White brain matter is important because it contains nerve fibers that allow signals to travel faster and more efficiently, plus protects those nerve fibers from injury, according to Medline Plus.
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But newly connected nerve fibers do not instantly carry current.
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The scans reveal the complex network of nerve fibers connecting the different brain areas.
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"The body temperature will drop quite markedly," when you activate the nerve fibers, Julius says.
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When a muscle or ligament tears, so do the nerve fibers embedded in that tissue.
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For example, the new tissue can connect to nerve fibers, but it can't make them.
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The RGMA gene originates a signal that tells nerve fibers where they need to go.
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This technique reconstructs the orientation of bundles of nerve fibers by measuring multi-directional water diffusion.
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The nerve fibers advanced about a millimeter a day (about 24,000 times slower than a snail).
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The degenerative disorder affects the fatty covering that protects the brain's nerve fibers and has no cure.
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Her doctors suspected that this was a result of damaged nerve fibers that had only partially regenerated.
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The disease begins when a person's immune system attacks the coverings of nerve fibers throughout the body.
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A few months after the scaffolds and neural progenitor cells were implanted, nerve fibers from the rats' brains had connected to the new cells, which in turn connected with nerve fibers coming up from the rodents' lower extremities, allowing the rats to move their legs in a deliberate way.
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According to the latest research, one culprit may be pain-sensing nerve fibers deep within the inner ear.
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The nerve fibers release chemicals that increase blood flow and cause inflammation, which is why your lips swell up.
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After falling in, you will have about 10 minutes before your muscle and nerve fibers become too cold to function.
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"It pleases the nerve fibers," he said, all baritone to his voice, before disappearing into the chilled yellow muck again.
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Her immune system was stripping the fatty coating, called myelin, from her nerve fibers, impeding their ability to transmit signals.
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For one, there are orders of magnitude more nerve fibers in the arm than there are electrodes used in the USEA.
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What it shows: A slice of the corpus callosum, a thick band of nerve fibers connecting the two hemispheres of the brain.
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She went from doctor to doctor before finally receiving a diagnosis of small fiber neuropathy (which is damage to certain nerve fibers).
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While this picture seems like an iridescent alien butterfly, it's actually a rear view on nerve fibers inside a healthy adult human's brain.
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The hands still provided only faint movement and sensation, as the nerve fibers still had a ways to grow to reach his fingers.
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Myelin doesn't just protect our nerve fibers, though, it boosts the speed of the electrical signals that neurons use to communicate with one another.
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A balloon is inflated so it stretch the vein, in doing so transferring energy to the nerve fibers along the outside of the vein.
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They can "record from (listen to) or stimulate (talk to) small subsets of nerve fibers very selectively, and reasonably comprehensively," Clark explained via email.
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These nerve fibers are located mainly in the connective tissue found between muscle fibers, as well as the junction between the muscle and tendon.
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Gray matter contains most of your brain's 100 billion nerve cells, while white matter is filled with nerve fibers that connect the brain regions.
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Capsaicin binds to heat receptors located on pain nerve fibers throughout your body, tricking your brain into thinking parts of your body are literally burning.
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Although Marré and Hughes suffered serious headaches, "often, strokes do not hurt," Dr. Cole explains, because the brain doesn't have many pain-detecting nerve fibers.
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The core of a tooth, the pulp, holds the blood vessels and nerve fibers, while the bulk consists of a bone-like material called dentin.
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That suggested that whatever the problem was, it was affecting the nerve fibers in his arms and legs rather than in his brain or spine.
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Additionally, penises have nerves that run along the top side, and those nerve fibers are responsible for all the lovely sensations that come from sexual pleasure.
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White matter is located in the deep tissues of the brain, and it protects the nerve fibers that strengthen the speed of electrical signals in the brain.
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When you place your bare feet on the ground, each one of your 72,000 nerve fibers uptakes the electromagnetic pulse of the earth, which makes you instantly calmer.
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Many of the babies had other abnormalities, including brain swelling, disruptions in brain folds, underdeveloped brain structures and abnormalities in myelin, which forms protective sheaths on nerve fibers.
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ADEM typically occurs in the aftermath of an infection, causing intense swelling in the brain and spinal cord that damages myelin, the white protective coating surrounding nerve fibers.
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Denworth describes one bit of social neurobiology that in fact is found in our skin: special nerve fibers called CT afferents that, when stimulated, create a pleasant sensation.
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"Chronic pain 'highjacks' sensory nerve fibers, thereby making it harder or impossible for pleasurable stimuli to elicit a response," Murphy, who wasn't involved in the study, said by email.
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Others, like the indestructible tardigrades (or water bears), have done away with the complex rubric of nerve fibers found in their Cambrian forebears, in favor of more minimalistic systems.
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In this rare autoimmune disorder, the body's defense system mistakenly attacks the connections between the nerve fibers and the muscles they command, causing the muscles to tire out quickly.
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We learned from decades of studying boxing that multiple sub-concussive blows result in aggregate widespread tearing of nerve fibers and small blood vessels, and possibly to chronic traumatic encephalopathy.
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Gray matter in the brain contains the neuron cell bodies, whereas white matter contains bundles of nerve fibers and its job is to process and send signals along the spinal cord.
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This substance, the researchers wrote, could "restore the integrity of sharply severed nerve fibers or seal the membrane of damaged neurons," based on past research, by fusing the fibers back together.
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In addition to speeding up the process, the new technique can also detect some details that traditional methods may miss, like the spread of a tumor along nerve fibers, he said.
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However, this method proved to be problematic because each voxel is 1-3 cubic millimeters, which is large enough to contain several different populations of nerve fibers all coursing in different directions.
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The findings are the first from a large-scale trial of a drug that targets the Alzheimer's-related protein tau, which forms toxic tangles of nerve fibers associated with the fatal disease.
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Zika exposed patients have had other neurological problems as well, including acute disseminated encephalomyelitis, which causes inflammation of the myelin, the protective sheath covering nerve fibers in the brain and spinal cord.
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Taft suspected that Massimo's illness had a genetic origin and that one or more mutations had damaged the brain's myelin sheath, which protects the nerve fibers in the brain and spinal cord.
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Doctors knew that massaging the skin activated so-called large nerve fibers, which are specialized to detect subtle variations of touch; and that deeper, small fibers sounded the alarm of tissue damage.
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He comforts himself with the knowledge that the scientist who performed a 3-D scan of his brain praised his robust corpus callosum, the bundle of nerve fibers that connects the hemispheres.
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The neurologist performed a nerve-conduction study, during which a tiny electrode, inserted into the muscle, measures the electrical impulses the nerve fibers send to the brain when the muscle is working.
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In a proof of principle, researchers used neural progenitor cells to grow a kind of splice reconnecting severed nerve fibers coming from the rats' brains to the lower parts of the rodents' bodies.
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In the '70s, the American psychologist Julian Jaynes argued that all early humans suffered from hallucinations because their two brain hemispheres, connected by nerve fibers of the corpus callosum, were not fully integrated.
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What it shows: These balloon-animal-looking things are individual FODs from voxels in the optic chiasm, which is where half of the nerve fibers from each eye cross to the opposite hemisphere.
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The researchers were specifically interested in how a good HLE might affect structure and connections in the brain's white matter, the tissue made of nerve fibers that connect different parts of the brain.
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Those who suffered from migraines without aura saw that increased risk cut in half (34%), but they too could get lesions in the part of the brain that is made up of nerve fibers.
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M.S. is a condition in which an abnormal response of the body's immune system is directed against the central nervous system and attacks myelin, the coating of the nerve fibers, and the fibers themselves.
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The nerve fibers in the penis that are activated by temperature and pain are more relevant in sexual functioning—or the feel of a sexy touch—than the light touch that past researchers had done.
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They are started by an irritation of nerve fibers in the linings of the brain, causing pain, according to Dr. Patrick D. Lyden, chairman of the neurology department at Cedars-Sinai in the United States.
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A researcher at Duke University found that part of the body's response involves a protein known for inducing inflammation on the skin, "exciting" the nerve fibers in the skin and sending itchy signals to the brain.
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White matter is comprised of millions of bundles of nerve fibers; it acts as the "computer cables" that connect various parts of the brain, says senior author Rong Zhang, neurology professor at UT Southwestern's O'Donnell Brain Institute.
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When the myelin or nerve fibers are attacked and damaged, scar tissue, or sclerosis, is formed, which prevents the proper transmission of messages through the brain, spinal cord and optic nerves, producing a wide variety of symptoms.
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White matter is composed of millions of nerve fibers called axons and by using a sophisticated form of brain-scanning MRI technique, scientists are able to measure the movement of water molecules in the brain and along the axons.
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About two-thirds of your brain is made up of fat, which provides not only its cell membranes but also the myelin, the fatty insulating sheath that surrounds nerve fibers throughout your body and enables them to carry messages faster.
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Rebranding itself as "Axon" (as in the nerve fibers that connect neurons throughout the human body), the company said in a press release that it's "going 'all-in' to empower police officers" and will offer departments free cameras and storage for an entire year.
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"Our study shows that sensitivity to pain does not occur only in the skin's nerve [fibers], but also in this recently discovered pain-sensitive organ," said senior study author Patrik Ernfors, a pain researcher at Sweden's Karolinska Institute, in a release from the university.
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As I take in seven minutes of the children's animated show The Magic School Bus, Eden's team captures a 3-D scan of my brain, along with a colorful Diffusion Tensor Imaging scan that exposes my white matter—the tendrils of nerve fibers running through the various regions of my brain.
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"Freshly formed OEA travels to the nerve fibers that lie beneath the gut lining and tells them to send a satiety signal to the brain," said Daniele Piomelli, professor of anatomy and neurobiology, pharmacology and biological chemistry at the University of California, Irvine, who has studied OEA's role in appetite reduction.
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The second received a program of "pain neuroscience education," in which they learned about the function of neurons and synapses, the ways in which pain is transmitted along nerve fibers via the spinal cord to the brain, and how pain itself can modify central nervous system functions, producing pain with even the mildest stimulation.
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"The current study combines exquisite 3-D printing with neural progenitor cells to create a synthetic segment of spinal cord that enables some severed nerve fibers to regenerate from neural centers upstream from the injury site into parts of the spinal cord that have lost their normal inputs," Benowitz, who wasn't involved in the study, said by email.
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MS affects about 2.3 million people around the world, particularly women in more temperate climates like Canada and the northern US. Instead of protecting the body from foreign invaders, in patients with MS, the immune system turns on its host, in particular damaging the myelin, a protective coating around the nerve fibers in the brain and spinal cord.
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The performance opens with a poem by Tom Sleigh that, harking back to the amygdalae, compares the mourning braid to the mysterious workings of the grieving brain: "If you were to peer into the mourner's skull / where all this feeling is electrical signals / firing, what you'd see are nerve fibers, / long strands of tissue that look like dead people's hair / braided into amulets, lockets / in barrows and old tombs," chant two women in not-quite unison.
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As electrical stimuli have a greater effect over nerve fibers of a larger diameter, DPPs will in turn cause a larger degree of sodium conductance inactivation within such nerve fibers, thus nerve fibers of a smaller diameter will have a lower threshold current.
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Nerve fibers are classed into three types – group A nerve fibers, group B nerve fibers, and group C nerve fibers. Groups A and B are myelinated, and group C are unmyelinated. These groups include both sensory fibers and motor fibers. Another classification groups only the sensory fibers as Type I, Type II, Type III, and Type IV. An axon is one of two types of cytoplasmic protrusions from the cell body of a neuron; the other type is a dendrite.
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When blood flow stops, oxygen delivery stops and optic nerve fibers die.
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If an injury to the spine produces nothing worse than swelling, the symptoms may be transient, but if nerve fibers in the spine are actually destroyed, the loss of function is usually permanent. Experimental studies have shown that spinal nerve fibers attempt to regrow in the same way as nerve fibers, but in the spinal cord, tissue destruction usually produces scar tissue that cannot be penetrated by the regrowing nerves.
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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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Group A nerve fibers are one of the three classes of nerve fiber as generally classified by Erlanger and Gasser. The other two classes are the group B nerve fibers, and the group C nerve fibers. Group A are heavily myelinated, group B are moderately myelinated, and group C are unmyelinated. The other classification is a sensory grouping that uses the terms type Ia and type Ib, type II, type III, and type IV, sensory fibers.
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During the bud to cap stage of tooth development, the pioneer nerve fibers head towards the developing tooth. The nerve fibers will branch out and create a rich plexus around the tooth germ in that structure as the dental follicle is the clear target of these dental nerve fibers. The dental follicle is a fibrous sac that surrounds the odontogenic organ and developing tooth. The plexus is a system of connections of blood vessels, nerves, or lymphatic vessels.
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Recent studies show that septate junctions are also identified in the myelinated nerve fibers of the vertebrates.
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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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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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The parasympathetic root of ciliary ganglion provides parasympathetic supply to the ciliary ganglion. The ciliary ganglion is a parasympathetic ganglion. Incoming parasympathetic nerve fibers form synapses with the dendrites of nerve cells within the ganglion. However, the ciliary ganglion is not simply a relay station connecting preganglionic to postganglionic nerve fibers.
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Warm and cold sensitive nerve fibers differ in structure and function. The cold-sensitive and warm-sensitive nerve fibers are underneath the skin surface. Terminals of each temperature-sensitive fiber do not branch away to different organs in the body. They form a small sensitive point which are unique from neighboring fibers.
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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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Nerve fibers are cell processes Nerve fibers are outgrowths of nerve cells. Cell division Nerve cells are generated by cell division. Contact Nerve cells are connected by sites of contact and not cytoplasmic continuity. Waldeyer himself was neutral on this point, and strictly speaking the neuron doctrine does not depend upon this element.
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Some of these sensations may be referred to as spiciness, pungency, or piquancy. Chemesthetic sensations sometimes arise by direct chemical activation of ion channels on sensory nerve fibers, for example of transient receptor potential channels including those of the TRPV, TRPA or TRPM subtypes. Alternatively, irritant chemicals may activate cells of the epithelium to release substances that indirectly activate the nerve fibers. The respiratory passages, including the nose and trachea, possess specialized cells called solitary chemosensory cells which release acetylcholine or other activators to excite nearby nerve fibers.
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Damage or injury to nerve fibers causes neuropathic pain. Capsaicin activates C fibre vanilloid receptors, giving chili peppers a hot sensation.
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The SCN stimulates the release of Norepinephrine from sympathetic nerve fibers from the superior cervical ganglia that synapse with the pinealocytes. Norepinephrine causes the production of melatonin in the pinealocytes by stimulating the production of cAMP. Because the release of norepinephrine from the nerve fibers occurs at night, this system of regulation maintains the body’s circadian rhythms.
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The plexus of Raschkow is a network of nerves immediately beneath the odonblast layer of the dentine, first described by J. Raschkow in 1835. However, the nerve fibers will only begin entering the dental papilla (pulp) when Dentinogenesis starts. The timing is not similar to the establishment of the neural supply and the papillary vascular supply even though a feasible relationship has been assumed between the developing nerve and blood supplies. Furthermore, histo-chemistry studies have shown that in the makeup of pioneer nerve fibers heading towards the tooth germ, automatic nerve fibers are not present.
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The myelin sheaths of oligodendrocytes do not have neurilemma because excess cytoplasm is directed centrally toward the oligodendrocyte cell body. Neurilemma serves a protective function for peripheral nerve fibers. Damaged nerve fibers may regenerate if the cell body is not damaged and the neurilemma remains intact. The neurilemma forms a regeneration tube through which the growing axon re-establishes its original connection.
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Olfactory nerve fibers, which originate in the epithelium, pass through the cribriform plate, connecting the epithelium to the brain's limbic system at the olfactory bulbs.
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Both the peripheral process and the axon are myelinated. In humans, there are on average 30,000 nerve fibers within the cochlear nerve. The number of fibers varies significantly across species; the domestic cat, for example, has an average of 50,000 fibers. The peripheral axons of auditory nerve fibers form synaptic connections with the hair cells of the cochlea via ribbon synapses using the neurotransmitter glutamate.
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Rarely, choroidal neovascularization may develop as the juxtapapillary nerve fibers are disrupted, with subsequent subretinal hemorrhage and retinal scarring. Even more rarely, vitreous hemorrhage may develop.
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Group C nerve fibers are one of three classes of nerve fiber in the central nervous system (CNS) and peripheral nervous system (PNS). The C group fibers are unmyelinated and have a small diameter and low conduction velocity, whereas Groups A and B are myelinated. Group C fibers include postganglionic fibers in the autonomic nervous system (ANS), and nerve fibers at the dorsal roots (IV fiber). These fibers carry sensory information.
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The strange behavior of tonic pupils was first explained by Irene Loewenfeld in 1979. The ciliary ganglion contain many more nerve fibers directed to the ciliary muscle than nerve fibers directed to the constrictor pupillae – roughly twenty times more. The ciliary muscle is also more massive than the constrictor pupillae, again by a factor of twenty. Based on these observations, Loewenfeld proposed an explanation of the tonic pupil.
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At high sounds levels, nerve fibers whose characteristic frequencies do not exactly match the stimulus still respond, because of the motion induced in larger areas of the basilar membrane by loud sounds. Temporal theory can help explain how we maintain this discrimination. Even when a larger group of nerve fibers are all firing, there is a periodicity to this firing, which corresponds to the periodicity of the stimulus.
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White matter is the tissue through which messages pass between different areas of grey matter within the central nervous system. The white matter is white because of the fatty substance (myelin) that surrounds the nerve fibers (axons). This myelin is found in almost all long nerve fibers, and acts as an electrical insulation. This is important because it allows the messages to pass quickly from place to place.
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In addition to blocking nerves which carry pain, local anesthetics may block other types of nerve. Depending on the drug and dose, the effects may last only a few minutes or up to several hours. Sensory nerve fibers are more sensitive to the effects of the local anesthetics than motor nerve fibers. As such, an epidural can provide pain control without as much of an effect on muscle strength.
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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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Joints of the human body The joints may be classified anatomically into the following groups: # Joints of hand # Elbow joints # Wrist joints # Axillary articulations # Sternoclavicular joints # Vertebral articulations # Temporomandibular joints # Sacroiliac joints # Hip joints # Knee joints # Articulations of foot Unmyelinated nerve fibers are abundant in joint capsules and ligaments as well as in the outer part of intraarticular menisci. These nerve fibers are responsible for pain perception when a joint is strained.
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He was the chairman of General Anatomy at the Collège de France in 1875. His refined histological techniques and his work on both injured and normal nerve fibers became world-renowned. His observations on fiber nodes and the degeneration and regeneration of cut fibers had a great influence on Parisian neurology at the Salpêtrière. Soon afterwards, he discovered gaps in sheaths of nerve fibers, which were later called the Nodes of Ranvier.
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Neurolysis is the application of physical or chemical agents to a nerve in order to cause a temporary degeneration of targeted nerve fibers. When the nerve fibers degenerate, it causes an interruption in the transmission of nerve signals. In the medical field, this is most commonly and advantageously used to alleviate pain in cancer patients. The different types of neurolysis include celiac plexus neurolysis, endoscopic ultrasound guided neurolysis, and lumbar sympathetic neurolysis.
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The unmyelinated Group C nerve fibers that transmit pain and temperature from the pelvic viscera enter the spinal cord via ventral roots at L5-S3, thus violating the Bell–Magendie law.
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The discoid nerve ending can also be seen to contain clear vesicles and some dense-core vesicles. Thinner nerve fibers lacking myelin sheaths can also be observed just outside the capsule.
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The nasal mucosa in the nasal cavity is also supplied by the autonomic nervous system. Postganglionic nerve fibers from the deep petrosal nerve join with preganglionic nerve fibers from the greater petrosal nerve to form the nerve of the pterygoid canal. Sympathetic postganglionic fibers are distributed to the blood vessels of the nose. Postganglionic parasympathetic fibres derived from the pterygopalatine ganglion provide the secretomotor supply to the nasal mucous glands, and are distributed via branches of the maxillary nerves.
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The nerve fibers forming the optic nerve exit the eye posteriorly through a hole in the sclera that is occupied by a mesh-like structure called the lamina cribrosa. It is formed by a multilayered network of collagen fibers that insert into the scleral canal wall. The nerve fibers that comprise the optic nerve run through pores formed by these collagen beams. In humans, a central retinal artery is located slightly off-center in nasal direction.
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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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Cancer pain can be caused by pressure on, or chemical stimulation of, specialised pain-signalling nerve endings called nociceptors (nociceptive pain), or by damage or illness affecting nerve fibers themselves (neuropathic pain).
