral cortex via the thalamus. Olfactory information, however, passes through the olfactory bulb to the olfactory cortex (piriform cortex). The majority of connections are from one area of the cortex to another, rather than from subcortical areas; Braitenberg and Schüz (1998) claim that in primary sensory areas, at the cortical level where the input fibres terminate, up to 20% of the synapses are supplied by extracortical afferents but that in other areas and other layers the percentage is likely to be much lower.
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One factor at the forefront of recent research is in the pain-potentiating synapse located in the dorsal horn of the spinal cord and the role of astrocytes in encapsulating these synapses. Garrison and co- workers were the first to suggest association when they found a correlation between astrocyte hypertrophy in the dorsal horn of the spinal cord and hypersensitivity to pain after peripheral nerve injury, typically considered an indicator of glial activation after injury. Astrocytes detect neuronal activity and can release chemical transmitters, which in turn control synaptic activity. In the past, hyperalgesia was thought to be modulated by the release of substance P and excitatory amino acids (EAA), such as glutamate, from the presynaptic afferent nerve terminals in the spinal cord dorsal horn.
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The physiological type occurs prior to twenty-eight weeks after conception and tend to last five to ten minutes. These hiccups are part of fetal development and are associated with the myelination of the phrenic nerve, which primarily controls the thoracic diaphragm. The phylogeny hypothesis explains how the hiccup reflex might have evolved, and if there is not an explanation it may explain hiccups as an evolutionary remnant, held over from our amphibious ancestors. This hypothesis has been questioned because of the existence of the afferent loop of the reflex, the fact that it does not explain the reason for glottic closure, and because the very short contraction of the hiccup is unlikely to have a significant strengthening effect on the slow-twitch muscles of respiration.
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There are two types of afferent neurons found in the cochlear nerve: Type I and Type II. Each type of neuron has specific cell selectivity within the cochlea. The mechanism that determines the selectivity of each type of neuron for a specific hair cell has been proposed by two diametrically opposed theories in neuroscience known as the peripheral instruction hypothesis and the cell autonomous instruction hypothesis. The peripheral instruction hypothesis states that phenotypic differentiation between the two neurons are not made until after these undifferentiated neurons attach to hair cells which in turn will dictate the differentiation pathway. The cell autonomous instruction hypothesis states that differentiation into Type I and Type II neurons occur following the last phase of mitotic division but preceding innervations.
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Brainstem nuclei: Red = Motor; Blue = Sensory; Dark blue = Trigeminal nucleus All sensory information from the face, both touch-position and pain-temperature, is sent to the trigeminal nucleus. In classical anatomy most sensory information from the face is carried by the fifth nerve, but sensation from parts of the mouth, parts of the ear and parts of the meninges is carried by general somatic afferent fibers in cranial nerves VII (the facial nerve), IX (the glossopharyngeal nerve) and X (the vagus nerve). All sensory fibers from these nerves terminate in the trigeminal nucleus. On entering the brainstem, sensory fibers from V, VII, IX and X are sorted and sent to the trigeminal nucleus (which contains a sensory map of the face and mouth).
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Sphenoid wing meningiomas are diagnosed by the combination of suggestive symptoms from the history and physical and neuroimaging by magnetic resonance imaging (MRI) or computer averaged tomography (CT). Tumors growing in the inner wing (clinoidal) most often cause direct damage to the optic nerve leading especially to a decrease in visual acuity, progressive loss of color vision, defects in the field of vision (especially cecocentral), and an afferent pupillary defect. If the tumor continues to grow and push on the optic nerve, all vision will be lost in that eye as the nerve atrophies. Proptosis, or anterior displacement of the eye, and palpebral swelling may also occur when the tumor impinges on the cavernous sinus by blocking venous return and leading to congestion.