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In addition, the spindle also has a motor efferent innervation carried by the efferent nerve fibers of gamma motor neurons, which is used by the nervous system to modify the spindle's sensitivity.
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This results in a "bundle"-like structure of nerve fibers that extends caudally from the end of the spinal cord, gradually declining in number further down as individual pairs leave the spinal column.
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Unmyelinated nerve fibers for itch and pain both originate in the skin; however, information for them is conveyed centrally in two distinct systems that both use the same nerve bundle and spinothalamic tract.
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Although smooth muscle contractions are myogenic, the rate and strength of their contractions can be modulated by the autonomic nervous system. Postganglionic nerve fibers of parasympathetic nervous system release the neurotransmitter acetylcholine, which binds to muscarinic acetylcholine receptors (mAChRs) on smooth muscle cells. These receptors are metabotropic, or G-protein coupled receptors that initiate a second messenger cascade. Conversely, postganglionic nerve fibers of the sympathetic nervous system release the neurotransmitters epinephrine and norepinephrine, which bind to adrenergic receptors that are also metabotropic.
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When an injury occurs to the tendon, cells from surrounding structures migrate into the tendon to assist in repair. Some of these cells come from blood vessels that enter the tendon to provide direct blood flow to increase healing. With the blood vessels come nerve fibers. Researchers including Alfredson and his team in Sweden believe these nerve fibers to be the cause of the pain - they injected local anaesthetic around the vessels and this decreased significantly the pain from the Achilles tendon.
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This has been shown in guinea pig and cat models. In 1980, Don Johnson experimentally revealed phase-locking in the auditory nerve fibers of the adult cat. In the presence of -40 to -100 decibel single tones lasting 15 or 30 seconds, recordings from the auditory nerve fibers showed firing fluctuations in synchrony with the stimulus. Johnson observed that during frequencies below 1000 Hz, two peaks are recorded for every cycle of the stimulus, which had varying phases according to stimulation frequency.
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These cells envelop nerve fibers of the PNS by winding repeatedly around them. This process creates a myelin sheath, which not only aids in conductivity but also assists in the regeneration of damaged fibers.
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An individual nerve consists of a number of parallel fascicles, i.e. bundles of nerve fibers enclosed within a connective tissue sheath that may be quite tough and hard for a needle microelectrode to penetrate.
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Small clots (microthrombi) form and can cut off blood to the affected area (known as ischemia) and damage nerve fibers. Rewarming causes a series of inflammatory chemicals such as prostaglandins to increase localized clotting.
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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 sympathetic trunks (sympathetic chain, gangliated cord) are a paired bundle of nerve fibers that run from the base of the skull to the coccyx. They are a major component of the sympathetic nervous system.
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Furthermore, QST is limited by a patient's subjective experience of pain sensation. Quantitative sudomotor axon reflex testing (QSART) measures sweating response at local body sites to evaluate the small nerve fibers that innervate sweat glands.
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This selectivity to certain frequencies can be illustrated by neural tuning curves. These demonstrate the frequencies a fiber responds to, by showing threshold levels (dB SPL) of auditory nerve fibers as a function of different frequencies. This demonstrates that auditory nerve fibers respond best, and hence have better thresholds at the fiber's characteristic frequency and frequencies immediately surrounding it. The basilar membrane is said to be ‘sharply tuned’ due to the sharp ‘V’ shaped curve, with its ‘tip’ centered at the auditory fibers characteristic frequency.
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Under persistent activation, the transmission of pain signals to the dorsal horn may produce a pain wind-up phenomenon. This triggers changes that lower the threshold for pain signals to be transmitted. In addition, it may cause nonnociceptive nerve fibers to respond to, generate and transmit pain signals. The type of nerve fibers that are believed to generate the pain signals are the C-fibers, since they have a slow conductivity and give rise to a painful sensation that persists over a long time.
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The DCN has 2 nuclei. DCN also receives info from VCN. Fusiform cells integrate information to determine spectral cues to locations (for example, whether a sound originated from in front or behind). Cochlear nerve fibers (30,000+) each have a most sensitive frequency and respond over a wide range of levels. Simplified, nerve fibers’ signals are transported by bushy cells to the binaural areas in the olivary complex, while signal peaks and valleys are noted by stellate cells, and signal timing is extracted by octopus cells.
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The ethmoidal air cells receive sensory fibers from the anterior and posterior ethmoidal nerves, and the orbital branches of the pterygopalatine ganglion, which carry the postganglionic parasympathetic nerve fibers for mucous secretion from the facial nerve.
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In the peripheral nervous system (PNS), a cluster of cell bodies of neurons (homologous to a CNS nucleus) is called a ganglion. The fascicles of nerve fibers in the PNS (homologous to CNS tracts) are called nerves.
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The utricle and saccule are specialized organs present in the inner ears of all vertebrate animals. They contain otoliths (or otoconia), calcium carbonate stones, which are deposited on a gelatinous membrane that lies over the sensory hair cells. The pull that gravity exerts on the otoliths is sensed by the hair cells, and information about the gravitational stimulus is transmitted to the brain via connecting nerve fibers. The experiment was designed to determine whether otolith production and development of otolith- associated receptor cells and nerve fibers may be altered in the microgravity environment of space.
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Ephaptic coupling is a form of communication within the nervous system and is distinct from direct communication systems like electrical synapses and chemical synapses. It may refer to the coupling of adjacent (touching) nerve fibers caused by the exchange of ions between the cells, or it may refer to coupling of nerve fibers as a result of local electric fields.Aur D., Jog, MS. (2010) Neuroelectrodynamics: Understanding the brain language, IOS Press, In either case ephaptic coupling can influence the synchronization and timing of action potential firing in neurons. Myelination is thought to inhibit ephaptic interactions.
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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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The effects of cooling vests on athletes to improve their performance has been evaluated on several occasions; at the 2004 Summer Olympics several Americans and Australians were fitted with cooling vests supplied by Nike and Arctic Heat 2004,2008,2012,2016 Olympics, used prior to their events. Cooling vests are also used by persons with multiple sclerosis. In multiple sclerosis, nerve fibers become demyelinated which leads to pain and discomfort when temperature is elevated. Nerve fibers may also be remyelinating or in the process of repairing themselves and still be sensitive to elevated temperatures.
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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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Because it is innervated by preganglionic nerve fibers, the adrenal medulla can be considered as a specialized sympathetic ganglion. Unlike other sympathetic ganglia, however, the adrenal medulla lacks distinct synapses and releases its secretions directly into the blood.
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In the autonomic nervous system there are both sympathetic and parasympathetic ganglia which contain the cell bodies of postganglionic sympathetic and parasympathetic neurons respectively. A pseudoganglion looks like a ganglion, but only has nerve fibers and has no nerve cell bodies.
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Some theories have been that women have smaller, more breakable nerve fibers in their brains, that their necks are weaker and so their brains accelerate more sharply on impact, or fluctuating hormones during menstrual cycles that make them more susceptible.
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One prominent practitioner, Bernard Jensen, described it thus: "Nerve fibers in the iris respond to changes in body tissues by manifesting a reflex physiology that corresponds to specific tissue changes and locations."Jensen B; "Iridology Simplified". 2nd ed., Escondido 1980.
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This particular sensation, called chemesthesis, is not a taste in the technical sense, because the sensation does not arise from taste buds, and a different set of nerve fibers carry it to the brain. Foods like chili peppers activate nerve fibers directly; the sensation interpreted as "hot" results from the stimulation of somatosensory (pain/temperature) fibers on the tongue. Many parts of the body with exposed membranes but no taste sensors (such as the nasal cavity, under the fingernails, surface of the eye or a wound) produce a similar sensation of heat when exposed to hotness agents.
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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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The terms "Tarlov cyst" or "sacral perineural cyst" refer to cystic lesions of the spinal meninges with innervation as well as nerve sheath dilatations with subarchnoid communication. While they were once thought to be a histopathological finding, they can be radiologically confirmed by specialized time lapsed MRI and CT imaging techniques showing subarchnoid communication from the nerve fibers in the cysts. They can also be surgically verified when the nerve fibers are visualized in the cystic sac. Often the cysts cause erosion from enlargement, damaging vertebrae and discs and can be misdiagnosed as primary stenosis or disc herniation.
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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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A pseudoganglion is a localized thickening of the main part or trunk of a nerve that has the appearance of a ganglion but has only nerve fibers and no nerve cell bodies. Pseudoganglia are found in the teres minor muscle and radial nerve.
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ACh is secreted by parasympathetic nerve fibers of both the short and long reflex ,.ml; pathways. Histamine is a paracrine secretion from the enteroendocrine cells in the gastric glands. Gastrin is a hormone produced by enteroendocrine G cells in the pyloric glands.
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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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Corpus Callosum is a 2007 film by Sarah Nagy and Bryan Felber. It debuted in the United States on December 13, 2007. It is named after the corpus callosum, a bundle of nerve fibers connecting the left and right hemispheres of the brain.
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There may be considerable pain and cramping. Regenerating nerve fibers may create shooting pains. Patients may have hot or cold sensations and may feel worse than before surgery. Crutches are usually recommended for the first two weeks, as well as elevation to minimize swelling.
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Small fiber peripheral neuropathy is a type of peripheral neuropathy that occurs from damage to the small unmyelinated peripheral nerve fibers. These fibers, categorized as C fibers and small Aδ fibers, are present in skin, peripheral nerves, and organs.Overview of Small Fiber Neuropathy. Therapath Neuropathology.
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Heath, in the 1950s, stimulated subcortical areas and made detailed observations of behavioral changes. A new understanding of pain perception was ushered in in 1965, with the Gate Theory of Wall and Melzack. Although now considered oversimplified, the theory held that pain transmissions from small nerve fibers can be overridden, or the gate "closed", by competing transmissions along the wider touch nerve fibers. Building on that concept, in 1967, the first dorsal column stimulator for pain control was demonstrated by Dr. Norm Shealy at Western Reserve Medical School, using a design adapted by Tom Mortimer, a graduate student at Case Institute of Technology, from cardiac nerve stimulators by Medtronic, Inc.
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342x342px The sympathoadrenal system is a physiological connection between the sympathetic nervous system and the adrenal medulla and is crucial in an organism's physiological response to outside stimuli. When the body receives sensory information, the sympathetic nervous system sends a signal to preganglionic nerve fibers, which activate the adrenal medulla through acetylcholine. Once activated, norepinephrine and epinephrine are released directly into the blood by postganglionic nerve fibers where they act as the bodily mechanism for "fight-or-flight" responses. Because of this, the sympathoadrenal system plays a large role in maintaining glucose levels, sodium levels, blood pressure, and various other metabolic pathways that couple with bodily responses to the environment.
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The pharyngeal plexus is a network of nerve fibers innervating most of the palate and pharynx. (Larynx, which is innervated by superior and recurrent laryngeal nerve from vagus nerve (CN X), is not included) It is located on the surface of the middle pharyngeal constrictor muscle.
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Handbook of Clinical Neurology. p. 37. In press. It is often associated with endocrinopathies (hormone deficiencies), developmental delay, and brain malformations. The optic nerve, which is responsible for transmitting visual signals from the retina to the brain, has approximately 1.2 million nerve fibers in the average person.
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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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The northern leopard frog has been a preferred species for making discoveries about basic properties of neurons since the 1950s. The neuromuscular junction of the sciatic nerve fibers of the sartorius muscle of this frog has been the source of initial data about the nervous system.
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Like phospholipids, these fatty acid derivatives have a polar head and nonpolar tails. Unlike phospholipids, sphingolipids have a sphingosine backbone. Sphingolipids exist in eukaryotic cells and are particularly abundant in the central nervous system. For example, sphingomyelin is part of the myelin sheath of nerve fibers.
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Mechanism of nociceptive pain. Nociceptive pain is caused by stimulation of sensory nerve fibers that respond to stimuli approaching or exceeding harmful intensity (nociceptors), and may be classified according to the mode of noxious stimulation. The most common categories are "thermal" (e.g. heat or cold), "mechanical" (e.g.
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Alpha motor neurons target extrafusal muscle fibers. The motor nerves associated with these neurons innervate extrafusal skeletal muscle fibers and are responsible for muscle contraction. These nerve fibers have the largest diameter of the motor neurons and require the highest conduction velocity of the three types.
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The esophageal plexus (oesophageal plexus in British-English) is formed by nerve fibers from two sources, branches of the vagus nerve and visceral branches of the sympathetic trunk. The esophageal plexus and the cardiac plexus contain the same types of fibers and are both considered thoracic autonomic plexus.
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The dorsal cochlear nucleus (DCN, also known as the "tuberculum acusticum"), is a cortex-like structure on the dorso-lateral surface of the brainstem. Along with the ventral cochlear nucleus (VCN), it forms the cochlear nucleus (CN), where all auditory nerve fibers from the cochlea form their first synapses.
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Herbert Spencer Gasser (July 5, 1888 – May 11, 1963) was an American physiologist, and recipient of the Nobel Prize for Physiology or Medicine in 1944 for his work with action potentials in nerve fibers while on the faculty of Washington University in St. Louis, awarded jointly with Joseph Erlanger.
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Nerve fibers extend into the snake epidermis and anchor near scales, generally at the rostral, or head, end of the snake. Specifically, nerves anchor to sensory spines and pits, which are touch and thermal detection organs, respectively. The hypodermis is below the dermis. This layer mainly stores fat.
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When there is damage to the nerve that innervates the throat, the vagus nerve, both motor and sensory function can be affected since the vagus contains both motor and sensory nerve fibers. However, until sensory testing was developed there was no way to assess sensory loss from a vagus nerve injury. One of the most common symptoms of a vagus nerve injury is chronic cough. If a physician looked into the vocal cords of a patient with chronic cough it would appear they are opening and closing normally, however if sensory testing was performed it would give abnormal results thus indicating that the sensory nerve fibers of the vagus were somehow damaged.
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The normal function of the sympathoadrenal system is to help the body regulate responses to environmental stimuli. These stimuli travel through the sympathetic nervous system by means of preganglionic nerve fibers that emerge from the thoracic spinal chord. Electrical impulses carried by the sympathetic nervous system are converted to a chemical response in the adrenal gland. Chromaffin cells contained in the adrenal medulla act as postganglionic nerve fibers that release this chemical response into the blood as circulating messenger. The sympathoadrenal system can activate and discharge chemical messengers as a single unit to activate an organism's “fight or flight” response. This “sympathoadrenal discharge” causes an increase in heart rate, cardiac output, blood pressure, and glucose levels.
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These cells are modified postganglionic neurons. Autonomic nerve fibers lead directly to them from the central nervous system. The adrenal medullary hormones are kept in vesicles much in the same way neurotransmitters are kept in neuronal vesicles. Hormonal effects can last up to ten times longer than those of neurotransmitters.
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Skeletal muscle includes skeletal muscle fibers, blood vessels, nerve fibers, and connective tissue. Skeletal muscle is wrapped in epimysium, allowing structural integrity of the muscle despite contractions. The perimysium organizes the muscle fibers, which are encased in collagen and endomysium, into fascicles. Each muscle fiber contains sarcolemma, sarcoplasm, and sarcoplasmic reticulum.
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It explains the defining features of a tonic pupil: :(1) The pupil does not react to light. The original light-reaction neurons have been destroyed. :(2) Tonic constriction with attempted near vision. Aberrant regeneration of nerve fibers intended for the ciliary muscle causes abnormal, tonic contraction of the pupil with accommodation.
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1605941113 in air pollution.Nano air pollutants strike a blow to the brain, Alison Pearce Stevens, Science News for Students, December 17, 2014 In naegleriasis, "brain-eating" amoeba enter through the olfactory mucosa of the nasal tissues and follow the olfactory nerve fibers into the olfactory bulbs and then the brain.
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Some of them have an apical tuft of rigid microvilli (brush cells). Other elements have secretory exocrine granules and others may have endocrine differentiation. Often these elements are innervated. In the upper respiratory system the SCCs are contacted by the sensory endings of trigeminal nerve fibers (SubP and CGRP immunoreactive).
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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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Lateral propriospinal tract is a collection of nerve fibers, ascending, descending, crossed and uncrossed, that interconnect various levels of the spinal cord. Its fibers are largely myelinated. It is a component of the white lateral columns. Most prominent in the cervical and lumbar regions, it is located close to the spinal central gray.
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The dorsal propriospinal tract is a collection of nerve fibers, ascending, descending, crossed and uncrossed, that interconnect various levels of the spinal cord. It is a component of the white posterior column. Myelinated fibers are located adjacent to the spinal central gray. Shorter fibers are closer to, longer fibers further from the gray.
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Exercise has been shown to contribute to spikes in pressure as well. When the pressure is great enough to cause damage to the optic nerve, this is called pigmentary glaucoma. As with all types of glaucoma, when damage happens to the optic nerve fibers, the vision loss that occurs is irreversible and painless.
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In various tissues, such as the skin, the release of bioactive tachykinins by sensory nerve fibers C, that extend from the dorsal root ganglia into the epidermis, directly influence the activity of keratinocytes. Inflammation, tissue healing and cell proliferation have been linked to both SP and neurokinin A release into surrounding tissues.
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This represents total degradation of the facial nerve. Lastly, axonotmesis consists of damage to the inner nerve fibers while the outer covering remains whole, and also yields a flat line in response to stimulation. Because of their similar recordings, electroneuronography cannot, by itself, distinguish between the latter two forms of nerve injury.
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The optic nerve contains axons of nerve cells that emerge from the retina, leave the eye at the optic disc, and go to the visual cortex where input from the eye is processed into vision. There are 1.2 million optic nerve fibers that derive from the retinal ganglion cells of the inner retina.
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He concluded that his observations showed how different sound wave frequencies are locally dispersed before exciting different nerve fibers that lead from the cochlea to the brain. In 1961, he was awarded the Nobel Prize in Physiology or Medicine for his research on the function of the cochlea in the mammalian hearing organ.
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In a sympathectomy, a sympathetic ganglion is surgically removed to treat hyperhidrosis, or excessive sweating. In a vagotomy, the vagus nerve is surgically removed to treat peptic ulcer disease through reducing stomach acid. In a rhizotomy, nerve fibers in the spinal cord are removed in the hopes of eliminating chronic muscle pain.
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Biology, p. 669\. McGraw-Hill Education, New York. . The brain is protected in a cartilaginous cranium. The giant nerve fibers of the cephalopod mantle have been widely used for many years as experimental material in neurophysiology; their large diameter (due to lack of myelination) makes them relatively easy to study compared with other animals.
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Nerve fibers of various kinds are more or less randomly mixed in most nerves. This is true for fibers of different functions as well as fibers of different size. Basically fiber diameter is closely related to function, e.g. cutaneous pain system is dependent on small fibers whereas discriminative touch is dependent on large fibers.
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The method was used to study action potentials in nerve fibers. Huxley observed Stämpfli's method and agreed that it was useful and produced very few errors. The sucrose gap technique also contributed to Stämpfli's and Huxley's discovery of inhibitory junction potentials. Since its introduction, many improvements and alterations have been made to the technique.
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Nerve fibers, arteries, and intestines are spun on factory bobbins, while the Robots themselves are assembled like automobiles.Rieder, John "Karl Čapek" in Mark Bould (ed.) (2010) Fifty Key Figures in Science Fiction. London, Routledge. . pp. 47–51. Čapek's robots are living biological beings, but they are still assembled, as opposed to grown or born.
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Saltatory conduction occurs widely in the myelinated nerve fibers of vertebrates, but was later discovered in a pair of medial myelinated giant fibers of Fenneropenaeus chinensis and Marsupenaeus japonicus shrimp, as well as in a median giant fiber of an earthworm. Saltatory conduction has also been found in the small- and medium-sized myelinated fibers of Penaeus shrimp.
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Facet joints also prevent each vertebra from slipping over the one below. A small capsule surrounds each facet joint providing a nourishing lubricant for the joint. Also, each joint has a rich supply of tiny nerve fibers that provide a painful stimulus when the joint is injured or irritated. Inflamed facets can cause a powerful muscle spasm.
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In some forms of neuropathy the topical application of local anesthetics such as lidocaine may provide relief. A transdermal patch containing lidocaine is available commercially in some countries. Repeated topical applications of capsaicin are followed by a prolonged period of reduced skin sensibility referred to as desensitization, or nociceptor inactivation. Capsaicin causes reversible degeneration of epidermal nerve fibers.
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The activation of AANAT leads to an increase in melatonin production. Though there are some differences specific to certain species of vertebrates, the effect of cAMP on AANAT and AANAT on melatonin synthesis remains fairly consistent. Melatonin synthesis is also regulated by the nervous system. Nerve fibers in the retinohypothalamic tract connect the retina to the suprachiasmatic nucleus (SCN).
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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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Researches in 2005 and 2010 found that tanycytes participate in the release of gonadotropin-releasing hormone (GnRH). GnRH is released by neurons located in the rostral hypothalamus. These nerve fibers are concentrated in the region that exactly matches the distribution of β1 tanycytes. β1 and β2 tanycytes are found nearer the arcuate nucleus and the median eminence.
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GHK promotes nerve regeneration. Axon regeneration was studied using collagen tubes with incorporated peptides. GHK increased migration of hematogenous cells into collagen tube, production of nerve growth factors, expression of integrins and the rate of regeneration of myelinated nerve fibers. In addition, GHK also increased axon count and proliferation of Schwann cells compared to the control.
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Tiger conch (C. luhuanus) In gastropod eye regeneration, the degenerating nerve is important for the formation of the new eye. New axons leave the eye cup and bundle together to form the optic nerve. The new nerve fibers seem to be attracted to the previous optic nerve, and grow down it until they make contact with the cerebral ganglion.
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The posterior interosseous nerve (or dorsal interosseous nerve) is a nerve in the forearm. It is the continuation of the deep branch of the radial nerve, after this has crossed the supinator muscle. It is considerably diminished in size compared to the deep branch of the radial nerve. The nerve fibers originate from cervical segments C7 and C8.
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Vestibulectomy, during which the nerve fibers to the area are cut out, may be recommended if other treatments have not been found to be effective. There have been no high quality studies looking at surgery as a treatment. While improvement has been noted in 60% to 90%, those who were treated without surgery improved in 40–80% of cases.
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The anterior optic nerve receives blood primarily from the posterior ciliary arteries. The anterior optic nerve, a.k.a. the optic nerve head, is surrounded by the scleral canal, and is vulnerable to crowding of nerve fibers. The portion of the optic nerve head that is visible by looking into the eye with an ophthalmoscope is called the optic disc.
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A nuclear bag fiber is a type of intrafusal muscle fiber that lies in the center of a muscle spindle. Each has many nuclei concentrated in bags and they cause excitation of both the primary and secondary nerve fibers. There are two kinds of bag fibers based upon contraction speed and motor innervation. #BAG2 fibers are the largest.
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The neuronal encoding of sound is the representation of auditory sensation and perception in the nervous system. This article explores the basic physiological principles of sound perception, and traces hearing mechanisms from sound as pressure waves in air to the transduction of these waves into electrical impulses (action potentials) along auditory nerve fibers, and further processing in the brain.
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Based upon the data presented in In addition to inhibiting neural excitability, it has been observed that preceding an electrical stimulus with a depolarizing prepulse allows one to invert the current-distance relationship controlling nerve fiber recruitment, where the current-distance relationship describes how the threshold current for nerve fiber excitation is proportional to the square of the distance between the nerve fiber and the electrode. Therefore, if the region of influence for the depolarizing prepulse is less than that for the stimulus, the nerve fibers closer to the electrode will experience a greater increase in their threshold current for excitation. Thus, provided such a stimulus, the nerve fibers closest to the electrode may be inhibited, while those further away may be excited. A simulation of this stimulation, constructed by Drs.
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The retina, a specialised type of tissue containing photoreceptors, senses light. These specialised cells convert light into electrochemical signals. These signals travel along the optic nerve fibers to the brain, where they are interpreted as vision in the visual cortex. Primates and many other vertebrates use three types of voluntary eye movement to track objects of interest: smooth pursuit, vergence shifts and saccades.
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Pain wind-up is the increase in pain intensity over time when a given stimulus is delivered repeatedly above a critical rate. It is caused by repeated stimulation of group C peripheral nerve fibers, leading to progressively increasing electrical response in the corresponding spinal cord (posterior horn) neurons due to priming of the NMDA receptor based response.Pitcher and Henry (2000). Eur. J. Neurosci.
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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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Ventral propriospinal tract is a collection of nerve fibers, ascending, descending, crossed and uncrossed, that interconnect various levels of the spinal cord. It is a component of the white anterior columns. The fibers are largely myelinated and run close to the spinal central gray for the length of the cord. Shorter fibers are closer to, longer fibers further from the gray.
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Olfactory receptor neuron axons project through the cribriform plate to the olfactory bulb. The olfactory bulb is a structure at the base of the frontal lobe. It comprises neurons, nerve fibers, interneurons, microglia, astrocytes, and blood vessels. It is made up of 6 layers: olfactory nerve layer, glomerular layer, external plexiform layer, mitral cell layer, internal plexiform layer, and granule layer.
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The Central Nervous System controls most of the functions of the body and mind. It comprises the brain, spinal cord and the nerve fibers that branch off to all parts of the body. The Central Nervous System viral diseases are caused by viruses that attack the CNS. Existing and emerging viral CNS infections are major sources of human morbidity and mortality.
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Drugs with Anticholinergic Activity. Prescriber's Letter 2011; 18 (12):271233. These agents inhibit the parasympathetic nervous system by selectively blocking the binding of ACh to its receptor in nerve cells. The nerve fibers of the parasympathetic system are responsible for the involuntary movement of smooth muscles present in the gastrointestinal tract, urinary tract, lungs, and many other parts of the body.
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Bielschowsky silver stain showing the processes of basket cells in the cerebellum. The Bielschowsky technique is a silver staining method used in histochemistry for the visualization of nerve fibers, including multipolar interneurons in the cerebellum. The method is attributed to German neurologist and neurohistologist Max Bielschowsky (1869–1940), who made improvements over the previous method developed by Ramon y Cajal (1852–1934).
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Inside the subarachnoid, bacteria replicate and cause inflammation from released toxins such as hydrogen peroxide (H2O2) . These toxins have been found to damage the mitochondria and produce a large scale immune response. Headache and meningismus are often signs of inflammation relayed via trigeminal sensory nerve fibers within the pia mater. Disabling neuropsychological effects are seen in up to half of bacterial meningitis survivors.
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Superior alternating hemiplegia (also known as Weber syndrome) has a few distinct symptoms: contralateral hemiparesis of limb and facial muscle accompanied by weakness in one or more muscles that control eye movement on the same side. Another symptom that appears is the loss of eye movement due to damage to the oculomotor nerve fibers. The upper and lower extremities have increased weakness.
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Cervical spinal nerve 4, also called C4, is a spinal nerve of the cervical segment. It originates from the spinal cord above the 4th cervical vertebra (C4). It contributes nerve fibers to the phrenic nerve, the motor nerve to the thoracoabdominal diaphragm. It also provides motor nerves for the longus capitis, longus colli, anterior scalene, middle scalene, and levator scapulae muscles.
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The adrenal medulla consists of irregularly shaped cells grouped around blood vessels. These cells are intimately connected with the sympathetic division of the autonomic nervous system (ANS). In fact, these adrenal medullary cells are modified postganglionic neurons, and preganglionic autonomic nerve fibers lead to them directly from the central nervous system. The adrenal medulla therefore affects available energy, heart rate, and metabolism.
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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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Structural changes are observed in the cortex, which controls higher functions, sensation, muscle movements, and memory. Structural defects are seen in the cerebellum too, which affect the motor and communication skills. Sometimes the left lobe of the brain is affected and this causes neuropsychological symptoms. The distribution of white matter, the nerve fibers that link diverse parts of the brain, is abnormal.
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This study focused on how the eye processes information it receives despite having so many overlapping nerve fibers and networks. The extracellular action potentials are measured giving an idea as to the arrangement of the ganglion cells, which was followed by the measure of the voltage of the signals. In addition, this study utilized visual methods to characterize a neuron's response to stimuli.
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In some cases - approximately 20% of the population - there is a branch of the ciliary circulation called the cilio-retinal artery which supplies the retina between the macula and the optic nerve, including the nerve fibers from the foveal photoreceptors. If this artery is present, the central vision will be preserved even in case of central retinal artery occlusion (CRAO).
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The central retinal artery supplies blood to all the nerve fibers that form the optic nerve, which carries the visual information to the lateral geniculate nucleus of the thalamus, including those that reach over the fovea. Its blood flow can be revealed by fluorescein angiography or laser Doppler imaging.Puyo, L., M. Paques, M. Fink, J-A. Sahel, and M. Atlan.
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Local anesthetic agents prevent transmission of nerve impulses without causing unconsciousness. They act by reversibly binding to fast sodium channels from within nerve fibers, thereby preventing sodium from entering the fibres, stabilising the cell membrane and preventing action potential propagation. Each of the local anesthetics have the suffix "–caine" in their names. Local anesthetics can be either ester- or amide-based.
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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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Schabadasch A (1930) Untersuchungen zur Methodik der Methylenblaufarbung des vegetativen Nervensystems. Zeitschrift für Zellforschung 10: 221-243.Zacks Zacks SI (1973) The Motor Endplate, 2nd ed. Huntington, NY: Krieger The mechanism of selective dye uptake is incompletely understood; vital staining of nerve fibers in skin is prevented by ouabain, a drug that inhibits the Na/K-ATPase of cell membranes.
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Nociception (also nocioception, from Latin nocere 'to harm or hurt') is the sensory nervous system's process of encoding noxious stimuli. In nociception, intense chemical (e.g., cayenne powder), mechanical (e.g., cutting, crushing), or thermal (heat and cold) stimulation of sensory nerve cells called nociceptors produces a signal that travels along a chain of nerve fibers via the spinal cord to the brain.
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Each spinal nerve receives a branch called a gray ramus communicans (plural rami communicantes) from the adjacent paravertebral ganglion of the sympathetic trunk. The gray rami communicantes contain postganglionic nerve fibers of the sympathetic nervous system and are composed of largely unmyelinated neurons. This is in contrast to the white rami communicantes, in which heavily myelinated neurons give the rami their white appearance.
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Increases in the strength-duration time constant are observed when this conductance is activated by depolarization, or by hyperventilation. However, demyelination, which exposes internodal membrane with a higher membrane time constant than that of the original node, can also increase strength-duration time constant.Bostock, H., et al. (1983) "The spatial distribution of excitability and membrane current in normal and demyelinated mammalian nerve fibers".
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The diagnosis of small fiber neuropathy often requires ancillary testing. Nerve conduction studies and electromyography are commonly used to evaluate large myelinated sensory and motor nerve fibers, but are ineffective in diagnosing small fiber neuropathies. Quantitative sensory testing (QST) assesses small fiber function by measuring temperature and vibratory sensation. Abnormal QST results can be attributed to dysfunction in the central nervous system.
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The posterior commissure is at the top of the photo, and the space below the SCO is part of the third ventricle, which is lined with ependymal cells. Cell nuclei are stained blue. The scale bar = 50 microns (0.05 mm). The name of the SCO comes from its location beneath the posterior commissure, a bundle of nerve fibers interconnecting parts of the two hemispheres of the brain.
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The neurological basis and mechanisms for phantom limb pain are all derived from experimental theories and observations. Little is known about the true mechanism causing phantom pains, and many theories highly overlap. Historically, phantom pains were thought to originate from neuromas located at the stump tip. Traumatic neuromas, or non-tumor nerve injuries, often arise from surgeries and result from the abnormal growth of injured nerve fibers.
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He utilized his prowess for electrical engineering to attempt to create artificial constructs that were able to mimic the formation and propagation of impulses along nerve fibers. This unique pursuit inadvertently caused Otto to create novel forms of electrical circuitry that are still used today. Harkness uses the example of the differential amplifier, which is a basic component in instrumentation used to record and measure biological potentials.
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However, the myelin layer does not ensure a perfect regeneration of the nerve fiber. Some regenerated nerve fibers do not find the correct muscle fibers, and some damaged motor neurons of the peripheral nervous system die without regrowth. Damage to the myelin sheath and nerve fiber is often associated with increased functional insufficiency. Unmyelinated fibers and myelinated axons of the mammalian central nervous system do not regenerate.
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The BAHA sound processor sits on this abutment and transmits sound vibrations to the external abutment of the titanium implant. The implant vibrates the skull and inner ear, which stimulate the nerve fibers of the inner ear, allowing hearing. The surgical procedure is simple both for the surgeon, involving very few risks for the experienced ear surgeon. For the patient, minimal discomfort and pain is reported.
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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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The lateral vestibulospinal tract is a group of descending extrapyramidal motor neurons, or efferent nerve fibers. This tract is found in the lateral funiculus, a bundle of nerve roots in the spinal cord. The lateral vestibulospinal tract originates in the lateral vestibular nucleus or Deiters’ nucleus in the pons. The Deiters' nucleus extends from pontomedullary junction to the level of abducens nerve nucleus in the pons.
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LSO neurons are excited by inputs from one ear and inhibited by inputs from the other, and are therefore referred to as IE neurons. Excitatory inputs are received at the LSO from spherical bushy cells of the ipsilateral cochlear nucleus, which combine inputs coming from several auditory nerve fibers. Inhibitory inputs are received at the LSO from globular bushy cells of the contralateral cochlear nucleus.
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In children, optic disc drusen are usually buried and undectectable by fundoscopy except for a mild or moderate elevation of the optic disc. With age, the overlying axons become atrophied and the drusen become exposed and more visible. They may become apparent with an ophthalmoscope and some visual field loss at the end of adolescence. ODD can compress and eventually compromise the vasculature and retinal nerve fibers.
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A neuroma (; plural: neuromata or neuromas) is a growth or tumor of nerve tissue. Neuromas tend to be benign (i.e. not cancerous); many nerve tumors, including those that are commonly malignant, are nowadays referred to by other terms. Neuromas can arise from different types of nervous tissue, including the nerve fibers and their myelin sheath, as in the case of genuine neoplasms (growths) like ganglioneuromas and neurinomas.
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Current research has focused mostly on determining treatment options. This has been studied through clinical trials with drugs listed previously or through new therapy techniques that delay loss in function. Most drugs being studied are immunosuppressants that can attack the antibodies or other aspects in the hope of preventing damage to the Schwann cells. This will, ideally, prevent the loss of myelination on peripheral nerve fibers.
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The septum pellucidum is located in the septal area in the midline of the brain between the two cerebral hemispheres. The septal area is also the location of the septal nuclei. It is attached to the lower part of the corpus callosum, the large collection of nerve fibers that connect the two cerebral hemispheres. It is attached to the front forward part of the fornix.
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Neurotomy may refer to the application of heat (as in radio frequency nerve lesioning) or freezing to sensory nerve fibers to cause their temporary degeneration, usually to relieve pain. Neurotomy and neurolysis (where the degeneration is caused by the application of chemical agents) are forms of neurolytic block. "Neurotomy" is sometimes used as a synonym for neurectomy, the surgical cutting or removal of nervous tissue.
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Sulfatide plays an important role in the myelin. Myelin acts as an insulating sheath that surrounds many nerve fibers and increases the speed at which impulses are conducted. When sulfatide is not distributed properly, it can affect the normal physiological conduction of electrical impulses between nerve cells. This then results in demyelination because of the buildup of sulfatide and is the main cause of Metachromatic Leukodystrophy.
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Myelin is a layer of a fatty insulating substance, which is formed by two types of glial cells Schwann cells and oligodendrocytes. In the peripheral nervous system Schwann cells form the myelin sheath of a myelinated axon. In the central nervous system oligodendrocytes form the insulating myelin. Along myelinated nerve fibers, gaps in the myelin sheath known as nodes of Ranvier occur at evenly spaced intervals.
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Nerves continue down the spine below this, but in a loose bundle of nerve fibers called the cauda equina. There is lower risk with inserting a needle into the spine at the level of the cauda equina because these loose fibers move out of the way of the needle without being damaged. The lumbar cistern extends into the sacrum up to the S2 vertebra.
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In the scrotum, it consists mostly of smooth muscle.Gray's 16th Edition The tone of this smooth muscle is responsible for the wrinkled (rugose) appearance of the scrotum. In females, the same muscle fibers are less well developed and termed dartos muliebris, lying beneath the skin of the labia majora. It receives innervation from postganglionic sympathetic nerve fibers arriving via the ilioinguinal nerve and the posterior scrotal nerve.
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An ophthalmoscopic view of the retina showing advanced signs of diabetic retinopathy including two pale cotton wool spots. Cotton wool spots are an abnormal finding on funduscopic exam of the retina of the eye. They appear as fluffy white patches on the retina. They are caused by damage to nerve fibers and are a result of accumulations of axoplasmic material within the nerve fiber layer.
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HSP is caused by defects in transport of proteins, structural proteins, cell maintaining proteins, lipids, and other substances through the cell. Long nerve fibers (axons) are affected because long distances make nerve cells particularly sensitive to defects in these mentioned mechanisms. The disease was first mentioned in 1876Seeligmuller A. Sklerose der Seitenstränge des Rückenmarks bei vier Kindern derselben Familie. Dtsch Med Wschr. 1876;2:185-6.
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Lera Boroditsky. (1999) "Hearing I: Lecture Notes." pp. 3 Békésy concluded from these observations that by exciting different locations on the basilar membrane different sound wave frequencies excite different nerve fibers that lead from the cochlea to the brain. He theorized that, due to its placement along the cochlea, each sensory cell (hair cell) responds maximally to a specific frequency of sound (the so-called tonotopy).
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Hair cells are columnar cells, each with a bundle of 100–200 specialized cilia at the top, for which they are named. There are two types of hair cells; inner and outer hair cells. Inner hair cells are the mechanoreceptors for hearing: they transduce the vibration of sound into electrical activity in nerve fibers, which is transmitted to the brain. Outer hair cells are a motor structure.
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The axillary nerve or the circumflex nerve is a nerve of the human body, that originates from the brachial plexus (upper trunk, posterior division, posterior cord) at the level of the axilla (armpit) and carries nerve fibers from C5 and C6. The axillary nerve travels through the quadrangular space with the posterior circumflex humeral artery and vein to innervate the deltoid and teres minor.
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Signs and symptoms vary according to the affected level of the spinal cord. The underlying cause of TM is unknown. The spinal cord inflammation seen in TM has been associated with various infections, immune system disorders, or damage to nerve fibers, by loss of myelin. As opposed to leukomyelitis which affects only the white matter, it affects the entire cross-section of the spinal cord.
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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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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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It consists of fibers that are said to arise in the parolfactory area, the gyrus subcallosus and the anterior perforated substance, and course backward in the longitudinal striae to the dentate gyrus and the hippocampal region. This is a cholinergic bundle of nerve fibers posterior to the anterior perforated substance. It interconnects the subcallosal gyrus in the septal area with the hippocampus and lateral olfactory area.
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Peak amplitudes are typically below 1 mA and do not produce phase charges strong enough to excite peripheral nerve fibers and reach the sensory threshold. Stimulators that work at this level are termed microcurrent electrical nerve stimulators (MENS). In addition to the low amplitudes, pulse durations are short, thereby activating neither the muscle nor the nerve. No studies have shown clinical effectiveness of subsensory-level stimulation.
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This glycoprotein shares molecular domains with axonal pathfinding molecules. The ependymal cells and the SCO–spondin secretion are thought to play a role in homeostasis. The ependymal cells of the SCO are also involved in the production of brain transthyretin, a protein involved in the transport of thyroid hormones in blood. Some studies indicate the presence of both tyrosine-hydroxylase-immunoreactive nerve fibers and dopamine receptors in the SCO ependyma.
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Special visceral efferent fibers (SVE) are the efferent nerve fibers that provide motor innervation to the muscles of the pharyngeal arches in humans, and the branchial arches in fish. Some sources prefer the term "branchiomotor" or "branchial efferent". The only nerves containing SVE fibers are cranial nerves: the trigeminal nerve (V), the facial nerve (VII), the glossopharyngeal nerve (IX), the vagus nerve (X) and the accessory nerve (XI).Drake et al.
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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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The juxtaoral organ in humans is a small longish structure (10–14 mm in length, 1–2 mm in diameter), situated medially to the medial pterygoid muscle. The organ consists of a central ramified cord of epithelial parenchyma, embedded in connective tissue particularly rich in nerve fibers and sensory receptors. Close relations exist between epithelial cells and nerve endings. Histochemically, the parenchyma displays a characteristic pattern of various enzymes.
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In most patients, optic disc drusen are an incidental finding. It is important to differentiate them from other conditions that present with optic disc elevation, especially papilledema, which could imply raised intracranial pressure or tumors. True papilledema may present with exudates or cotton-wool spots, unlike ODD. The optic disc margins are characteristically irregular in ODD but not blurred as there is no swelling of the retinal nerve fibers.