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Second is the operation of Sherrington's Law describing reciprocal inhibition between agonist-antagonist muscle pairs, and by implication the stretching of extraocular muscle that must occur whenever Sherrington's Law is made to fail, thereby causing an unrelaxed (contracted) muscle to be stretched. Finally, there is the critical presence of afferent output to the Vagus nerves as a direct result of eye muscle stretch or traction. Thus, 10th nerve stimulation resulting from eye muscle stretch is proposed as the cause of motion sickness. The theory explains why labyrinthine-defective individuals are immune to motion sickness; why symptoms emerge when undergoing various body-head accelerations; why combinations of voluntary and reflexive eye movements may challenge the proper operation of Sherrington's Law, and why many drugs that suppress eye movements also serve to suppress motion sickness symptoms.
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There is much debate about the true cause and mechanism of the sneezing fits brought about by the photic sneeze reflex. Sneezing occurs in response to irritation in the nasal cavity, which results in an afferent nerve fiber signal propagating through the ophthalmic and maxillary branches of the trigeminal nerve to the trigeminal nerve nuclei in the brainstem. The signal is interpreted in the trigeminal nerve nuclei, and an efferent nerve fiber signal goes to different parts of the body, such as mucous glands and the thoracic diaphragm, thus producing a sneeze. The most obvious difference between a normal sneeze and a photic sneeze is the stimulus: normal sneezes occur due to irritation in the nasal cavity, while the photic sneeze can result from a wide variety of stimuli.
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Following these findings with funding from the Whitaker Foundation,The Development of Methods for the Analysis of Non-Time-Stable Brain Responses. Whitaker Foundation grant, 1985-1989 Sgro developed technology and techniques to analyze evoked potentials based on stimulation run by an ultra fast (i.e. hundreds of hertz) pseudorandom m-sequences.Marmarmelis, P. and Marmarmelis, V.Z., Analysis of PhysiologicalSystem, Plenum Press, New York, NY, 1978. This work was demonstrated to be a more effective method of identification and predictor of sub-clinical diseases or damage such as mortality from status epilepticus"Assessment of Afferent and Efferent Neuropathways in Severe Head Injury," NIH Program Project Grant #2P01NS012587, 1989-1992.. (diseases that otherwise went undetected until they become severe enough to qualify as clinically apparent when compared to conventional evoked potentials).
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The first publication produced from the couple's collaboration was a monograph of the myelination of the anterior part of the brain in the cat. The finding led to the Vogts' questioning of the German neurologist Paul Flechsig's doctrine of association centers. Together they pursued advanced neuropathological research, publishing their findings on both cyto- and myelo-architecture in the central nervous system and on the functional anatomy of the basal ganglia. In 1909, Vogt-Mugnier published La myelocytoarchitecture du thalamus du cercopithèque (Myelocytoarchitecture of the Thalamus of the Cercopithecus), in which she reported her experiments in tracing afferent fibers to the thalamic ventral nuclear group. In 1911, Vogt- Mugnier rediscovered the so-called ‘status marmoratus’ of the corpus striatum, characterized by slow, writhing, purposeless movements mainly affecting the hands and face.
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Severe hypotonia in infancy commonly known as floppy baby syndrome. Recognizing hypotonia, even in early infancy, is usually relatively straightforward, but diagnosing the underlying cause can be difficult and often unsuccessful. The long-term effects of hypotonia on a child's development and later life depend primarily on the severity of the muscle weakness and the nature of the cause. Some disorders have a specific treatment but the principal treatment for most hypotonia of idiopathic or neurologic cause is physical therapy, occupational therapy for remediation, and/or music therapy. Hypotonia is thought to be associated with the disruption of afferent input from stretch receptors and/or lack of the cerebellum’s facilitatory efferent influence on the fusimotor system, the system that innervates intrafusal muscle fibers thereby controlling muscle spindle sensitivity.
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The routine four-channel montages proposed in the International Federation of Clinical Neurophysiology (IFCN) guidelines explore the afferent peripheral volley, the segmental spinal responses at the neck and lumbar spine levels, as well as the subcortical far-field and early cortical SEPs, using scalp electrodes placed in the parietal and frontal regions for upper limb SEPs and at the vertex for lower limb SEPs. Median nerve SEP begins with the delivery of an electrical stimulus to that nerve at the wrist. A 100–300 microsecond square wave electrical pulse is delivered at intensities strong enough to cause a 1–2 cm thumb twitch. Upon delivery of such a stimulus, nerve action volleys travel up sensory fibers and motor fibers to the shoulder, producing a peak as they enter.