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Full-body or localized pain to the extremities (known as acroparesthesia) or gastrointestinal (GI) tract is common in patients with Fabry disease. This pain can increase over time. This acroparesthesia is believed to be related to the damage of peripheral nerve fibers that transmit pain. GI-tract pain is likely caused by accumulation of lipids in the small vasculature of the GI tract, which obstructs blood flow and causes pain.
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It is a disorder that is mostly characterized as developmental delay and short stature. Magnetic resonance imaging scans usually reveal that there is a decreased volume of white matter in the bilateral cerebral hemispheres, a brain stem that is smaller in size, and a thin corpus callosum (nerve fibers that connect the two hemispheres of the brain). The syndrome is one of the rare causes of short stature.
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Harrison successfully cultured frog neuroblasts in a lymph medium, proving that nerve fibers develop without a preexisting bridge or chain and that tissues can be grown outside of the body. He published the results of his studies in 1907. This part of Harrison's research was the first step toward current research on precursor and stem cells. While Harrison himself didn't develop this area of research any further, he encouraged others to.
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Menzel also found that most of the cells he studied had secondary sensitivities that corresponded to wavelength regions at which the other two receptor types were maximally active. He used spectral efficiency experiments to suggest that these secondary sensitivities result from electric coupling between the receptors. Certain morphologies distinguished the receptor types. UV cells were found to have long visual nerve fibers that penetrated the lamina with deep tree-like branchings.
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Pain evoked by the A-delta fibers is described as sharp and is felt first. This is followed by a duller pain, often described as burning, carried by the C fibers. These "first order" neurons enter the spinal cord via Lissauer's tract. These A-delta and C fibers connect with "second order" nerve fibers in the central gelatinous substance of the spinal cord (laminae II and III of the dorsal horns).
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Two roots make up the ansa cervicalis, a superior root, and an inferior root. Ansa cervicalis The superior root of the ansa cervicalis is formed from cervical spinal nerve 1 of the cervical plexus. These nerve fibers travel in the hypoglossal nerve before separating in the carotid triangle to form the superior root. The superior root goes around the occipital artery and then descends on the carotid sheath.
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SP initiates expression of almost all known immunological chemical messengers (cytokines). Also, most of the cytokines, in turn, induce SP and the NK1 receptor. SP is particularly excitatory to cell growth and multiplication, via usual, as well as oncogenic driver. SP is a trigger for nausea and emesis, Substance P and other sensory neuropeptides can be released from the peripheral terminals of sensory nerve fibers in the skin, muscle, and joints.
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Perineurial repair involves the individual fascicles and placing sutures through the perineurium, the protective sheath surrounding fascicles, the nerve fibers enclosed by the perineurium. Trauma to the nerve by cutting out each fascicle and fibrosis, a build up of tissue as a reaction, that develops due to the dissections and number of sutures is a problem.Wolford, Larry M., and Eber Stevao. "Considerations in Nerve Repair." BUMC Proceedings 16 (2003): 152-56.
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Injuries to the brachial plexus result from excessive stretching or tearing of the C5-T1 nerve fibers. These injuries can be located in front of or behind the clavicle, nerve disruptions, or root avulsions from the spinal cord. These injuries are diagnosed based on clinical exams, axon reflex testing, and electrophysiological testing. Brachial plexus injuries require quick treatment in order for the patient to make a full functional recovery (Tung, 2003).
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Throughout human evolution, the first thoracic and inferior cervical ganglia merged - and this resulting ganglion is called the stellate ganglion (so called because of its radiating pattern similar in appearance to a star). The general rule of interaction of the nerve fibers in the sympathetic nervous system begins at the spinal cord. Here they arise from the thoracolumbar (T1-L2) regions' lateral horn of grey and emerge via the ventral root.
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From there on, umbellulone is able to reach the perivascular sensory nerve endings of the meningeal vessels. Stimulation of these nerve fibers will eventually lead to the release of CGRP, a nociceptor known for its ability to induce migraine and cluster headache attacks. Activation of TRPA1 by umbellulone results in the opening of this ion channel. Calcium will enter the cell and the cell membrane will be depolarised.
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The vesical nervous plexus arises from the forepart of the pelvic plexus. The nerves composing it are numerous, and contain a large proportion of spinal nerve fibers. They accompany the vesicle arteries, and are distributed to the sides and fundus of the bladder. Numerous filaments also pass to the seminal vesicles and vas deferens; those accompanying the vas deferens join, on the spermatic cord, with branches from the spermatic plexus.
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As early as 1845, while still at Zurich, he supplied the clear proof that nerve fibers are continuous with nerve cells, and so furnished the absolutely necessary basis for all sound speculations as to the actions of the central nervous system. From that time onward he continually laboured at the histology of the nervous system, and more especially at the difficult problems presented by the intricate patterns in which nerve fibers and neurons are woven together in the brain and spinal cord. From his early days a master of method, he saw at a glance the value of the new Golgi staining method for the investigation of the central nervous system, and, to the great benefit of science, took up once more in his old age, with the aid of a new means, the studies for which he had done so much in his youth. Kölliker contributed greatly to knowledge of the inner structure of the brain.
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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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Created May 8, 1999, revised 16 January 2007. The nerve supply generally enters from the bone apical to the tooth and forms a network around the tooth toward the crest of the gingiva. When pressure is exerted on a tooth, such as during chewing or biting, the tooth moves slightly in its socket and puts tension on the periodontal ligaments. The nerve fibers can then send the information to the central nervous system for interpretation.
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It is caused by an underlying collection of gray matter known as the spinal trigeminal nucleus. The gray matter of this nucleus is covered by a layer of nerve fibers that form the spinal tract of the trigeminal nerve. The base of the medulla is defined by the commissural fibers, crossing over from the ipsilateral side in the spinal cord to the contralateral side in the brain stem; below this is the spinal cord.
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Longer nerve fibers are affected to a greater degree than shorter ones because nerve conduction velocity is slowed in proportion to a nerve's length. In this syndrome, decreased sensation and loss of reflexes occurs first in the toes on each foot, then extends upward. It is usually described as a glove-stocking distribution of numbness, sensory loss, dysesthesia and night time pain. The pain can feel like burning, pricking sensation, achy or dull.
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Otto earned his B. A. degree in Zoology and Physics from Washington University in June 1934. Upon graduation from his undergraduate program, he smoothly transitioned into his graduate work at the same institution. Once again, his older brother had a pronounced influence on his research and education. Francis, a physiologist, was studying “the molecular organization of cells and tissues with particular reference to nerve fibers.” [Schmitt] Otto adopted this topic for his graduate research.
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In addition, individuals with Zellweger syndrome can show a reduction in central nervous system (CNS) myelin (particularly cerebral), which is referred to as hypomyelination. Myelin is critical for normal CNS functions, and in this regard, serves to insulate nerve fibers in the brain. Patients can also show postdevelopmental sensorineuronal degeneration that leads to a progressive loss of hearing and vision. Zellweger syndrome can also affect the function of many other organ systems.
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Paris as seen with full visual fields In binasal hemianopsia, vision is missing in the inner (nasal or medial) half of both the right and left visual fields. Information from the nasal visual field falls on the temporal (lateral) retina. Those lateral retinal nerve fibers do not cross in the optic chiasm. Calcification of the internal carotid arteries can impinge the uncrossed, lateral retinal fibers, leading to loss of vision in the nasal field.
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Percutaneous electrical nerve stimulation, or PENS, is used mainly in the treatment of intractable pain associated with chronic low back pain syndrome, cancer, and other disorders. It is a technique involving insertion of an ultra-fine acupuncture needle which probes into the soft tissues or muscles to electrically stimulate nerve fibers in the sclerotomal, myotomal, or dermatomal distribution corresponding to the patient's pain symptoms. PENS is related to both electroacupuncture and transcutaneous electrical nerve stimulation.
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Nociception: The reflex arc of a dog with a pin in her paw. Note there is no communication to the brain, but the paw is withdrawn by nervous impulses generated by the spinal cord. There is no conscious interpretation of the stimulus by the dog. Nociception usually involves the transmission of a signal along a chain of nerve fibers from the site of a noxious stimulus at the periphery to the spinal cord and brain.
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In some cases of brachial plexopathy, no treatment is required and recovery happens on its own. Treatment for lumbosacral plexopathy that is not caused by trauma, but instead from diabetic plexopathy, is directed at controlling the person's blood sugar level. By preventing the deterioration of the nerve fibers from hyperglycemia, patients may recover significant muscle strength. For radiation-induced plexopathies, treatment options are limited to pain/symptom management and provision of assistive devices.
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The fingers themselves were fused and immobile, and may have lacked claws. Carnotaurus differed from all other abelisaurids in having proportionally shorter and more robust forelimbs, and in having the fourth, splint-like metacarpal as the longest bone in the hand. A 2009 study suggests that the arms were vestigial in abelisaurids, because nerve fibers responsible for stimulus transmission were reduced to an extent seen in today's emus and kiwis, which also have vestigial forelimbs.
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Hair plexus. A hair plexus or root hair plexus is a special group of nerve fiber endings and serves as a very sensitive mechanoreceptor for touch sensation. Each hair plexus forms a network around a hair follicle and is a receptor, which means it sends and receives nerve impulses to and from the brain when the hair moves. Endings of sensory nerve fibers which form a plexus around a hair follicle in hairy skin.
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Remak bundles in the distal peripheral nerve are clustered with other Remak bundles. The Remak Schwann cells have been shown to be electrochemically responsive to action potentials of the axons contained within them. In experiments where nerve injury is caused but nearby C fibers remain intact, increased spontaneous activity in the C fibers is observed. This phenomenon supports the theory that damaged nerve fibers may release factors that alter the function of neighboring undamaged fibers.
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When coming in contact with your tongue (or any internal surface), the capsaicin de-polarizes the nerve fibers, allowing sodium and calcium into the fibers. In order for fibers to do so, they must have a specific thermoreceptor. The thermoreceptor reacting to capsaicin and other heat producing chemicals is known as TRPV1. In response to heat, the TRPV1 receptor opens up passages that allow ions to pass through, causing the sensation of heat or burning.
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An MRI derivative technique known as diffusion tensor imaging (DTI) is used to determine the orientation and integrity of specific nerve pathways, allowing the detection of damage. When imaging those with alcoholism, the DTI results show that heavy drinking disrupts the microstructure of nerve fibers. Another MRI derivative technique, magnetic resonance spectroscopy imaging (MRSI), can provide further information about the brain's neurochemistry and can detect the distribution of certain metabolites, neurotransmitters, and alcohol.
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Metachromatic leukodystrophy (MLD) is a lysosomal storage disease which is commonly listed in the family of leukodystrophies as well as among the sphingolipidoses as it affects the metabolism of sphingolipids. Leukodystrophies affect the growth and/or development of myelin, the fatty covering which acts as an insulator around nerve fibers throughout the central and peripheral nervous systems. MLD involves cerebroside sulfate accumulation. Metachromatic leukodystrophy, like most enzyme deficiencies, has an autosomal recessive inheritance pattern.
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Ganglioneuroma is a rare and benign tumor of the autonomic nerve fibers arising from neural crest sympathogonia, which are completely undifferentiated cells of the sympathetic nervous system. However, ganglioneuromas themselves are fully differentiated neuronal tumors that do not contain immature elements. Ganglioneuromas most frequently occur in the abdomen, however these tumors can grow anywhere sympathetic nervous tissue is found. Other common locations include the adrenal gland, paraspinal retroperitoneum, posterior mediastinum, head, and neck.
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The single sucrose gap technique is used to study the electrical activity of cells. It is useful in the study of small nerve fibers and electrically connected cells such as smooth muscle cell. The method creates conduction block in a nerve or muscle fiber by introducing a gap of high resistance between two groups of cells. A nonionic sucrose solution is used to increase resistance in the extracellular area between the two groups.
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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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In 1902 he founded the journal Zeitschrift für Allgemeine Physiologie (Journal of General Physiology), and was its publisher until his death in 1921. Max Verworn is remembered for his research in the field of experimental physiology, and especially for his work involving cellular physiology. He did extensive studies of the elementary physiological processes that take place in muscle tissue, nerve fibers and sensory organs. He conducted research in the fields of phylogenesis and ontogenesis.
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Nociception: The reflex arc of a dog with a pin in her paw. Note there is no communication to the brain, but the paw is withdrawn by nervous impulses generated by the spinal cord. There is no conscious interpretation of the stimulus by the dog. Nociception usually involves the transmission of a signal along a chain of nerve fibers from the site of a noxious stimulus at the periphery to the spinal cord and brain.
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Leukodystrophies are a group of usually inherited disorders characterized by degeneration of the white matter in the brain. The word leukodystrophy comes from the Greek roots leuko, "white", dys, "abnormal" and troph, "growth". The leukodystrophies are caused by imperfect growth or development of the myelin sheath, the fatty insulating covering around nerve fibers. Leukodystrophies may be classified as hypomyelinating or demyelinating diseases, depending on whether the damage is present before birth or occurs after.
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Autonomic Nervous System Autonomic neuropathy (AN or AAN) is a form of polyneuropathy that affects the non-voluntary, non-sensory nervous system (i.e., the autonomic nervous system), affecting mostly the internal organs such as the bladder muscles, the cardiovascular system, the digestive tract, and the genital organs. These nerves are not under a person's conscious control and function automatically. Autonomic nerve fibers form large collections in the thorax, abdomen, and pelvis outside the spinal cord.
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Erlanger, a graduate of Johns Hopkins University, first achieved notice as a cardiologist, but achieved his greatest success in the field of neurophysiology. In collaboration with Herbert Spencer Gasser, he developed apparatus for making detailed sensitive measurements of electrical charges that passed through nerve fibers, establishing a relationship between the level of action potential and the nerve diameter. For this, he and Gasser shared the 1944 Nobel Prize in Physiology or Medicine.
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The radial nerve, like any other in the nervous system, is vulnerable to damage. This damage can originate when the nerve fibers experience pressure, stretching, or cutting. All of the tissues can prevent action potentials from continuing up or down axons within the nerve, which would interrupt signal transduction to and from the brain. As a result of the interrupted signal, the patient may experience loss of feeling and/or motor control.
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Examples of sinusoidally amplitude- and frequency-modulated signals The neural representation of stimulus envelope, ENVn, has typically been studied using well-controlled ENVp modulations, that is sinusoidally amplitude-modulated (AM) sounds. Cochlear filtering limits the range of AM rates encoded in individual auditory-nerve fibers. In the auditory nerve, the strength of the neural representation of AM decreases with increasing modulation rate. At the level of the cochlear nucleus, several cell types show an enhancement of ENVn information.
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Association fibers are axons that connect cortical areas within the same cerebral hemisphere. In human neuroanatomy, axons (nerve fibers) within the brain, can be categorized on the basis of their course and connections as association fibers, projection fibers, and commissural fibers. The association fibers unite different parts of the same cerebral hemisphere, and are of two kinds: (1) short association fibers that connect adjacent gyri; (2) long association fibers that make connections between more distant parts.
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How this might lead to instantaneous unconsciousness is not explained. In this earliest of Star Trek reference books, the pinch is referred to as the "Spock Pinch." In the Star Trek: Voyager episode "Cathexis", the Doctor inspects a crewmember who was found unconscious and observes an extreme trauma to the trapezius neck bundle, "as though her nerve fibers have been ruptured"; and it is later revealed that the person was the victim of a nerve pinch.
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Strychnine is a neurotoxin which acts as an antagonist of glycine and acetylcholine receptors. It primarily affects the motor nerve fibers in the spinal cord which control muscle contraction. An impulse is triggered at one end of a nerve cell by the binding of neurotransmitters to the receptors. In the presence of an inhibitory neurotransmitter, such as glycine, a greater quantity of excitatory neurotransmitters must bind to receptors before there will be an action potential generated.
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Nerve fibers with noradrenaline in the iris The catecholamines comprise the endogenous substances dopamine, noradrenaline (norepinephrine) and adrenaline (epinephrine) as well as numerous artificially synthesized compounds such as isoprenaline. Their investigation constitutes a prominent chapter in the history of physiology, biochemistry and pharmacology. Adrenaline was the first hormone extracted from its endocrine gland and obtained in pure form, before the word hormone was coined. It was also the first hormone the structure and biosynthesis of which were clarified.
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Therefore, the starting innervation of the developing teeth is involved with the sensory innovation of the future periodontal ligament and pulp. Nerve fibers never enters the enamel organ. Nerve-related signaling molecules, such as Glial cell line-derived growth factor, Neurotrophin and semaphoring are among the few which have been studied during the tooth development process. Of which, the verve-related signaling molecules seems to show a trend that suggest an early implication of innervation of tooth development.
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Based on the tooth injury, sensory nerve fibers react to pulpitis by growing terminal branches into the adjacent surviving pulp, which also changes the cytochemical phenotype. This neural growth typically lasts few a few days and function and form is retained. Thus, pain is poorly localized, and the level of pain stemming from pulpitis varies based on severity, quality, duration, onset, trigger. As caries invades dentin, the number of permeable dentinal tubules correlates with the degree of pain.
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There are several different surgical approaches that can be used to complete this procedure: the middle cranial fossa, retrolabrynthine, retrosigmoid, and translabrynthine. The middle cranial fossa approach is one that most often requires neurosurgical expertise. The advantage of this procedure is that the vestibular nerve is clearly visible and can be sectioned without harming the cochlear nerve fibers. The general procedure begins by positioning the patient supine with the head turned to the side with surgical ear upright.
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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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Cephalopods have large, well-developed brains, and their brain-to-body mass ratio is the largest among the invertebrates, falling between that of endothermic and ectothermic vertebrates. The nervous system of cephalopods is the most complex of all invertebrates. The giant nerve fibers of the cephalopod mantle have been widely used for many years as experimental material in neurophysiology; their large diameter (due to lack of myelination) makes them relatively easy to study compared with other animals.
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Myelinated GS efferent fiber leaving cell body of motor neuron to form a neuromuscular junction The efferent nerve fibers of motor neurons are involved in muscle control, both skeletal and smooth muscle. The cell body of the motor neuron is connected to a single, long axon and several shorter dendrites projecting out of the cell body itself. This axon then forms a neuromuscular junction with the effectors. The cell body of the motor neuron is satellite-shaped.
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Another 20th-century theory was gate control theory, introduced by Ronald Melzack and Patrick Wall in the 1965 Science article "Pain Mechanisms: A New Theory". The authors proposed that both thin (pain) and large diameter (touch, pressure, vibration) nerve fibers carry information from the site of injury to two destinations in the dorsal horn of the spinal cord, and that the more large fiber activity relative to thin fiber activity at the inhibitory cell, the less pain is felt.
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Without this enzyme, sulfatides build up in many tissues of the body, eventually destroying the myelin sheath of the nervous system. The myelin sheath is a fatty covering that protects nerve fibers. Without it, the nerves in the brain (central nervous system – CNS) and the peripheral nerves (peripheral nervous system – PNS) which control, among other things the muscles related to mobility, cease to function properly. Arylsulfatase A is activated by saposin B (Sap B), a non-enzymatic proteinaceous cofactor.
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Canavan disease is caused by a defective ASPA gene which is responsible for the production of the enzyme aspartoacylase. Decreased aspartoacylase activity prevents the normal breakdown of N-acetyl aspartate, wherein the accumulation of N-acetylaspartate, or lack of its further metabolism interferes with growth of the myelin sheath of the nerve fibers of the brain. The myelin sheath is the fatty covering that surrounds nerve cells and acts as an insulator, allowing for efficient transmission of nerve impulses.
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The disease is one in a group of genetic disorders collectively known as leukodystrophies that affect growth of the myelin sheath, the fatty covering—which acts as an insulator—on nerve fibers in the central nervous system. The several forms of Pelizaeus–Merzbacher disease include classic, connatal, transitional, and adult variants. Milder mutations of the PLP1 gene that mainly cause leg weakness and spasticity, with little or no cerebral involvement, are classified as spastic paraplegia 2 (SPG2).
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Layout of the brain A startle reflex can occur in the body through a combination of actions. A reflex from hearing a sudden loud noise will happen in the primary acoustic startle reflex pathway consisting of three main central synapses, or signals that travel through the brain. First, there is a synapse from the auditory nerve fibers in the ear to the cochlear root neurons (CRN). These are the first acoustic neurons of the central nervous system.
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Several large organizations within the dairy industry are against tail docking because of the lack of scientific evidence supporting claims benefiting the practice. Scientific studies have demonstrated that there are numerous animal welfare issues with this practice (such as distress, pain, increased activity in pain receptors in the tail stump, abnormal growths of nerve fibers, sensitivity to heat and cold, and clostridial diseases). Fortunately, there is an effective and humane alternative to tail docking, which is switch trimming.
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A fractured cribriform plate can result in olfactory dysfunction, septal hematoma, cerebrospinal fluid rhinorrhoea (CSF rhinorrhoea), and possibly infection which can lead to meningitis. CSF rhinorrhoea (clear fluid leaking from the nose) is very serious and considered a medical emergency. Aging can cause the openings in the cribriform plate to close, pinching olfactory nerve fibers. A reduction in olfactory receptors, loss of blood flow, and thick nasal mucus can also cause an impaired sense of smell.
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Preclinical data support the notion that Substance P is an important element in pain perception. The sensory function of substance P is thought to be related to the transmission of pain information into the central nervous system. Substance P coexists with the excitatory neurotransmitter glutamate in primary afferents that respond to painful stimulation. Substance P and other sensory neuropeptides can be released from the peripheral terminals of sensory nerve fibers in the skin, muscle, and joints.
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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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Phase-locking is known as matching amplitude times to a certain phase of another waveform. In the case of auditory neurons, this means firing an action potential at a certain phase of a stimulus sound being delivered. It has been seen that when being played a pure tone, auditory nerve fibers will fire at the same frequency as the tone. Volley theory suggests that groups of auditory neurons use phase-locking to represent subharmonic frequencies of one harmonic sound.
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A double sucrose-gap is generally advantageous when used to electrically isolate smaller segments of nerve fibers than would be possible with a single sucrose-gap, as was done in studies on membrane potentials and currents in sheep and calf ventricular muscle fibers. The double sucrose-gap technique is also utilized over the single sucrose-gap to study cardiac muscle, where it allows for clearer resolution of early currents, those occurring within the first 10-100 milliseconds of depolarization.
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Its performance in ruling out endometriosis is low. CA-125 levels appear to fall during endometriosis treatment, but has not shown a correlation with disease response. Another review in 2011 identified several putative biomarkers upon biopsy, including findings of small sensory nerve fibers or defectively expressed β3 integrin subunit. It has been postulated a future diagnostic tool for endometriosis will consist of a panel of several specific and sensitive biomarkers, including both substance concentrations and genetic predisposition.
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In neuropathy associated with diabetes mellitus characterized by alteration in small nerve fibers, a reduction in time domain parameters of HRV seems not only to carry negative prognostic value but also to precede the clinical expression of autonomic neuropathy. In diabetic patients without evidence of autonomic neuropathy, reduction of the absolute power of LF and HF during controlled conditions was also reported. Similarly, diabetic patients can be differentiated from normal controls on the basis of reduction in HRV.
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Reflex arc of a dog when its paw is stuck with a pin. The spinal cord responds to signals from receptors in the paw, producing a reflex withdrawal of the paw. This localized response does not involve brain processes that might mediate a consciousness of pain, though these might also occur. Nociception usually involves the transmission of a signal along nerve fibers from the site of a noxious stimulus at the periphery to the spinal cord.
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Vasoconstriction and vasodilation, an effect that can be caused from axon reflex stimulation in certain tissues, demonstrated compared to the normal blood vessel. In dermal circulation, the axon reflex controls the temperature and circulation in the tissues through vasodilation. Small nerve fibers called thermoreceptors are sensitive to temperature and can act as sensors that initiate axon reflex mediated vasodilation. Neuromuscular diseases can be predicted early by the presence of abnormal muscle fiber reflexes and corresponding twitches.
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White matter tracts within a human brain, as visualized by MRI tractography A nerve tract is a bundle of nerve fibers (axons) connecting nuclei of the central nervous system. In the peripheral nervous system this is known as a nerve, and has associated connective tissue. The main nerve tracts in the central nervous system are of three types: association fibers, commissural fibers, and projection fibers. A tract may also be referred to as a commissure, fasciculus or decussation.
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The interthalamic adhesion contains nerve cells and nerve fibers; a few of the latter may cross the middle line, but most of them pass toward the middle line and then curve laterally on the same side. It is still uncertain whether the interthalamic adhesion contains fibers that cross the mid-line and for this reason it is inappropriate to call it a commissure. The interthalamic adhesion is notably enlarged in patients with the type II Arnold–Chiari malformation.
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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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The vertebrate cerebrum (brain) is formed by two cerebral hemispheres that are separated by a groove, the longitudinal fissure. The brain can thus be described as being divided into left and right cerebral hemispheres. Each of these hemispheres has an outer layer of grey matter, the cerebral cortex, that is supported by an inner layer of white matter. In eutherian (placental) mammals, the hemispheres are linked by the corpus callosum, a very large bundle of nerve fibers.
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The principal nucleus represents touch-position sensation from the face. It is located in the pons, near the entrance for the fifth nerve. Fibers carrying touch-position information from the face and mouth via cranial nerves V, VII, IX, and X are sent to this nucleus when they enter the brainstem. The principal nucleus contains a touch-position sensory map of the face and mouth, just as the spinal trigeminal nucleus contains a complete pain-temperature map.
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Ephaptic transmission is when two nerves communicate with each other via an artificial synapse between nerves. Healthy peripheral nerves are insulated with a myelin sheath that helps to both enhance electric transmission and to prevent cross-talk between parallel nerves. After a lesion, it has been observed that regenerating nerves might not be myelinated effectively. Consequently, the two nerve fibers can come into contact and provide a means for an impulse to be directly conducted through the nerve membrane.
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The perception model of ENV processing that incorporates selective (bandpass) AM filters accounts for many perceptual consequences of cochlear dysfunction including enhanced sensitivity to AM for sinusoidal and noise carriers, abnormal forward masking (the rate of recovery from forward masking being generally slower than normal for impaired listeners), stronger interference effects between AM and FM and enhanced temporal integration of AM. The model of Torsten Dau has been extended to account for the discrimination of complex AM patterns by hearing-impaired individuals and the effects of noise-reduction systems. The performance of the hearing-impaired individuals was best captured when the model combined the loss of peripheral amplitude compression resulting from the loss of the active mechanism in the cochlea with an increase in internal noise in the ENVn domain. Phenomenological models simulating the response of the peripheral auditory system showed that impaired AM sensitivity in individuals experiencing chronic tinnitus with clinically normal audiograms could be predicted by substantial loss of auditory-nerve fibers with low spontaneous rates and some loss of auditory-nerve fibers with high-spontaneous rates.
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Each cell is attached to a tiny triangular frame. The 'hairs' are minute processes on the end of the cell, which are very sensitive to movement. When the vibration of the membrane rocks the triangular frames, the hairs on the cells are repeatedly displaced, and that produces streams of corresponding pulses in the nerve fibers, which are transmitted to the auditory pathway. The outer hair cells feed back energy to amplify the traveling wave, by up to 65 dB at some locations.
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Although only limited effects of age and hearing loss have been observed in terms of TFSn coding strength of narrowband sounds, more dramatic deficits have been observed in TFSn coding quality in response to broadband sounds, which are more relevant for everyday listening. A dramatic loss of tonotopicity can occur following noise induced hearing loss, where auditory-nerve fibers that should be responding to mid frequencies (e.g., 2–4 kHz) have dominant TFS responses to lower frequencies (e.g., 700 Hz).
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Corpus callosotomy is a palliative procedure for specially severe cases of epilepsy. This corpus callosum is a large bundle of nerve fibers that connects both brain halves with each other. To prevent the spreading of seizures from one brain hemisphere (brain half) to the other the corpus callosum can be split. This procedure is mostly carried out on patients with so-called drop attacks that come with a very high risk of injury and in which the epileptic focus is not clearly delimitable.
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Multiple subpial transection (MST) is a palliative procedure that is considered when an epileptic focus can be identified but cannot be removed because it is in a functionally relevant brain region- a so- called eloquent region. In an MST nerve fibers are disconnected so that seizures cannot spread from the epileptic focus into the rest of the brain. Between 60 and 70% of patients experienced a seizure reduction of over 95% after an MST and the risk for neurologic deficits is around 19%.
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The parasympathetic nervous system has many neighboring fibers that respond to different stimuli. When one stimulus activates multiple nerve fibers of the parasympathetic nervous system, parasympathetic generalization is occurring. There is a possibility that sensory input from the eyes could travel to the neurons in the cortex that interpret such signals, but neighboring neurons which are involved in sneezing are also activated, due to the generalization. This could lead to a sneeze in response to a stimulus other than nasal irritation.
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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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Motor information travels from the brain down the spinal cord via descending spinal cord tracts. Descending tracts involve two neurons: the upper motor neuron (UMN) and lower motor neuron (LMN).Saladin. Anatomy and Physiology, 5th Ed. A nerve signal travels down the upper motor neuron until it synapses with the lower motor neuron in the spinal cord. Then, the lower motor neuron conducts the nerve signal to the spinal root where efferent nerve fibers carry the motor signal toward the target muscle.
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Seddon classified facial nerve injuries into three broad categories: neuropraxia, neurotmesis, and axonotmesis. Neuropraxia is the most common form of injury associated with Bell's palsy, and it is characterized by paralysis without a degeneration of the peripheral nerve. Electroneuronography would yield a normal or mildly impaired response, as the nerve fibers are still whole but unresponsive to conscious control. Neurotmesis is regarded as the worst possible outcome, with electroneuronography readings equivalent to a flat line, or no response to stimulation.
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The left and right hemispheres operate the contralateral sides of the body. Each hemisphere contains sections of all 4 lobes: the frontal lobe, parietal lobe, temporal lobe, and occipital lobe. The two hemispheres are separated along the mediated longitudinal fissure and are connected by the corpus callosum which allows for communication and coordination of stimuli and information. The corpus callosum is the largest collective pathway of white matter tissue in the body that is made of more than 200 million nerve fibers.
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In severe cases, there was congestion of hemal sinuses, two principal empty areas along the digestive tube and vessels. Mass amounts of yeast-like cells compressed nerve fibers and the gill lamellae were destroyed. Mollusks clinical signs vary from scattered spots of brownish discoloration on the mantle tissues to general deterioration of mussel condition. In severe cases, there were black-bodied mussels with a distinct odor and black yeast-cells infected the connective tissues around the gonads and the digestive tract.
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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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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 pyramidal tracts include both the corticobulbar tract and the corticospinal tract. These are aggregations of efferent nerve fibers from the upper motor neurons that travel from the cerebral cortex and terminate either in the brainstem (corticobulbar) or spinal cord (corticospinal) and are involved in the control of motor functions of the body. The corticobulbar tract conducts impulses from the brain to the cranial nerves.Chapter 9 of "Principles of Physiology" (3rd edition) by Robert M. Berne and Mathew N. Levy.
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The nerve axons traveling down the tract are the efferent nerve fibers of the upper motor neurons. These axons travel down the tracts in the white matter of the spinal cord until they reach the vertebral level of the muscle that they will innervate. At this point, the axons synapse with lower motor neurons. The majority of axons do not directly synapse with lower motor neurons, but instead synapse with an interneuron that then synapses with a lower motor neuron.
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He initially believed the cysts were the result of meningeal diverticula and long arachnoid prolongations. It wasn't until 10 years later that he discovered their significance, and that these cysts can appear symptomatic in patients. An important distinguishing factor is that the walls of Tarlov cysts contain nerve fibers, in contrast to the meningeal diverticula which has no evidence of neural elements. In 1951, Tarlov joined New York Medical College as a professor of neurology and neurosurgery, and director of the neurology department.
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Archiacanthocephala is a class within the phylum of Acanthocephala.Crompton, David William Thomasson; Nickol, Brent B.: Biology of the Acanthocephala, Cambridge University Press, 1985, p. 31\. They are microscopic parasitic worms that attach themselves to the intestinal wall of terrestrial vertebrates, including humans. They are characterised by the body wall and the lemnisci (which are a bundle of sensory nerve fibers), which have nuclei that divide without spindle formation or the appearance of chromosomes or it has a few amoebae-like giant nuclei.
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In the 11th century, Avicenna theorized that there were a number of feeling senses including touch, pain and titillation. Portrait of René Descartes by Jan Baptist Weenix, 1647-1649 In 1644, René Descartes theorized that pain was a disturbance that passed down along nerve fibers until the disturbance reached the brain. Descartes's work, along with Avicenna's, prefigured the 19th-century development of specificity theory. Specificity theory saw pain as "a specific sensation, with its own sensory apparatus independent of touch and other senses".
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There is reduced axonal transport (and hence backlog and accumulation of intracellular products) within the nerves because of the ischemia. This then causes the nerve fibers to be damaged by swelling in the surface layer of the retina. A 1981 analysis concluded that "in most instances, cotton-wool spots do not represent the whole area of ischaemic inner retina but merely reflect the obstruction of axoplasmic flow in axons crossing into much larger ischaemic areas". Associated findings include microvascular infarcts and hemorrhages.
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In 2012, neuroscientists at UCLA conducted an experiment using a virtual taxi video game connected to seven epilepsy patients with electrodes already implanted in their brains, allowing the researchers to monitor neuronal activity whenever memories were being formed. As the researchers stimulated the nerve fibers of each of the patients' entorhinal cortex as they were learning, they were then able to better navigate themselves through various routes and recognize landmarks more quickly. This signified an improvement in the patients' spatial memory.
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Sympathetic nerve fibers travel around the tunica media of the artery, secrete neurotransmitters such as norepinephrine into the extracellular fluid surrounding the smooth muscle (tunica media) from the terminal knob of the axon. The smooth muscle cell membranes have α and β-adrenergic receptors for these neurotransmitters. Activation of α-adrenergic receptors promotes vasoconstriction, while the activation of β-adrenergic receptors mediates the relaxation of muscle cells, resulting in vasodilation. Normally, α-adrenergic receptors predominates in smooth muscle of resistance vessels.
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It has been found that the snake's visual and infrared maps of the world are overlaid in the optic tectum. This combined information is relayed via the tectum to the forebrain. The nerve fibers in the pit organ are constantly firing at a very low rate. Objects that are within a neutral temperature range do not change the rate of firing; the neutral range is determined by the average thermal radiation of all objects in the receptive field of the organ.
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Laura Forster declares that Santiago Ramón y Cajal suggested she focused her research in the lab on whether the degeneration of nerve fibers after traumatic lesion of the spinal cord in birds corresponded with events observed in previous studies on mammals performed by Cajal himself and others. Forster’s study was the first time that neurofibrillary techniques were applied to birds for this purpose and her results demonstrated similarities with the process in mammals, although these occurred more rapidly in birds.
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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 esophagus is innervated by the vagus nerve and the cervical and thoracic sympathetic trunk. The vagus nerve has a parasympathetic function, supplying the muscles of the esophagus and stimulating glandular contraction. Two sets of nerve fibers travel in the vagus nerve to supply the muscles. The upper striated muscle, and upper esophageal sphincter, are supplied by neurons with bodies in the nucleus ambiguus, whereas fibers that supply the smooth muscle and lower esophageal sphincter have bodies situated in the dorsal motor nucleus.
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The somatic motor fibers that innervate the laryngeal and pharyngeal muscles are located in the nucleus ambiguus and emerge from the medulla in the cranial root of the accessory nerve. Fibers cross over to and join the vagus nerve in the jugular foramen. Sensory cell bodies are located in the inferior jugular ganglion, and the fibers terminate in the solitary nucleus. Parasympathetic fibers to segments of the trachea and esophagus in the neck originate in the dorsal nucleus of the vagus nerve.
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On March 24, 1899, Brödel was diagnosed with a streptococcus infection on his hand and arm, caused by improper practice of handling anatomical dissections without gloves. He required several operations on his left arm, including one to separate nerve fibers from the scar tissue. These operations were performed by Dr. William S. Halsted, Chief of Surgery at Johns Hopkins Hospital. Capitalizing on this experience, Brödel illustrated and detailed his medical condition and the resulting numbness of his nondominant left hand.
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The wall of the neural tube consists of neuroepithelial cells, which differentiate into neuroblasts, forming the mantle layer (the gray matter). Nerve fibers emerge from these neuroblasts to form the marginal layer (the white matter). The ventral part of the mantle layer (the basal plates) forms the motor areas of the spinal cord, whilst the dorsal part (the alar plates) forms the sensory areas. Between the basal and alar plates is an intermediate layer that contains neurons of the autonomic nervous system.
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Sensory pathways from the periphery to the cortex are separate for touch-position and pain-temperature sensations. All sensory information is sent to specific nuclei in the thalamus. Thalamic nuclei, in turn, send information to specific areas in the cerebral cortex. Each pathway consists of three bundles of nerve fibers connected in series: alt=Flow chart from sensory receptors to the cerebral cortex The secondary neurons in each pathway decussate (cross the spinal cord or brainstem), because the spinal cord develops in segments.
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The infant brain will increase in size by a factor of up to 5 by adulthood, reaching a final size of approximately 86 (± 8) billion neurons. Two factors contribute to this growth: the growth of synaptic connections between neurons and the myelination of nerve fibers; the total number of neurons, however, remains the same. After adolescence, the volume of the synaptic connections decreases again due to synaptic pruning. Pruning is influenced by environmental factors and is widely thought to represent learning.
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He believed that a child’s growth & development are influenced by both their environment and genes, but he largely investigated the children's physiological development. He called this process maturation, that is, the process by which development is governed by intrinsic factors, principally the genes. According to Gesell, the rate at which children develop primarily depends on the growth of their nervous system, consisting of the complicated web of nerve fibers, spinal cord, and brain. As the nervous system grows, their minds develop and their behaviors change accordingly.
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As part of the human immune response, white blood cell-derived macrophages may engulf M. leprae by phagocytosis. In the initial stages, small sensory and autonomic nerve fibers in a person with Leprosy's skin are damaged. This damage usually results in hair loss to the area, a loss of the ability to sweat, and numbness (decreased ability to detect sensations such as temperature and touch). Further peripheral nerve damage may result in skin dryness, more numbness, and muscle weaknesses or paralysis in the area affected.
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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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This information is then received by the cochlear implant's internal components. The receiver stimulator delivers the correct amount of electrical stimulation to the appropriate electrodes on the array to represent the sound signal that was detected. The electrode array stimulates the remaining auditory nerve fibers in the cochlea, which carry the signal on to the brain, where it is processed. One way to measure the developmental status and limits of plasticity of the auditory cortical pathways is to study the latency of cortical auditory evoked potentials (CAEP).
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As for autopsies, the principal work of the neuropathologist is to help in the post-mortem diagnosis of various forms of dementia and other conditions that affect the central nervous system. Tissue samples are researched within the lab for diagnosis as well as forensic investigations. Biopsies can also consist of the skin. Epidermal nerve fiber density testing (ENFD) is a more recently developed neuropathology test in which a punch skin biopsy is taken to identify small fiber neuropathies by analyzing the nerve fibers of the skin.
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Schwann was particularly interested in nervous and muscular tissues. As part of his efforts to classify bodily tissues in terms of their cellular nature, he discovered the cells that envelope the nerve fibers, which are now called Schwann cells in his honor. How the fatty myelin sheaths of peripheral nerves were formed was a matter of debate that could not be answered until the electron microscope was invented. All axons in the peripheral nervous system are now known to be wrapped in Schwann cells.
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Satellite glial cells (or satellite cells) (formerly called amphicytes) are glial cells that cover the surface of neuron cell bodies in ganglia of the peripheral nervous system. Thus, they are found in sensory, sympathetic, and parasympathetic ganglia. Both satellite glial cells (SGCs) and Schwann cells (the cells that ensheathe some nerve fibers in the PNS) are derived from the neural crest of the embryo during development. SGCs have been found to play a variety of roles, including control over the microenvironment of sympathetic ganglia.
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In neuroanatomy, a nucleus (plural form: nuclei) is a cluster of neurons in the central nervous system, located deep within the cerebral hemispheres and brainstem. The neurons in one nucleus usually have roughly similar connections and functions. Nuclei are connected to other nuclei by tracts, the bundles (fascicles) of axons (nerve fibers) extending from the cell bodies. A nucleus is one of the two most common forms of nerve cell organization, the other being layered structures such as the cerebral cortex or cerebellar cortex.
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In order to detect low frequency fields and DC fields, fish have specialized receptors to read and process the incoming information. The ampullary electrosensory systems of fish and amphibians are modified hair cell sensors with similarities to the lateral line system and audition. Ampullary receptors pores on the skins of the animal, and each pore opens to a water or jelly filled tube which leads to the terminal swelling. Outer faces contact the ampullary lumen via the aquatic environment while the inner faces synapse with nerve fibers.