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An axon (from Greek ἄξων áxōn, axis), or nerve fiber (or nerve fibre: see spelling differences), is a long, slender projection of a nerve cell, or neuron, in vertebrates, that typically conducts electrical impulses known as action potentials away from the nerve cell body. The function of the axon is to transmit information to different neurons, muscles, and glands. In certain sensory neurons (pseudounipolar neurons), such as those for touch and warmth, the axons are called afferent nerve fibers and the electrical impulse travels along these from the periphery to the cell body, and from the cell body to the spinal cord along another branch of the same axon. Axon dysfunction has caused many inherited and acquired neurological disorders which can affect both the peripheral and central neurons.
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After the Royal Free Hospital outbreak, a disorder with similar symptoms was found among the general population and the epidemic form came to be considered the exception. Pathology findings, both in monkeys and in rare human casualties, led to the conclusion that the disorder was caused by inflammation of the brain and the spinal cord, particularly the afferent nerve roots, perhaps with neuroimmune etiology. In the 1960s and 1970s, chronic fatigue symptoms were often attributed to chronic brucellosis, but typically people were seen as having psychiatric disorders, in particular depression. Epidemic cases of benign myalgic encephalomyelitis were called mass hysteria by psychiatrists McEvedy and Beard in 1970, provoking criticism in letters to the editor of the British Medical Journal by outbreak researchers, attending physicians, and physicians who fell ill.
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The olfactory tract is a bilateral bundle of afferent nerve fibers from the mitral and tufted cells of the olfactory bulb that connects to several target regions in the brain, including the piriform cortex, amygdala, and entorhinal cortex. It is a narrow white band, triangular on coronal section, the apex being directed upward. It lies in the olfactory sulcus on the inferior surface of the frontal lobe, and divides posteriorly into two striae, a medial olfactory stria and a lateral olfactory stria. Fibers of the olfactory tract appear to end in the antero-lateral part of the olfactory tubercle, the dorsal and external parts of the anterior olfactory nucleus, the frontal and temporal parts of the prepyriform area, the cortico-medial group of amygdaloid nuclei and the nucleus of the stria terminalis.
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The macula densa region of the kidney's juxtaglomerular apparatus is another modulator of blood osmolality. The macula densa responds to changes in osmotic pressure through changes in the rate of sodium ion (Na+) flow through the nephron. Decreased Na+ flow stimulates tubuloglomerular feedback to autoregulate, a signal (thought to be regulated by adenosine) sent to the nearby juxtaglomerular cells of the afferent arteriole, causing the juxtaglomerular cells to release the protease renin into circulation. Renin cleaves the zymogen angiotensinogen, always present in plasma as a result of constitutive production in the liver, into a second inactive form, angiotensin I, which is then converted to its active form, angiotensin II, by angiotensin converting enzyme (ACE), which is widely distributed in the small vessels of the body, but particularly concentrated in the pulmonary capillaries of the lungs.
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Furthermore, response to natural rewards such as sucrose does not appear to be attenuated. General affective blunting may explain "anhedonic" symptoms in depression, as meta analysis of both positive and negative stimuli reveal reduced rating of intensity. As anhedonia is a prominent symptom of depression, direct comparison of depressed with healthy subjects reveals increased activation of the subgenual anterior cingulate cortex (sgACC), and reduced activation of the ventral striatum, and in particular the nucleus accumbens (NAcc) in response to positive stimuli. Although the finding of reduced NAcc activity during reward paradigms is fairly consistent, the NAcc is made up of a functionally diverse range of neurons, and reduced blood-oxygen-level dependent (BOLD) signal in this region could indicate a variety of things including reduced afferent activity or reduced inhibitory output.
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These re-afferent sensory signals will trigger activity in neurons responding to the sight, sound, and feel of the action. Because the activity of these sensory neurons will consistently overlap in time with those of the motor neurons that caused the action, Hebbian learning predicts that the synapses connecting neurons responding to the sight, sound, and feel of an action and those of the neurons triggering the action should be potentiated. The same is true while people look at themselves in the mirror, hear themselves babble, or are imitated by others. After repeated experience of this re-afference, the synapses connecting the sensory and motor representations of an action are so strong that the motor neurons start firing to the sound or the vision of the action, and a mirror neuron is created.