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Frontal sinus. Frontal sinuses are rarely symmetrical and the septum between them frequently deviates to one or other side of the middle line. Their average measurements are as follows: height 28 mm, breadth 24 mm, depth 20 mm, creating a space of 6-7 ml.University of Texas Medical Branch The mucous membrane in this sinus is innervated by the supraorbital nerve, which carries the postganglionic parasympathetic nerve fibers for mucous secretion from the ophthalmic nerve and supplied by the supraorbital artery and anterior ethmoidal artery.
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Springer–Verlag, Tokyo, pp 81–90 They attach themselves to the intestinal wall using a hook covered proboscis. The location of the eight cement glands in the male is one of the few ways to distinguish the dorsal and ventral sides of these organisms. The worms are also characterised by the body wall and the lemnisci (which are a bundle of sensory nerve fibers), which have nuclei that divide without spindle formation or the appearance of chromosomes or it has a few amoebae-like giant nuclei.
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The hypotheses of the neuron doctrine were supported by experiments following Galvani's pioneering work in the electrical excitability of muscles and neurons. In 1898, British scientist John Newport Langley first coined the term "autonomic" in classifying the connections of nerve fibers to peripheral nerve cells. Langley is known as one of the fathers of the chemical receptor theory, and as the origin of the concept of "receptive substance". Towards the end of the nineteenth century Francis Gotch conducted several experiments on nervous system function.
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The most common cause of the latter is orthostatic hypotension (also called postural hypotension). Fever, hyperventilation, diarrhea and severe infections can also cause tachycardia, primarily due to increase in metabolic demands. An increase in sympathetic nervous system stimulation causes the heart rate to increase, both by the direct action of sympathetic nerve fibers on the heart and by causing the endocrine system to release hormones such as epinephrine (adrenaline), which have a similar effect. Increased sympathetic stimulation is usually due to physical or psychological stress.
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A sound processor behind the ear Bone-anchored hearing aids use a surgically implanted abutment to transmit sound by direct conduction through bone to the inner ear, bypassing the external auditory canal and middle ear. A titanium prosthesis is surgically embedded into the skull with a small abutment exposed outside the skin. A sound processor sits on this abutment and transmits sound vibrations to the titanium implant. The implant vibrates the skull and inner ear, which stimulate the nerve fibers of the inner ear, allowing hearing.
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In contrast, a patient over 60 years old with a cut nerve in the hand would expect to recover only protective sensation, that is, the ability to distinguish hot/cold or sharp/dull. Many other factors also affect nerve recovery. The use of autologous nerve grafting procedures that involve redirection of regenerative donor nerve fibers into the graft conduit has been successful in restoring target muscle function. Localized delivery of soluble neurotrophic factors may help promote the rate of axon regeneration observed within these graft conduits.
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A fundus photograph showing the back of the retina. The white circle is the beginning of the optical nerve. The optic nerve is composed of retinal ganglion cell axons and glial cells. Each human optic nerve contains between 770,000 and 1.7 million nerve fibers, which are axons of the retinal ganglion cells of one retina. In the fovea, which has high acuity, these ganglion cells connect to as few as 5 photoreceptor cells; in other areas of retina, they connect to many thousand photoreceptors.
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The sucrose gap technique was first introduced by in 1954 who worked with Alan Hodgkin and Andrew Huxley between 1947 and 1949. From his research, Stämpfli determined that currents moving along nerve fibers can be measured more easily when there is a gap of high resistance that reduces the amount of conducting medium outside of the cell. Stämpfli observed many problems with the ways that were being used to measure membrane potential at the time. He experimented with a new method that he called the sucrose gap.
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The pain pathway is mostly transmitted via myelinated Aδ (sharp or stabbing pain) and unmyelinated C nerve fibers (slow, dull, aching, or burning pain) of the trigeminal nerve, which supplies sensation to the teeth and gums via many divisions and branches. Initially, pain is felt while noxious stimuli are applied (such as cold). Continued exposure decreases firing thresholds of the nerves, allowing normally non- painful stimuli to trigger pain (allodynia). Should the insult continue, noxious stimuli produce larger discharges in the nerve, perceived as more intense pain.
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The gene is expressed in spindle-shaped cells located along nerve fibers between the auditory ganglion and sensory epithelium. These cells accompany neurites at the habenula perforata, the opening through which neurites extend to innervate hair cells. This and the pattern of expression of this gene in chicken inner ear paralleled the histologic findings of acidophilic deposits, consistent with mucopolysaccharide ground substance, in temporal bones from DFNA9 (autosomal dominant nonsyndromic sensorineural deafness 9) patients. Mutations that cause DFNA9 have been reported in this gene.
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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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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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The central zone is composed of the glial cells, neuronal cell bodies and a high density of fenestrated capillaries. Conversely, the rostral and caudal areas have a lower density of capillaries and are mostly made of nerve fibers, with fewer neurons and glial cells seen in this area. Functionally, however, the SFO may be viewed in two portions, the dorsolateral peripheral division, and the ventromedial core segment. The subfornical organ contains endothelin receptors mediating vasoconstriction and high rates of glucose metabolism mediated by calcium channels.
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This magnified image of type 2 muscle fibers shows denervation atrophy occurring at the white spaces at the top left and bottom center of the image. The white space represents a disruption of the nerve fibers, resulting in a loss of nerve supply to the muscle fibers. Denervation is any loss of nerve supply regardless of the cause. If the nerves lost to denervation are part of the neuronal communication to a specific function in the body then altered or a loss of physiological functioning can occur.
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There are several mechanisms of nerve injury including mechanical lesions, ischemia, immunologic attack, metabolic disorder, toxic agents, and exposure to radiation. The most common mechanism of injury is nerve compression in which external pressure causes decreased blood flow to the nerve and deformation of the nerve fibers. Repeated or prolonged compression of the nerve results in ischemia and ultimately edema above and below the source of the pressure (I). The thinning of myelin sheaths or focal demyelination are the main consequences of the injury that lead to conduction blockage.
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Acute optic neuritis (AON) is a disease which involves damage within the nerve fibers and loss of myelin within the optic nerve (it normally involves one eye and it's characterized by inflammation). One clinical trial studying the effects on BIIB033 on acute optic neuritis. Throughout the study, optic nerve conduction latency was measured (the time for a signal to travel from the retina to the brain's visual cortex). As about half of patients with optic neuritis will later develop multiple sclerosis, BIIB033 antibody treatment is also being considered for the former disease.
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The parenchymal syphilis, presents as tabes dorsalis and general paresis. Tabes dorsalis thought to be due to irreversible degeneration of nerve fibers in posterior columns of the spinal cord involving the lumbosacral and lower thoracic levels. The general paresis is caused by meningeal vascular inflammation and ependymal granulomatous infiltration may lead to neuronal loss, along with astrocytic and microglial proliferation and damage may preferentially occur in the cerebral cortex, striatum, hypothalamus, and meninges. Concurrent infection of T. pallidum with human immunodeficiency virus (HIV) has been found to affect the course of syphilis.
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Approximately 90% of released NE from the sympathetic nerve fibers is taken up again by postganglionic adrenergic neurons through the protein NET. The reuptake of NE is either repackaged into vesicles or degraded by the enzyme monoamine oxidase (MAO). The NET is located in the plasma membrane of noradrenergic neurons and serves as the fundamental mechanism by terminating the biological effects of NE in the synapse. The NE inactivation process, when taken up by the NET, is crucial in preventing too much increase in the NE concentration in the synaptic cleft.
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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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Blood vessels, lymphatic vessels, and nerves (all supplying the mucosa) will run through here. In the intestinal wall, tiny parasympathetic ganglia are scattered around forming the submucous plexus (or "Meissner's plexus") where preganglionic parasympathetic neurons synapse with postganglionic nerve fibers that supply the muscularis mucosae. Histologically, the wall of the alimentary canal shows four distinct layers (from the lumen moving out): mucosa, submucosa, muscularis externa, and a either a serous membrane or an adventitia. In the gastrointestinal tract and the respiratory tract the submucosa contains the submucosal glands that secrete mucus.
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Naegleria fowleri's human eye-like structure N. fowleri invades the central nervous system via the nose, specifically through the olfactory mucosa of the nasal tissues. This usually occurs as the result of the introduction of water that has been contaminated with N. fowleri into the nose during activities such as swimming, bathing or nasal irrigation. The amoeba follows the olfactory nerve fibers through the cribriform plate of the ethmoid bone into the skull. There, it migrates to the olfactory bulbs and subsequently other regions of the brain, where it feeds on the nerve tissue.
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The cephalic phase of digestion is the stage in which the stomach responds to the mere sight, smell, taste, or thought of food. About 20% of total acid secretion occurs before food enters the stomach. These sensory and mental inputs converge on the hypothalamus to induce the responses needed for preparing the gastrointestinal tract for food processing, which relays signals to the medulla oblongata. Vagus nerve fibers from the medulla stimulate the parasympathetic nervous system of the stomach which, in turn, stimulates gastric secretion (via parietal and G cells).
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The sacral sympathetic nerves arise from the sacral part of the sympathetic trunk, emerging anteriorly from the ganglia. They travel to their corresponding side's inferior hypogastric plexus, where the preganglionic nerve fibers synapse with the postganglionic sympathetic neurons, whose fibers ascend to the superior hypogastric plexus, the aortic plexus and the inferior mesenteric plexus, where they are distributed to the anal canal. From the inferior hypogastric plexus, they also innervate pelvic organs and vessels. The sacral sympathetic nerves contain a mix of preganglionic and postganglionic sympathetic fibers, but mostly preganglionic.
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Vittorio Marchi (1851-1908) Vittorio Marchi (30 May 1851, Novellara - 12 May 1908, Iesi) was an Italian neurologist and histologist. He studied pharmaceutical chemistry and medicine at the University of Modena, earning his doctorate in 1882.Vittorio Marchi in Dizionario Biografico – Treccani (biography) He was head of the histology laboratory at the psychiatric hospital of Reggio Emilia, and later director of the primary medical hospital in Iesi.Treccani.it Vittorio Marchi nell'Enciclopedia Treccani He was the creator of a popular osmium-based staining method ("Marchi stain") for the demonstration of degenerating nerve fibers.
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Stimulation of specialized pain-sensitive nerve fibers (nociceptors) that innervate bone tissue leads to the sensation of bone pain. Bone pain originates from both the periosteum and the bone marrow which relay nociceptive signals to the brain creating the sensation of pain. Bone tissue is innervated by both myelinated (A beta and A delta fiber) and unmyelinated (C fiber) sensory neurons. In combination, they can provide an initial burst of pain, initiated by the faster myelinated fibers, followed by a slower and longer-lasting dull pain initiated by unmyelinated fibers.
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Allozyne is a clinical stage biotechnology company headquartered in Seattle's biotech and high tech innovation corridor. Allozyne was founded in 2005 by California Institute of Technology researchers, and was incubated by Accelerator Corporation. Its lead product candidate, AZ01, is a long acting interferon beta for the treatment of the relapsing remitting form of multiple sclerosis, a chronic degenerative disease characterized by demyelination of nerve fibers leading to severe nerve damage and increasing disability. Multiple sclerosis is estimated to affect 400,000 individuals in the US alone and 2.5 million worldwide.
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An upper motor neuron lesion (also known as pyramidal insufficiency) occurs in the neural pathway above the anterior horn cell of the spinal cord or motor nuclei of the cranial nerves. Conversely, a lower motor neuron lesion affects nerve fibers traveling from the anterior horn of the spinal cord or the cranial motor nuclei to the relevant muscle(s). Upper motor neuron lesions occur in the brain or the spinal cord as the result of stroke, multiple sclerosis, traumatic brain injury, cerebral palsy, atypical parkinsonisms, multiple system atrophy, and amyotrophic lateral sclerosis.
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A physical examination will involve testing the deep ankle reflex as well as examining the feet for any ulceration. For large fiber neuropathy, an exam will usually show an abnormally decreased sensation to vibration, which is tested with a 128-Hz tuning fork, and decreased sensation of light touch when touched by a nylon monofilament. Diagnostic tests include electromyography (EMG) and nerve conduction studies (NCSs), which assess large myelinated nerve fibers. Testing for small-fiber peripheral neuropathies often relates to the autonomic nervous system function of small thinly- and unmyelinated fibers.
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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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They also receive input from efferent nerve fibers leading back to the same set of nerves. The entire cluster of cells is infiltrated with capillaries to provide access to the bloodstream; the high capillary density makes this one of the areas of the body with the greatest blood flow. Type I cells are densely packed with vesicles containing various neurotransmitters, including dopamine, ATP, serotonin, catecholamine, released during transduction. Type I cells are often connected via gap junctions, which might allow for quick communication between cells when transducing signals.
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The complex changes that the Schwann cell undergoes during the process of myelination of peripheral nerve fibers have been observed and studied by many. The initial envelopment of the axon occurs without interruption along the entire extent of the Schwann cell. This process is sequenced by the in-folding of the Schwann cell surface so that a double membrane of the opposing faces of the in-folded Schwann cell surface is formed. This membrane stretches and spirally wraps itself over and over as the in-folding of the Schwann cell surface continues.
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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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Hypothermia in cold environments also occurs. Intellectual disability of varying degree is observed in most affected individuals; hyperactivity and emotional lability are common. Hereditary sensory neuropathy type IV (HSN4) is a rare genetic disorder characterized by the loss of sensation (sensory loss), especially in the feet and legs and, less severely, in the hands and forearms. The sensory loss is due to abnormal functioning of small, unmyelinated nerve fibers and portions of the spinal cord that control responses to pain and temperature as well as other involuntary or automatic body processes.
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The cochlea is tonotopically mapped in a spiral fashion, with lower frequencies localizing at the apex of the cochlea, and high frequencies at the base of the cochlea, near the oval and round windows. With age, comes a loss in distinction of frequencies, especially higher ones. The electrodes of the implant are designed to stimulate the array of nerve fibers that previously responded to different frequencies accurately. It is important to note that due to spatial constraints, the cochlear implant may not be inserted all the way into the cochlear apex.
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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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With autopsies, the principal work of the neuropathologist is to help in the post-mortem diagnosis of various conditions that affect the central nervous system. Biopsies can also consist of the skin. Epidermal nerve fiber density testing (ENFD) is a more recently developed neuropathology test in which a punch skin biopsy is taken to identify small fiber neuropathies by analyzing the nerve fibers of the skin. This test is becoming available in select labs as well as many universities; it replaces the traditional nerve biopsy test as less invasive.
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Underneath the gray matter of the cortex lies white matter, made up largely of myelinated nerve fibers running to and from the cortex. Embedded within the white matter—which is sometimes called the arbor vitae (tree of life) because of its branched, tree-like appearance in cross- section—are four deep cerebellar nuclei, composed of gray matter. Connecting the cerebellum to different parts of the nervous system are three paired cerebellar peduncles. These are the superior cerebellar peduncle, the middle cerebellar peduncle and the inferior cerebellar peduncle, named by their position relative to the vermis.
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The habenular commissure, is a brain commissure (a band of nerve fibers) situated in front of the pineal gland that connects the habenular nuclei on both sides of the diencephalon. The habenular commissure is part of the habenular trigone (a small depressed triangular area situated in front of the superior colliculus and on the lateral aspect of the posterior part of the tænia thalami). The trigonum habenulæ also contains groups of nerve cells termed the ganglion habenulæ. Fibers enter the trigonum habenulæ from the stalk of the pineal gland, and the habenular commissure.
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Improvement indicates that the cause of lameness was from a structure desensitized by the nerve block. Nerve blocks are performed in a step-wise fashion, beginning at the most distal (lower) part of the limb and moving upward. This is due to the fact that blocking a nerve higher up will desensitize everything it innervates distal to the blocking location. For example, blocking the leg at the level of the fetlock will also block the entire foot, since the nerve fibers that innervate the foot are inhibited when they travel through the fetlock area.
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Santiago Ramón y Cajal, a Spanish anatomist, proposed that axons were the output components of neurons, describing their functionality. Joseph Erlanger and Herbert Gasser earlier developed the classification system for peripheral nerve fibers, based on axonal conduction velocity, myelination, fiber size etc. Alan Hodgkin and Andrew Huxley also employed the squid giant axon (1939) and by 1952 they had obtained a full quantitative description of the ionic basis of the action potential, leading to the formulation of the Hodgkin–Huxley model. Hodgkin and Huxley were awarded jointly the Nobel Prize for this work in 1963.
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Using a technique called microneurography, these investigators are able to record and measure neural activity in single nerve fibers of affected patients. By testing various hypotheses, these researchers hope to discover the unique mechanism that causes the spontaneous pain of CRPS, and that discovery may lead to new ways of blocking pain. Other studies to overcome chronic pain syndromes are discussed in the pamphlet "Chronic Pain: Hope Through Research", published by the NINDS. Research into treating the condition with mirror visual feedback is being undertaken at the Royal National Hospital for Rheumatic Disease in Bath.
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Kürten and Schmidt (1982) first suggested that the location and orientation of each pit structure provided directional information in infrared radiation detection. From their initial studies, the nasal pits seemed to be ideal for purposes of IR-perception. Later in 1984, Kürten and collaborators made electrophysiological recordings from nerve fibers of temperature-sensitive infrared thermoreceptors located on the central nose- leaf and upper lip, but did not find such receptors in the nasal pits (see Physiology). This revoked their earlier hypothesis and established that the infrared-sensitive receptors are located on the central nose-leaf.
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The subfornical organ is a sensory CVO situated on the underside of the fornix and lacking a BBB, the absence of which characterizes the circumventricular organs. Protruding into the third ventricle of the brain, the highly vascularized SFO can be divided into 3-4 anatomical zones, especially by its capillary density and structure. The central zone is composed exclusively of the glial cells and neuronal cell bodies. Conversely, the rostral and caudal areas are mostly made of nerve fibers while very few neurons and glial cells can be seen in this area.
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The sucrose gap technique is used to create a conduction block in nerve or muscle fibers. A high concentration of sucrose is applied to the extracellular space, which prevents the correct opening and closing of sodium and potassium channels, increasing resistance between two groups of cells. It was originally developed by Robert Stämpfli for recording action potentials in nerve fibers, and is particularly useful for measuring irreversible or highly variable pharmacological modifications of channel properties since untreated regions of membrane can be pulled into the node between the sucrose regions.
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The sucrose gap technique allows ion currents to be measured in multicellular tissues. Although voltage clamp and patch clamp methods are also effective in studying the functions of neurons, the sucrose gap technique is easier to perform and less expensive. Furthermore, the sucrose gap technique can provide stable recordings from small cells, such as nerve fibers or smooth muscle cells, for an extended period of time. It is very complicated, however, to achieve similar measurements with intracellular or patch-clamp electrodes because they can physically damage small axons or cells.
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The blood flow into pancreas is regulated by sympathetic nerve fibers, while parasympathetic neurons stimulate the activity of acinar and centroacinar cells. Pancreatic secretion is an aqueous solution of bicarbonate originating from the duct cells and enzymes originating from the acinar cells. The bicarbonate assists in neutralising the low pH of the chyme coming from the stomach, while the enzymes assist in the breakdown of the proteins, lipids and carbohydrates for further processing and absorption in the intestines. Pancreatic juice is secreted into the duodenum through duodenal papillae.
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The endoneurium (also called endoneurial channel, endoneurial sheath, endoneurial tube, or Henle's sheath) is a layer of delicate connective tissue around the myelin sheath of each myelinated nerve fiber in the peripheral nervous system. Its component cells are called endoneurial cells. The endoneuria with their enclosed nerve fibers are bundled into groups called nerve fascicles, each fascicle within its own protective sheath called a perineurium. In sufficiently large nerves multiple fascicles, each with its blood supply and fatty tissue, may be bundled within yet another sheath, the epineurium.
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It initiates immediate withdrawal of limbs or appendages, or the entire body, and therefore has clear adaptive advantages. Nociception usually involves the transmission of a signal along a chain of nerve fibers from the site of a noxious stimulus at the periphery to the spinal cord and brain. In vertebrates, this process evokes a reflex arc response generated at the spinal cord and not involving the brain, such as flinching or withdrawal of a limb. Nociception is found, in one form or another, across all major animal taxa.
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Muscle is arranged in two layers: one in which the muscle fibers run longitudinal to the esophagus, and the other in which the fibers encircle the esophagus. These are separated by the myenteric plexus, a tangled network of nerve fibers involved in the secretion of mucus and in peristalsis of the smooth muscle of the esophagus. The outermost layer of the esophagus is the adventitia in most of its length, with the abdominal part being covered in serosa. This makes it distinct from many other structures in the gastrointestinal tract that only have a serosa.