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In neuroscience, an F wave is one of several motor responses which may follow the direct motor response (M) evoked by electrical stimulation of peripheral motor or mixed (sensory and motor) nerves. F-waves are the second of two late voltage changes observed after stimulation is applied to the skin surface above the distal region of a nerve, in addition to the H-reflex (Hoffman's Reflex) which is a muscle reaction in response to electrical stimulation of innervating sensory fibers. Traversal of F-waves along the entire length of peripheral nerves between the spinal cord and muscle, allows for assessment of motor nerve conduction between distal stimulation sites in the arm and leg, and related motoneurons (MN's) in the cervical and lumbosacral cord. F-waves are able to assess both afferent and efferent loops of the alpha motor neuron in its entirety.
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With this discovery, the team set out to perform nerve transfer surgery specifically aimed to reinnervate sensory feedback. A piece of skin near or over the targeted muscle was denervated, thus the afferent nerve fibers were allowed to reinnervate the skin. In a case of a woman patient with left arm amputation at the humeral neck, the supraclavicular sensory nerve was cut, the proximal end was ligated to prevent regeneration and reinnervation, and the distal end was coapted end-to-side to the ulnar nerve. The intercostobrachial cutaneous nerve was treated with the same method, with the distal end coapted to the median nerve. This technique has been dubbed “transfer sensation”, and it has the potential of providing useful sensory feedback, such as pressure sensing, to help the patient judge the amount of force to be exerted.
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Supraoptic neurons have typically 1-3 large dendrites, most of which projecting ventrally to form a mat of process at the base of the nucleus, called the ventral glial lamina. The dendrites receive most of the synaptic terminals from afferent neurons that regulate the supraoptic neurons, but neuronal dendrites are often actively involved in information processing, rather than being simply passive receivers of information. The dendrites of supraoptic neurons contain large numbers of neurosecretory vesicles that contain oxytocin and vasopressin, and they can be released from the dendrites by exocytosis. The oxytocin and vasopressin that is released at the posterior pituitary gland enters the blood, and cannot re- enter the brain because the blood–brain barrier does not allow oxytocin and vasopressin through, but the oxytocin and vasopressin that is released from dendrites acts within the brain.
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This theory postulates that activation of large diameter, myelinated primary afferent fibers suppresses the response of dorsal horn neurons to input from small, unmyelinated primary afferents. A simple SCS system consists of three different parts. First, microelectrodes are implanted in the epidural space to deliver stimulation pulses to the tissue. Second, an electrical pulse generator implanted in the lower abdominal area or gluteal region while is connected to the electrodes via wires, and third a remote control to adjust the stimulus parameters such as pulse width and pulse rate in the PG. Improvements have been made in both the clinical aspects of SCS such as transition from subdural placement of contacts to epidural placement, which reduces the risk and morbidity of SCS implantation, and also technical aspects of SCS such as improving percutaneous leads, and fully implantable multi-channel stimulators.
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In neuroanatomy, the cingulum is a nerve tract – a collection of axons – projecting from the cingulate gyrus to the entorhinal cortex in the brain, allowing for communication between components of the limbic system. It forms the white matter core of the cingulate gyrus, following it from the subcallosal gyrus of the frontal lobe beneath the rostrum of corpus callosum to the parahippocampal gyrus and uncus of the temporal lobe.J. Edward Bruni, Donald Montemurro, Human Neuroanatomy: A Text, Brain Atlas and Laboratory Dissection Guide, Oxford University Press, 2009 Neurons of the cingulum receive afferent fibers from the parts of the thalamus that are associated with the spinothalamic tract. This, in addition to the fact that the cingulum is a central structure in learning to correct mistakes, indicates that the cingulum is involved in appraisal of pain and reinforcement of behavior that reduces it.
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The company is due up to $510 million more, which is tied to clinical, regulatory and commercial milestones. Merck & Co. will bring in CM-24, an antibody designed to block the immune checkpoint CEACAM1. In January 2016 Merck & Co. announced two new partnerships; the first with Quartet Medicine and its small molecule pain treatments, the second with Complix investigating intracellular cancer targets, with both collaborations potentially generating up to $595 million and $280 million respectively. Days later the company announced it would acquire IOmet Pharma, with IOmet becoming a wholly owned subsidiary of Merck & Co. The acquisition includes IOmets indoleamine-2,3-dioxygenase 1 (IDO), tryptophan 2,3-dioxygenase (TDO), and dual-acting inhibitors. In June, the company announced its acquisition of Afferent Pharmaceuticals for $1.25 billion, gaining Afferents lead compound—AF-219—used to block P2X3 receptors.
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The afferent convergence mechanisms, which can > create signs and symptoms that are virtually indistinguishable with respect > to their somatic vs. visceral etiologies, suggest it is not unreasonable > that this somatic visceral-disease mimicry could very well account for the > "cures" of presumed organ disease that have been observed over the years in > response to various somatic therapies (e.g., spinal manipulation, > acupuncture, Rolfing, Qi Gong, etc.) and may represent a common phenomenon > that has led to "holistic" health care claims on the part of such clinical > disciplines. Considering this phenomenon, Seaman suggests that the chiropractic concept of joint complex (somatic) dysfunction should be incorporated into the differential diagnosis of pain and visceral symptoms because these dysfunctions often generate symptoms similar to those produced by true visceral disease and notes that this mimicry leads to unnecessary surgical procedures and medications.
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Since the neurons of the ELL receive both a corollary discharge (another term for an efference copy) of the motor output commands sent to the EOD, and afferent input from the electrosensory receptors, the animal is able to eliminate predictable inputs produced by its own motor output. The system is able to filter the expected input from the EOD, while signals which are unexpected, arriving at odd intervals with regard to the motor command are effectively strengthened by the learning rule. This allows the extraction of information about objects which cause an alteration in the flow of the electric field around the fish, highlighting changes while discarding uninformative sensory inputs. The adaptation of these synapses, though, will only increase the strength of a synaptic connection until the resulting excitation aids in activation of a broad-spike wave.
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Noxious input to the spinal cord is known to produce central sensitization, which consists of allodynia, exaggeration of pain, and punctuate hyperalgesia, extreme sensitivity to pain. Two types of mechanical hyperalgesia can occur: 1) touch that is normally painless in the uninjured surroundings of a cut or tear can trigger painful sensations (touch-evoked hyperalgesia), and 2) a slightly painful pin prick stimulation is perceived as more painful around a focused area of inflammation (punctuate hyperalgesia). Touch-evoked hyperalgesia requires continuous firing of primary afferent nociceptors, and punctuate hyperalgesia does not require continuous firing which means it can persist for hours after a trauma and can be stronger than normally experienced. In addition, it was found that patients with neuropathic pain, histamine ionophoresis resulted in a sensation of burning pain rather than itch, which would be induced in normal healthy patients.
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A large sodium chloride concentration is indicative of an elevated GFR, while low sodium chloride concentration indicates a depressed GFR. Sodium chloride is sensed by the macula densa mainly by an apical Na-K-2Cl cotransporter (NKCC2). The relationship between the TGF and NKCC2 can be seen through the administration of loop diuretics like furosemide. Furosemide blocks NaCl reabsorption mediated by the NKCC2 at the macula densa, which leads to increased renin release. Excluding loop diuretic use, the usual situation that causes a reduction in reabsorption of NaCl via the NKCC2 at the macula densa is a low tubular lumen concentration of NaCl. Reduced NaCl uptake via the NKCC2 at the macula densa leads to increased renin release, which leads to restoration of plasma volume, and to dilation of the afferent arterioles, which leads to increased renal plasma flow and increased GFR.