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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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Most of the space in the brain is taken up by axons, which are often bundled together in what are called nerve fiber tracts. A myelinated axon is wrapped in a fatty insulating sheath of myelin, which serves to greatly increase the speed of signal propagation. (There are also unmyelinated axons). Myelin is white, making parts of the brain filled exclusively with nerve fibers appear as light-colored white matter, in contrast to the darker-colored grey matter that marks areas with high densities of neuron cell bodies.
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Because chemoresponsive nerve fibers are present in all types of skin, chemesthetic sensations can be stimulated from anywhere on the body's surface as well as from mucosal surfaces in the nose, mouth, eyes, etc. Mucus membranes are generally more sensitive to chemesthetic stimuli because they lack the barrier function of cornified skin. Much of the chemesthetic flavor sensations are mediated by the trigeminal nerves, which are relatively large and important nerves. Flavors that stimulate the trigeminal nerves are therefore important - for example, carbon dioxide is the trigeminal stimulant in carbonated beverages.
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In his book, Why We Get Sick, Randolph Nesse uses the "blind spot" in the vertebrate eye (caused by the nerve fibers running through the retina) as an example of this. He argues that natural selection has come up with an elaborate work-around of the eyes wobbling back-and-forth to correct for this, but vertebrates have not found the solution embodied in cephalopod eyes, where the optic nerve does not interrupt the view. See also: Evolution of the eye. Another example is the cranial nerves in tetrapods.
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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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Warren Grill and J. Thomas Mortimer, may be observed in the adjacent image. Building upon this, a stimulus with two depolarizing prepulses, each of an amplitude slightly below the threshold current (at the time of delivery), should increase the radii of influence for nearby nerve fiber inactivation and distant nerve fiber excitation. Typically, nerve fibers of a larger diameter may be activated by single-pulse stimuli of a lower intensity, and thus may be recruited more readily. However, DPPs have demonstrated the additional capability to invert this recruitment order.
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In 1898, British scientist John Newport Langley first coined the term "autonomic" in classifying the connections of nerve fibers to peripheral nerve cells. Previous researchers had utilized different terms such as "the sympathetic nerves" [Winslow et al.] to describe the way in which neurons in one part of the body brought about sympathetic reactions in another part of the body, as well as the "ganglionic nerves and ganglionic nervous system" [Livingstone et al.] for the ganglionic conversion of voluntary to involuntary movements (which supposedly made these peripheral nerves 'ganglionic nerves'), among other classifications.
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The thalamus (from Greek θάλαμος, "chamber")Harper - index & University of Washington Faculty Web Server & Search engine search page + Perseus Project tufts.edu Retrieved 2012-02-09 is a large mass of gray matter located in the dorsal part of the diencephalon (a division of the forebrain). Nerve fibers project out of the thalamus to the cerebral cortex in all directions, allowing hub-like exchanges of information. It has several functions, such as relaying of sensory signals, including motor signals to the cerebral cortex and the regulation of consciousness, sleep, and alertness.
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Past research has shown that PRDM12 is involved in the modification of chromatin. Chromatin can turn genes off and on by attaching itself to chromosomes and acting as an epigenetic switch. Chromatin play a huge role in neuron development, so researcher hypothesized that mutations in the PRDM12 gene prevent nociceptors and nerve fibers from developing normally. They then studied the nerve biopsies of patients with this condition and found that the patients affected by this condition are lacking pain sensing never fibers in their legs, or only have half the amount they should have.
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Cranial: The upper and lower jaws are covered with sensory pits, visible as small, black speckles on the skin, the crocodilian version of the lateral line organs seen in fish and many amphibians, though arising from a completely different origin. These pigmented nodules encase bundles of nerve fibers innervated beneath by branches of the trigeminal nerve. They respond to the slightest disturbance in surface water, detecting vibrations and small pressure changes as small as a single drop. This makes it possible for crocodiles to detect prey, danger and intruders, even in total darkness.
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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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An energy deficiency in Schwann cells would account for the disappearance of myelin on peripheral nerves, which may result in damage to axons or loss of nerve function altogether. In peripheral nerves, oxidative enzyme activity is most concentrated around the nodes of Ranvier, making these locations most vulnerable to cofactor deprivation. Lacking essential cofactors reduces myelin impedance, increases current leakage, and slows signal transmission. Disruptions in conductance first affect the peripheral ends of the longest and largest peripheral nerve fibers because they suffer most from decreased action potential propagation.
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Neurapraxia occurs in the peripheral nervous system typically in the ulnar, median, and radial nerves of the upper body and in the sciatic and peroneal nerves of the lower body. Peripheral nerves are myelinated, relatively large, spatially complex cells whose size and connectivity typically make them more susceptible to damage and compromise their capacity to self-repair, although this is not the case in neurapraxia. Microscopic evidence has shown that there is damage to the myelin sheath, but not to the axon. Therefore, distal nerve fibers do not degenerate and the myelin damage can be repaired.
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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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The quality of the representation of a sound in the auditory nerve is limited by refractoriness, adaptation, saturation, and reduced synchronization (phase locking) at high frequencies, as well as by the stochastic nature of actions potentials. However, the auditory nerve contains thousands of fibers. Hence, despite these limiting factors, the properties of sounds are reasonably well represented in the population nerve response over a wide range of levels and audio frequencies (see Volley Theory). The coding of temporal information in the auditory nerve can be disrupted by two main mechanisms: reduced synchrony and loss of synapses and/or auditory nerve fibers.
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Optic nerve fibers from the retinas' nasal halves cross to the opposite sides joining the fibers from the temporal halves of the opposite retinas to form the optic tracts. The arrangements of the eyes' optics and the visual pathways mean vision from the left visual field is received by the right half of each retina, is processed by the right visual cortex, and vice versa. The optic tract fibers reach the brain at the lateral geniculate nucleus, and travel through the optic radiation to reach the visual cortex. Hearing and balance are both generated in the inner ear.
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The idea of the cortical homunculus was created by Wilder Penfield. Cortical stimulation mapping is used for somatotopy to determine the areas of the cerebral cortex that connect through nerve fibers with different body parts. Cortical stimulation identifies which regions of the brain are vital for certain functions, thereby allowing a 'map' to be made which can be used to decide if brain areas are safe to remove. Cortical stimulation mapping led to the development of a homunculus for the motor and sensory cortices, which is a diagram showing the brain's connections to different areas of the body.
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Immunologic hypotheses proposes that there may be differences in the antibodies in ocular MG versus generalized MG that may favor the muscles responsible for eye movement and eyelid elevation. Physiologic hypotheses propose that it is the unique structure and function of extraocular muscles that predispose them to weakness in MG. Compared to extremity muscles, extraocular muscles are smaller, served by more nerve fibers, and are among the fastest contracting muscles in the body. This higher level of activity may predispose them to fatigue in MG. Additionally, some reports indicate that there may be fewer acetylcholine receptors in extraocular muscles versus limb muscles.
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Meynert's work was largely focused on brain anatomy, pathology and histology, including the mapping of its intricate pathways and topography. He made many contributions involving the study of the cellular architecture of the brain and is often considered to be the founder of cerebral cortex cytoarchitectonics. Meynert developed theories in regards to correlations between neuroanatomical and mental processes. He conceptualized that a coupling between one mental association and its temporal successor as a literal contact between cortical nerve cells linked to one other by nerve fibers, and a series of cortical associations could therefore be construed as being a "train of thought".
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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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Cat hindlimb musculoskeletal model with redundant degrees of freedom at muscles (red lines) and joints One of the largest difficulties in motor control is quantifying the exact number of DOFs in the complex neuromuscular system of the human body. In addition to having redundant muscles and joints, muscles may span multiple joints, further complicating the system. Properties of muscle change as the muscle length itself changes, making mechanical models difficult to create and understand. Individual muscles are innervated by multiple nerve fibers (motor units), and the manner in which these units are recruited is similarly complex.
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Norepinephrine (NE), also known as noradrenaline, is a neurotransmitter that is released predominantly from the ends of sympathetic nerve fibers. The sympathetic nervous system is stimulated in fearful situations and elicits the “fight or flight” response both in animals and humans. This stimulus causes the release of catecholamines such as NE. The chemical class of catecholamines has positive chronotropic, inotropic and dromotropic effects which lead to increased heart rate, blood pressure and cardiac output. NE is one of the crucial neurotransmitters in the central nervous system (CNS) and plays an important role in regulating blood pressure, energy metabolism and controlling flexor muscles.
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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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Selumetinib was discovered by Array BioPharma and was licensed to AstraZeneca. It has been investigated for the treatment of various types of cancer, such as non-small cell lung cancer (NSCLC) and thyroid cancer. In April 2020, selumetinib was approved in the United States for the treatment of children with neurofibromatosis type 1 (NF1). Selumetinib is approved specifically for children who have symptomatic, inoperable plexiform neurofibromas (PN), which are tumors involving the nerve sheaths (coating around nerve fibers) and can grow anywhere in the body, including the face, extremities, areas around the spine and deep in the body where they may affect organs.
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Most LAs work on the internal surface of the membrane - the drug has to penetrate the cell membrane, which is achieved best in the nonionised form. Acidosis such as caused by inflammation at a wound partly reduces the action of LAs. This is partly because most of the anesthetic is ionized and therefore unable to cross the cell membrane to reach its cytoplasmic-facing site of action on the sodium channel. All nerve fibers are sensitive to LAs, but due to a combination of diameter and myelination, fibers have different sensitivities to LA blockade, termed differential blockade.
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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 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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Because the lumbar sympathetic nerve fibers control the muscle of the lower extremities during “fight or flight” response, treatment targeting this region can help relieve chronic leg pain. One common procedure is the lumbar sympathetic nerve block. This procedure involves an injection of an anesthetic in the sympathetic nerve tissue to block the sympathetic nerves ipsilaterally and test for any damage to the sympathetic nerve chain. By disrupting the nerve supply from the sympathetic chain to the lower extremities, monitoring the decrease of pain and swelling in these regions can help locate the origin of pain in the patient.
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As a result, an increased co-expression of multiple isoforms at demyelinating nodal sites in painful dental pulp. This isoforms of sodium channels may be a main factor in pain sensations due to their production of axonal excitability properties.Michael A Henry, et al, Unmyelinated nerve fibers in the human dental pulp express markers for myelinated fibers and show sodium channel accumulations, Neuroscience, Volume 169, Issue 4, 15 September 2010, Pages 1881-1887, ISSN 0306-4522, 10.1016/j.neuroscience.2010.06.044. Neuropeptides are increasingly being researched for having a role in molecular mechanisms involved with pain, including ion channels and inflammation.
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Non-synaptic transmission is characteristic of autonomic neuroeffector junctions. The essential features are that: the terminal portions of autonomic nerve fibers are varicose and mobile; transmitters are released from varicosities at varying distances from the effector cells; and while there is no structural post-junctional specialization on effector cells, receptors for neurotransmitters accumulate on cell membranes at close junctions. Besides smooth muscle, autonomic neural control of immune, epithelial, and endothelial cells also involves nonsynaptic transmission. Smooth muscle effectors are bundles rather than single cells, that are connected by gap junctions which allow electrotonic spread of activity between cells.
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This type of cell converts the event into an electrical signal by transduction. Several different types of nerve fibers carry out the transmission of the electrical signal from the transducing cell to the posterior horn of spinal cord, from there to the brain stem, and then from the brain stem to the various parts of the brain such as the thalamus and the limbic system. In the brain, the pain signals are processed and given context in the process of pain perception. Through modulation, the brain can modify the sending of further nerve impulses by decreasing or increasing the release of neurotransmitters.
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The microneurography technique allows the recording of impulse activity of individual nerve fibers with absolute resolution in attending human subjects. Hence the subject is able to cooperate in various kinds of tests while the exact and complete information carried by the individual nerve fiber is monitored and offered for analysis of correlations between neural activity and physical or mental events. On the other hand, the particular physical conditions involving a microelectrode freely floating in the tissue preclude brisk and large movements because the exact electrode position is easily jeopardized. The experiment is often time-consuming because the search procedure can be particularly demanding.
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The 1953 Science article mentioned above concluded that the reticular and regular collagenous materials contains the same four sugars – galactose, glucose, mannose, and fucose – but in a much greater concentration in the reticular than in the collagenous material. In a 1993 paper, the reticular fibers of the capillary sheath and splenic cord were studied and compared in the pig spleen by transmission electron microscopy. This paper attempted to reveal their components and the presence of sialic acid in the amorphous ground substance. Collagen fibrils, elastic fibers, microfibrils, nerve fibers, and smooth muscle cells were observed in the reticular fibers of the splenic cord.
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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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The output neurons of the DCN are pyramidal cells. They are glutamatergic, but also resemble Purkinje cells in some respects—they have spiny, flattened superficial dendritic trees that receive parallel fiber input, but they also have basal dendrites that receive input from auditory nerve fibers, which travel across the DCN in a direction at right angles to the parallel fibers. The DCN is most highly developed in rodents and other small animals, and is considerably reduced in primates. Its function is not well understood; the most popular speculations relate it to spatial hearing in one way or another.
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Stellate ganglion block also shows great potential as a means of reducing the number of hot flushes and night awakenings suffered by breast cancer survivors and women experiencing extreme menopause.Lancet, 2008 There has been interest in using Stellate Ganglion blocks to treat PTSD, particularly among combat veterans. A 2017 review of the evidence from the VA Evidence-based Synthesis Program found that while the procedure had been reported as effective in unblinded case series, the evidence from randomized controlled trials remained inconclusive. Nerve fibers from the Stellate Ganglion go up the superior cervical sympathetic chain and into the Pterygopalatine (Sphenopalatine) Ganglion (SPG).
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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 results from these two methods were combined and correlations were created between the electrical activity and visual responses to determine the different functions of the ganglion cells when prompted with a stimulus. Overall the new methods used in this study could help future studies publish detailed information about how optic nerve fibers work. In 1996, Baylor's article “How photons start vision” was published in the Proceedings of the National Academy of Sciences of the United States of America. This paper addressed the process of shutting down the transduction pathway that occurs in the response to light stimuli.
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The short ciliary nerve contains parasympathetic and sympathetic nerve fibers. The parasympathetics arise from the Edinger-Westphal nucleus and synapse in the ciliary ganglion via the oculomotor nerve, the postganglionic parasympathetics leave the ciliary ganglion in the short ciliary nerve and supply the ciliary body and iris. Sympathetics are provided by the superior cervical ganglion and they reach the ganglion either as branches of the nasociliary nerve or directly from the extension of the plexus on the ophthalmic artery (sympathetic branch to ciliary ganglion). Damage to the short ciliary nerve may result in loss of the pupillary light reflex, or mydriasis.
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In 1907, Louis Lapicque suggested that the action potential was generated as a threshold was crossed, what would be later shown as a product of the dynamical systems of ionic conductances. A great deal of study on sensory organs and the function of nerve cells was conducted by British physiologist Keith Lucas and his protege Edgar Adrian. Keith Lucas' experiments in the first decade of the twentieth century proved that muscles contract entirely or not at all, this was referred to as the all-or-none principle. Edgar Adrian observed nerve fibers in action during his experiments on frogs.
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Individuals with muscular weakness, occult instability, and decreased postural control are more susceptible to injury than those with better postural control. Instability leads to an increase in postural sway, the measurement of the time and distance a subject spends away from an ideal center of pressure. The measurement of a subject's postural sway can be calculated through testing center of pressure (CoP), which is defined as the vertical projection of center of mass on the ground. Investigators have theorized that if injuries to joints cause deafferentation, the interruption of sensory nerve fibers, and functional instability, then a subject's postural sway should be altered.
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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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Having cardiomyocytes connected via gap junctions allow all contractile cells of the heart to act in a coordinated fashion and contract as a unit. All the while being in sync with the pacemaker cells; this is the property that allows the pacemaker cells to control contraction in all other cardiomyocytes. Cells in the SA node spontaneously depolarize, ultimately resulting in contraction, approximately 100 times per minute. This native rate is constantly modified by the activity of sympathetic and parasympathetic nerve fibers via the autonomic nervous system, so that the average resting cardiac rate in adult humans is about 70 beats per minute.
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Corpus callosum view, front part at top of image Most people who are right- hand dominant have the left hemisphere of their brain specialize more in language processing. In terms of the mechanism of dyslexia, fMRI studies suggest that this specialization may be less pronounced or even absent in cases with dyslexia. Additionally, anatomical differences in the corpus callosum, the bundle of nerve fibers that connects the left and right hemispheres, have been linked to dyslexia via different studies. Data via diffusion tensor MRI indicate changes in connectivity or in gray matter density in areas related to reading/language.
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Electron microscopy and immunohistochemical staining analysis of teased nerve fibers shows that before macrophages arrive at the injury site, myelin is fragmented and myelin debris and lipid droplets are found in the cytoplasm of Schwann cells, indicating phagocytic activity before macrophages arrive. Schwann cell activity includes recruitment of macrophages to the injury site. Monocyte chemoattractant protein (MCP-1) plays a role in recruiting monocytes/macrophages. In tellurium-induced demylenation with no axon degeneration, nerve crush with axon degeneration, and nerve transection with axon degeneration an increase in MCP-1 mRNA expression followed by an increase in macrophage recruitment occurred.
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A motor neuron (or motoneuron) is a neuron whose cell body is located in the motor cortex, brainstem or the spinal cord, and whose axon (fiber) projects to the spinal cord or outside of the spinal cord to directly or indirectly control effector organs, mainly muscles and glands. There are two types of motor neuron – upper motor neurons and lower motor neurons. Axons from upper motor neurons synapse onto interneurons in the spinal cord and occasionally directly onto lower motor neurons. The axons from the lower motor neurons are efferent nerve fibers that carry signals from the spinal cord to the effectors.
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The major input to the cochlear nucleus is from the auditory nerve, a part of cranial nerve VIII (the vestibulocochlear nerve). The auditory nerve fibers form a highly organized system of connections according to their peripheral innervation of the cochlea. Axons from the spiral ganglion cells of the lower frequencies innervate the ventrolateral portions of the ventral cochlear nucleus and lateral-ventral portions of the dorsal cochlear nucleus. The axons from the higher frequency organ of corti hair cells project to the dorsal portion of the ventral cochlear nucleus and the dorsal-medial portions of the dorsal cochlear nucleus.
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During this time, the demand is high for sphingomyelin, which is made from phosphatidylcholine (and thus from choline), because this material is used to myelinate (insulate) nerve fibers. Choline is also in demand for the production of the neurotransmitter acetylcholine, which can influence the structure and organization of brain regions, neurogenesis, myelination, and synapse formation. Acetylcholine is even present in the placenta and may help control cell proliferation and differentiation (increases in cell number and changes of multiuse cells into dedicated cellular functions) and parturition. Choline uptake into the brain is controlled by a low-affinity transporter located at the blood–brain barrier.
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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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The ureteric plexus is a nerve plexus covering and innervating the ureter. The plexus can be graduated into three parts, as the ureter itself can be divided: In the upper part of the ureter, the plexus gets its nerve fibers mainly from the renal plexus, but also from the abdominal aortic plexus. In the intermediate part the plexus receives nervous input from the superior hypogastric plexus and in the lower part from the inferior hypogastric plexus. The plexus contains both sympathetic and parasympathetic fibers, where the sympathetic components come from T11 to L2 levels of the spinal cord.
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It has been shown that relaxation of carbachol-precontracted rat anococcygeous muscle occurs through the binding of bukatoxin to sodium channels, suggesting that bukatoxin has a muscle relaxation effect. Bukatoxin produces the effects by mediating the activation of nitrergic nerve fibers, most likely via an effect on presynaptic sodium channels.Srinivasan K.N., Nirthanana S, Sasakic T., Satoc K., Chengd B., Gweeb M.C.E., Kinie R.M., Gopalakrishnakonea P. (2001). Functional site of bukatoxin an α-type sodium channel neurotoxin from the Chinese scorpion (Buthus martensi Karsch) venom: probable role of 52PDKVP56 loop. FEBS Letters, 494, 145-149Goudeta C., Chib C.-W.
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In general, glomeruli receive input from ORs of one specific type and connect to the principal neurons of the OB, mitral and tufted cells (MT cells). Olfactory sensory neurons project axons to the brain within the olfactory nerve, (cranial nerveI). These nerve fibers, lacking myelin sheaths, pass to the olfactory bulb of the brain through perforations in the cribriform plate, which in turn projects olfactory information to the olfactory cortex and other areas. The axons from the olfactory receptors converge in the outer layer of the olfactory bulb within small (≈50 micrometers in diameter) structures called glomeruli.