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The parabrachial nuclei receive visceral afferent information from a variety of sources in the brainstem, including much input from the solitary nucleus, which brings taste information and information about the remainder of the body. The external, dorsal, internal and superior lateral subnuclei also receive input from the spinal and trigeminal dorsal horn, mainly concerned with pain and other visceral sensations. Outputs from the parabrachial nucleus originate from specific subnuclei and target forebrain sites involved in autonomic regulation, including the lateral hypothalamic area, ventromedial, dorsomedial, and arcuate hypothalamic nuclei, the median and lateral preoptic nuclei, the substantia innominate, the ventroposterior parvicellular and intralaminar thalamic nuclei, the central nucleus of the amygdala, and the insular and infralimbic cortex. The subparabrachialnucleus and lateral crescent send efferents to the nucleus of the solitary tract, ventrolateral medulla, and spinal cord, where they target many respiratory and autonomic cell groups.
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For example, in a person with abnormal left direct reflex and abnormal right consensual reflex (with normal left consensual and normal right direct reflexes), which would produce a left Marcus Gunn pupil, or what is called afferent pupillary defect, by physical examination: # Left consensual reflex is normal, therefore segments 2, 4, and 7 are normal. Lesion is not located in any of these segments. # Right direct reflex is normal, therefore segments 2, 6, and 8 are normal. Combining with earlier normals, segments 2, 4, 6, 7, and 8 are all normal. # Remaining segments where lesion may be located are segments 1, 3, and 5. Possible combinations and permutations are: (a) segment 1 only, (b) segment 3 only, (c) segment 5 only, (d) combination of segments 1 and 3, (e) combination of segments 1 and 5, (f) combination of segments 3 and 5, and (g) combination of segments 1, 3, and 5.
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Vagus nerve stimulation (VNS) therapy using a neurostimulator implanted in the chest is a treatment used since 1997 to control seizures in epilepsy patients and has been approved for treating drug- resistant cases of clinical depression. A non-invasive VNS device that stimulates an afferent branch of the vagus nerve is also being developed and will soon undergo trials. Clinical trials have started in Antwerp, Belgium, using VNS for the treatment of tonal tinnitus after a breakthrough study published in early 2011 by researchers at the University of Texas - Dallas showed successful tinnitus-suppression in rats when tones were paired with brief pulses of stimulation of the vagus nerve. VNS may also be achieved by one of the vagal maneuvers: holding the breath for 20–60 seconds, dipping the face in cold water, coughing, or tensing the stomach muscles as if to bear down to have a bowel movement.
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The name is derived from the surgeon who first described it (César Roux) and the stick-figure representation. Diagrammatically, the Roux-en-Y anastomosis looks a little like the letter Y. Typically, the two upper limbs of the Y represent (1) the proximal segment of stomach and the distal small bowel it joins with and (2) the blind end that is surgically divided off, and the lower part of the Y is formed by the distal small bowel beyond the anastomosis. Roux-en-Ys are used in several operations and collectively called Roux operations. When describing the surgery, the Roux limb is the efferent or antegrade limb that serves as the primary recipient of food after the surgery, while the hepatobiliary or afferent limb that anastomoses with the biliary system serves as the recipient for biliary secretions, which then travel through the excluded small bowel to the distal anastomosis at the mid jejunum to aid digestion.
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First, the belief that mental illness was organic in nature, and reflected an underlying brain pathology; next, that the nervous system was organized according to an associationist model comprising an input or afferent system (a sensory center), a connecting system where information processing took place (an association center), and an output or efferent system (a motor center); and, finally, a modular conception of the brain whereby discrete mental faculties were connected to specific regions of the brain. Burckhardt's hypothesis was that by deliberately creating lesions in regions of the brain identified as association centers a transformation in behavior might ensue. According to his model, those mentally ill might experience "excitations abnormal in quality, quantity and intensity" in the sensory regions of the brain and this abnormal stimulation would then be transmitted to the motor regions giving rise to mental pathology. He reasoned, however, that removing material from either of the sensory or motor zones could give rise to "grave functional disturbance".
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There are two types: autonomic reflex arc (affecting inner organs) and somatic reflex arc (affecting muscles). Autonomic reflexes sometimes involve the spinal cord and some somatic reflexes are mediated more by the brain than the spinal cord. During a somatic reflex, nerve signals travel along the following pathway: # Somatic receptors in the skin, muscles and tendons # Afferent nerve fibers carry signals from the somatic receptors to the posterior horn of the spinal cord or to the brainstem # An integrating center, the point at which the neurons that compose the gray matter of the spinal cord or brainstem synapse # Efferent nerve fibers carry motor nerve signals from the anterior horn to the muscles # Effector muscle innervated by the efferent nerve fiber carries out the response. A reflex arc, then, is the pathway followed by nerves which (a.) carry sensory information from the receptor to the spinal cord, and then (b.) carry the response generated by the spinal cord to effector organs during a reflex action.
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The groups are, caudal to rostral: nasal/infraorbital (I), supraorbital (II), and supratemporal/post-orbital (III).Bleckmann, H., and Mohr, C. (1998) "Electrophysiology of the Cephalic Lateral Line of the Surface-Feeding Fish Aplocheilus lineatus". Comparative Biochemistry and Physiology 119A(3):807-815 Each neuromast is a cluster of hair-cell bundles arranged in a line and numbering in the 10s to 100s. Each bundle of hair cells is covered in a gelatinous capulla which the capillary waves actually make contact with and in doing so cause afferent neurons to fire.McHenry, M.J. and van·Netten, S.M. (2007) "The flexural stiffness of superficial neuromasts in the zebrafish (Danio rerio) lateral line". Journal of Experimental Biology 210:4244-4253, cited in Schwarz 2011 Neuromasts are similar in structure to canal organs in the lateral line canal system: they are housed in sacs of connective tissue between the skull and skin, and are connected to the water and water surface via canals and canal pores.
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" They also stated that light "constant pressure on the clitoris produced an initial burst of single unit firing (maximum frequencies 170–255 Hz) followed by rapid adaptation and a sustained firing (maximum 40 Hz), which was maintained during the stimulation" and that further examination of tonic firing "indicate that the clitoris is innervated by mechano-sensitive myelinated afferent fibers in the pudental nerve which project centrally to the region of the dorsal commissure in the L7-S1 spinal cord". The external phenotype and reproductive behavior of 21 freemartin sheep and two male pseudohermaphrodite sheep were recorded with the aim of identifying any characteristics that could predict a failure to breed. The vagina's length and the size and shape of the vulva and clitoris were among the aspects analyzed. While the study reported that "a number of physical and behavioural abnormalities were detected," it also concluded that "the only consistent finding in all 23 animals was a short vagina which varied in length from 3.1 to 7.0 cm, compared with 10 to 14 cm in normal animals.
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The understanding at the single-cell level of the IT cortex and its role of utilizing memory to identify objects and or process the visual field based on color and form visual information is a relatively recent in neuroscience. Early research indicated that the cellular connections of the temporal lobe to other memory associated areas of the brain – namely the hippocampus, the amygdala, the prefrontal cortex, among others. These cellular connections have recently been found to explain unique elements of memory, suggesting that unique single-cells can be linked to specific unique types and even specific memories. Research into the single-cell understanding of the IT cortex reveals many compelling characteristics of these cells: single-cells with similar selectivity of memory are clustered together across the cortical layers of the IT cortex; the temporal lobe neurons have recently been shown to display learning behaviors and possibly relate to long-term memory; and, cortical memory within the IT cortex is likely to be enhanced over time thanks to the influence of the afferent-neurons of the medial-temporal region.
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When the efference copy is no longer normally generated, then the afferent return from the limb associated with the self-generated movement is mis-perceived as externally produced "ex- afference" since it is no longer correlated with or canceled out by the efference copy. As a result, the development of the sense that a movement is not internally generated even though it actually is (i.e. the failure of the sense of agency to emerge in conjunction with the movement), could indicate a failure of the generation of the efference copy signal associated with the normal premotor process through which the movement is prepared for execution. Since there is no disturbance of the sense of ownership of the limb (a concept discussed in the Wikipedia entry on sense of agency) in this situation, and there is no clearly apparent physically ostensible explanation for how the owned limb could be moving in a purposive manner without an associated sense of agency, effectively through its own power, a cognitive dissonance is created which may be resolved through the assumption that the goal-directed limb movement is being directed by an "alien" unidentifiable external force with the capacity for directing goal-directed actions of one's own limb.
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