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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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In 1811 in a self-sponsored and published pamphlet Charles Bell referred to the motor functions of nerve fibers exiting the ventral roots of the spinal cord but did not mention the sensory functions of the dorsal roots. That was in part because his studies were dissectionist and not vivisectionist; pain is elicited and detected best in a conscious animal. A dead, or rendered unconscious, animal would not produce the desired effect when posterior horn fibers, responsible for sensation and transfer of noxious signals, are stimulated. Bell's nephew, John Shaw travelled in 1812 to Paris where he presented Bell's system to the French anatomists.
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Several physiological factors may possibly influence the presence of F-waves after peripheral nerve stimulation. The shape and size of F-waves, along with the probability of their presence is small, as a high degree of variability exists in motor unit (MU) activation for any given stimulation. Thus, the generation of CMAP's which elicit F-waves is subject to the variability in activation of motor units in a given pool over successive stimuli. Moreover, stimulation of peripheral nerve fibers account for both orthodromic impulses (along sensory fibers, towards the dorsal horn), as well as antidromic activity (along alpha motor neurons towards the ventral horn).
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Anterograde and retrograde transneuronal degeneration is typically seen in humans around lesions in the limbic, visual, or dentate-rubro-olivary pathways. Lesions to the brain cause pathological changes that can cause anterograde transneuronal degeneration and lead to system degeneration. Brain lesions create structural or transient deafferntation (the interruption or elimination of sensory nerve impulses by injuring or damaging sensory nerve fibers) because injury to the area causes a loss of excitatory input to other areas in the brain, causing them to be less responsive to stimuli. Delayed secondary transneuronal degeneration can also occur at a late stage after brain injury because after the period of latency, neuroplastic rearrangement follows deafferentation.
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Normally, muscle contraction is a result of electrical signals sent from the central nervous system to muscle fibers via nerve impulses. At the neuromuscular junction, this electrical message is converted into a chemical message as acetylcholine is released from nerve fibers and attaches to corresponding receptors on the muscle fiber. In MG, antibodies are produced that block acetylcholine receptors, preventing the molecule from binding to the receptor and leading to a breakdown in communication between the nervous system and the muscle, resulting in muscle fatigue, and sometimes paralysis. Autoantibodies against acetylcholine receptors are detectable in 70–90% of patients with generalized MG, but only 50% in ocular MG.
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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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These retinal ganglion cells form a bundle at the optic disc, which is a part of the optic nerve. The two optic nerves from each eye meet at the optic chiasm, where nerve fibers from each nasal retina cross which results in the right half of each eye's visual field being represented in the left hemisphere and the left half of each eye's visual fields being represented in the right hemisphere. The optic tract then diverges into two visual pathways, the geniculostriate pathway and the tectopulvinar pathway, which send visual information to the visual cortex of the occipital lobe for higher level processing (Whishaw and Kolb, 2015).
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Ichiji Tasaki pioneered a thermodynamic approach to the phenomenon of nerve pulse propagation which identified several phenomena that were not included in the Hodgkin–Huxley model. Along with measuring various non electrical components of a nerve impulse, Tasaki investigated the physical chemistry of phase transitions in nerve fibers and its importance for nerve pulse propagation. Based on Tasaki's work, Konrad Kaufman proposed sound waves as a physical basis for nerve pulse propagation in an unpublished manuscript. The basic idea at the core of the soliton model is the balancing of intrinsic dispersion of the two dimensional sound waves in the membrane by nonlinear elastic properties near a phase transition.
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Neuroeffector junctions are known as neuromuscular junctions when the target cell is a muscle fiber. Non-synaptic transmission is characteristic of autonomic neuroeffector junctions. The structure of the autonomic neuromuscular junction consists of several essential features including that: the terminal portions of autonomic nerve fibers are varicose and mobile, transmitters being released ‘en passage’ from varying distances from the effector cells; while there is no structural post-junctional specialization on effector cells, receptors for neurotransmitters accumulate on cell membranes at close junctions. Muscle effectors are bundles rather than single smooth muscle cells that are connected by gap junctions which allow electrotonic spread of activity between cells.
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Sikozu Svala Shanti Sugaysi Shanu (called Sikozu), played by Raelee Hill, is a Kalish who grew up in Scarran- controlled space. She first appeared in "Crichton Kicks" and made her last appearance in "The Peacekeeper Wars Part 2". She becomes an expert (albeit a book expert) on Leviathans, and eventually goes to work for a pirate group who harvest toubray (nerve) fibers from Leviathans. She meets up with Crichton while he is aboard the Leviathan Elack in the Leviathan's sacred burial space; she led the pirates there and they subsequently try to kill her to prevent her telling anyone where the burial area is.
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Nervonic acid is particularly abundant in the white matter of animal brains and in peripheral nervous tissue where nervonyl sphingolipids are enriched in the myelin sheath of nerve fibers. In the same way, recent studies have concluded that nervonic acid is implicated as an intermediate in the biosynthesis of nerve cell myelin. This acid is an important member of the group of the cerebrosides, which are fatty acids of the glycosphingolipids group, important components of the muscles and the central nervous system and peripheral. Indeed, it is one of the major fatty acids in brain sphingolipids, normally accounting for approximately 40% of the total fatty acids in sphingolipids.
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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 corpus callosum, the band of nerve fibers, that connects the left and right hemispheres of the brain also gets affected in ASD. A study also found that 33% of people who suffered from AgCC (agenesis of the corpus callosum), a condition in which the corpus callosum is partially or completely absent, had scores higher than the autism screening cut-off. An ASD child’s brain grows at a very rapid rate and is almost fully grown by the age of 10. Recent fMRI studies have also found altered connectivity within the social brain areas due to ASD and may be related to the social impairments encountered in ASD.
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Upon returning to Japan he was appointed assistant professor of pathology at Kyushu Imperial University in Fukuoka, obtaining full professorship in 1908. :Node of Tawara: a remnant of primitive fibers found in all mammalian hearts at the base of the interauricular septum, and forming the beginning of the auriculoventricular bundle or bundle of His, which is a muscular band, containing nerve fibers, connecting the auricles with the ventricles of the heart. The Node of Tawara is also called the atrioventricular node, the auriculoventricular node, Aschoff's node, and the node of Aschoff and Tawara. Tawara's monograph, "Das Reizleitungssystem des Säugetierherzens" (English: "The Conduction System of the Mammalian Heart") was published in 1906.
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The membranous myelin sheath that surrounds and electrically insulates many nerve cell axons is particularly rich in sphingomyelin, suggesting its role as an insulator of nerve fibers. The plasma membrane of other cells is also abundant in sphingomyelin, though it is largely to be found in the exoplasmic leaflet of the cell membrane. There is, however, some evidence that there may also be a sphingomyelin pool in the inner leaflet of the membrane. Moreover, neutral sphingomyelinase-2 – an enzyme that breaks down sphingomyelin into ceramide - has been found to localise exclusively to the inner leaflet, further suggesting that there may be sphingomyelin present there.
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In the human gut they occur automatically when the resting membrane potential of the gastrointestinal smooth muscle becomes more positive than about -40 millivolts (the normal resting membrane potential in the smooth muscle fibers of the gut is between -50 and -60 millivolts). The spike potentials last 10 to 40 times as long in gastrointestinal muscle as the action potentials in large nerve fibers, each gastrointestinal spike lasting as long as 10 to 20 milliseconds.guyton - medical physiology 11th edition 2006, chapter-62, page-773 Conduction of nerve impulse, depolarization is the first stage of conduction. It occurs when the permeability of the cell membrane to sodium increases past a threshold.
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The aortic arch loops over the left pulmonary artery and the bifurcation of the pulmonary trunk, to which it remains connected by the ligamentum arteriosum, a remnant of the fetal circulation that is obliterated a few days after birth. In addition to these blood vessels, the aortic arch crosses the left main bronchus. Between the aortic arch and the pulmonary trunk is a network of autonomic nerve fibers, the cardiac plexus or aortic plexus. The left vagus nerve, which passes anterior to the aortic arch, gives off a major branch, the recurrent laryngeal nerve, which loops under the aortic arch just lateral to the ligamentum arteriosum.
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The peripheral olfactory system consists mainly of the nostrils, ethmoid bone, nasal cavity, and the olfactory epithelium (layers of thin tissue covered in mucus that line the nasal cavity). The primary components of the layers of epithelial tissue are the mucous membranes, olfactory glands, olfactory neurons, and nerve fibers of the olfactory nerves. Odor molecules can enter the peripheral pathway and reach the nasal cavity either through the nostrils when inhaling (olfaction) or through the throat when the tongue pushes air to the back of the nasal cavity while chewing or swallowing (retro-nasal olfaction). Inside the nasal cavity, mucus lining the walls of the cavity dissolves odor molecules.
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Action potential propagated by olfactory stimuli in an axon. Olfactory sensory neurons in the epithelium detect odor molecules dissolved in the mucus and transmit information about the odor to the brain in a process called sensory transduction. Olfactory neurons have cilia (tiny hairs) containing olfactory receptors that bind to odor molecules, causing an electrical response that spreads through the sensory neuron to the olfactory nerve fibers at the back of the nasal cavity. Olfactory nerves and fibers transmit information about odors from the peripheral olfactory system to the central olfactory system of the brain, which is separated from the epithelium by the cribriform plate of the ethmoid bone.
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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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The cochlear nuclear (CN) complex comprises two cranial nerve nuclei in the human brainstem, the ventral cochlear nucleus (VCN) and the dorsal cochlear nucleus (DCN). The ventral cochlear nucleus is unlayered whereas the dorsal cochlear nucleus is layered. Auditory nerve fibers, fibers that travel through the auditory nerve (also known as the cochlear nerve or eighth cranial nerve) carry information from the inner ear, the cochlea, on the same side of the head, to the nerve root in the ventral cochlear nucleus. At the nerve root the fibers branch to innervate the ventral cochlear nucleus and the deep layer of the dorsal cochlear nucleus.
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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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The sucking activates mechanoreceptors in and around the nipple. These signals are carried by nerve fibers through the spinal cord to the hypothalamus, where changes in the electrical activity of neurons that regulate the pituitary gland increase prolactin secretion. The suckling stimulus also triggers the release of oxytocin from the posterior pituitary gland, which triggers milk let-down: Prolactin controls milk production (lactogenesis) but not the milk-ejection reflex; the rise in prolactin fills the breast with milk in preparation for the next feed. In usual circumstances, in the absence of galactorrhea, lactation ceases within one or two weeks following the end of breastfeeding.
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Epineurial repair is a common surgical procedure to repair a nerve laceration via the epineurium, the connective tissue surrounding nerve fibers originating from the spinal cord. It is intended to allow the restoration of sensory function. When a nerve is lacerated or cut, repair is done by sewing the cut ends together through the epineurium to increase the potential of the proximal part growing correctly along the route the degrading distal part leaves behind. Usual sensation and mobility will not be an immediate result because nerves grow at a rate of approximately 1 millimeter per day, so it will take a few months to notice the final outcome.
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The cranial root of accessory nerve (or part) is the smaller of the two portions of the accessory nerve. It is generally considered as a part of the vagus nerve and not part of the accessory nerve proper because the cranial component rapidly joins the vagus nerve and serves the same function as other vagal nerve fibers. Recently, the concept of a cranial root of the accessory nerve has been challenged by new neuroanatomical studies which found that an unambiguous cranial root was not present in the majority of the cases.Anatomical evidence for the absence of a morphologically distinct cranial root of the accessory nerve in man.
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In terms of anatomy, an auditory nerve fiber is either bipolar or unipolar, with its distal projection being called the peripheral process, and its central projection being called the axon; these two projections are also known as the "peripheral axon" and the "central axon", respectively. The peripheral process is sometimes referred to as a dendrite, although that term is somewhat inaccurate. Unlike the typical dendrite, the peripheral process generates and conducts action potentials, which then "jump" across the cell body (or soma) and continue to propagate along the central axon. In this respect, auditory nerve fibers are somewhat unusual in that action potentials pass through the soma.
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The internal table of bone is thinner than the external table, and in some areas there is only a thin plate of compact bone with no diploë. Calvarial bones are supplied by endosteal and periosteal sheaths which are innervated by the nociceptors, sensory, sympathetic, and parasympathetic nerves. Horizontal section of the mouse pups showed that the density of nerve fibers was highest in the region of forehead, temples, and the back of head which crossing the frontal, parietal, and interparietal bones. In the calvarial innervation in the adult mouse, CGRP-labeled fibers and peripherin were seen in the sutures, emissary canals, and bone marrow but not in diploe.
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A technician can create different electrical distributions in the nerve to optimize the efficiency, and a patient controls the stimulation by passing a magnet over the unit. Some degree of facial numbness is expected after most of these surgical procedures, and neuralgia might return despite the procedure's initial success. Depending on the procedure, other surgical risks include hearing loss, balance problems, infection, and stroke. These surgeries include rhizotomy (where select nerve fibers are destroyed to block pain) and Microvascular decompression (where the surgeon moves the vessels that are compressing the nerve away from it and places a soft cushion between the nerve and the vessels).
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As an example, Leone et al. have placed the transcription unit under the control of the regulatory sequences of the myelin proteolipid protein (PLP) gene, leading to induced removal of targeted gene sequences in oligodendrocytes and Schwann cells. The specific DNA fragment recognized by Cre remains intact in cells, which do not express the PLP gene; this in turn facilitates empirical observation of the localized effects of genome alterations in the myelin sheath that surround nerve fibers in the central nervous system (CNS) and the peripheral nervous system (PNS). Selective Cre expression has been achieved in many other cell types and tissues as well.
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Nerve block or regional nerve blockade is any deliberate interruption of signals traveling along a nerve, often for the purpose of pain relief. Local anesthetic nerve block (sometimes referred to as simply "nerve block") is a short-term block, usually lasting hours or days, involving the injection of an anesthetic, a corticosteroid, and other agents onto or near a nerve. Neurolytic block, the deliberate temporary degeneration of nerve fibers through the application of chemicals, heat, or freezing, produces a block that may persist for weeks, months, or indefinitely. Neurectomy, the cutting through or removal of a nerve or a section of a nerve, usually produces a permanent block.
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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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For patients with glaucoma and optic nerve atrophy, existing retinal prostheses are not an option since the optic nerve is damaged, therefore a prosthesis using cortical stimulation is a remaining hope to offer some vision function. A cortical visual prosthesis is a promising subject of research because it targets neurons past the site of disease in most blind patients. However, significant challenges remain such as reproducibility in different patients, long-term effects of electrical stimulation, and the higher complexity of visual organization in the primary visual cortex versus that in the retina. Another site of research for a vision prosthesis using cortical stimulation is the optic nerve itself, which contains the nerve fibers responsible for the complete visual field.
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After earning his PhD in 1940, he accepted a postdoctoral fellowship, and later a teaching position at Yale. During his four years at Yale, Bullock worked at the Marine Biological Laboratory (MBL) at Woods Hole during the summers. Here he taught invertebrate zoology and their famous physiology course, and he studied nerve nets in coelenterates and the structure and physiology of giant nerve fibers in annelids. His studies on nerve nets lead him to be one of the first experimentalists to understand the value and importance of computational techniques for modeling and data analysis. In 1944 Bullock accepted a faculty position at the University of Missouri, where he taught medical students anatomy and physiology.
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It has been estimated that if the human cerebellar cortex could be completely unfolded it would give rise to a layer of neural tissue about 1 meter long and 10 centimeters wide—a total surface area of 500-1000 square cm, all packed within a volume of 100-150 cubic cm. Underneath the gray matter of the cortex lies white matter, made up largely of myelinated nerve fibers running to and from the cortex. Embedded within the white matter—which is sometimes called the arbor vitae (Tree of Life) in the cerebellum because of its branched, tree-like appearance—are four deep cerebellar nuclei. The cerebellum can be divided according to three different criteria: gross anatomical, phylogenetical, and functional.
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Noxious stimuli activate the endings of nociceptive C and A delta nerve fibers, which carry the signal to neurons in the dorsal horn of spinal cord. DNIC refers to the mechanism by which dorsal horn wide dynamic range neurons responsive to stimulation from one location of the body may be inhibited by noxious stimuli (such as heat, high pressure or electric stimulation) applied to another, remote location in the body. The inhibition is thought to originate in the brain, and is thought to affect both wide dynamic range and nociception-specific neurons in the dorsal horn. Studies investigating gender differences in DNIC have shown mixed results with the effect dependent upon experimental methodology and measurement method.
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CCK is synthesized and released by enteroendocrine cells in the mucosal lining of the small intestine (mostly in the duodenum and jejunum), called I cells, neurons of the enteric nervous system, and neurons in the brain. It is released rapidly into the circulation in response to a meal. The greatest stimulator of CCK release is the presence of fatty acids and/or certain amino acids in the chyme entering the duodenum. In addition, release of CCK is stimulated by monitor peptide (released by pancreatic acinar cells), CCK-releasing protein (via paracrine signalling mediated by enterocytes in the gastric and intestinal mucosa), and acetylcholine (released by the parasympathetic nerve fibers of the vagus nerve).
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Since 1942, scientists have discovered many more of the processes involved in the effect of stress upon the body, such as the region of the brain called the amygdala. The series of events by which a sensory stimulus is introduced to the mind, and the amygdala processes the emotion of fear which follows is called the "vision-to-fear pathway", or the "auditory-to-fear pathway", depending on the stimulus. The generally recognized sequence of events, as enumerated by Esther M. Sternberg, MD, in 2002, stands as follows: various chemicals and electrical impulses are released that are transmitted by nerve fibers. Simultaneously, hormones are excreted from the brain, adrenal and pituitary glands in response to stress on the system.
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Kujawa's research program aims to find out aging and noise exposure alter inner ear structures and functions, how genetic factors affect vulnerability to hearing loss, and how neural processes can be manipulated for purposes of treatment or prevention. Noise-induced and age-related hearing loss are the most common forms of hearing loss seen in adult patients and they often co-exist in the same patients. In collaboration with M. Charles Liberman and other researchers, Kujawa has examined the vulnerability of the synapses that connect hair cells in the cochlea to auditory nerve fibers. Their research has shown that cochlear synapses may be temporarily or permanently damaged from overexposure to intense sound.
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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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Axons are classified in two systems. The first one introduced by Erlanger and Gasser, grouped the fibers into three main groups using the letters A, B, and C. These groups, group A, group B, and group C include both the sensory fibers (afferents) and the motor fibres (efferents). The first group A, was subdivided into alpha, beta, gamma, and delta fibers — Aα, Aβ, Aγ, and Aδ. The motor neurons of the different motor fibers, were the lower motor neurons – alpha motor neuron, beta motor neuron, and gamma motor neuron having the Aα, Aβ, and Aγ nerve fibers respectively. Later findings by other researchers identified two groups of Aa fibers that were sensory fibers.
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Temperature threshold measurements were directly measured by stimulating nerve fibers of thermoreceptors in the nose-leaf and upper lip with a water-circulated brass thermode and recording the impulses/second at every 5 °C shift in temperature from 10 to 40 °C. These receptors have a threshold of 28 °C and a maximum temperature response to 40 °C, beyond which there was either no firing or an irregular firing pattern. This threshold is 8 °C lower compared to those of warm receptor in other species of mammals, which implies extreme sensitivity to heat. After stimulation of these receptors, there is a transient increase in impulse activity which quickly decays due to adaptation and thus strengthens temporal acuity.
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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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The olfactory foramina, also known as the cribriform foramina (cribr- is "a sieve" in Greek), is the grouping of holes located on the cribriform plate. The cribriform plate forms the roof of the nasal cavity, and the olfactory foramina are in the two depressions lateral to the median blade of the cribriform plate called the crista galli. There is a pair of olfactory bulbs of the brain that rest in these two depressions. These holes that make up the olfactory foramina allow passage for about 20 bundles of nerve fibers that make up the olfactory nerve, also known as Cranial Nerve I (CNI), from the nasal cavity to meet with the olfactory bulbs.
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The thermal radiation above a given threshold causes an increase in the temperature of the nerve fiber, resulting in stimulation of the nerve and subsequent firing, with increased temperature resulting in increased firing rate. The sensitivity of the nerve fibers is estimated to be >0.001 °C. The pit organ will adapt to a repeated stimulus; if an adapted stimulus is removed, there will be a fluctuation in the opposite direction. For example, if a warm object is placed in front of the snake, the organ will increase in firing rate at first, but after a while will adapt to the warm object and the firing rate of the nerves in the pit organ will return to normal.
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This is the basis of the basophilic part of the spectrum of Romanowski-Giemsa effect. If only synthetic Azure B and Eosin Y is used, it may serve as a standardized Giemsa stain; but, without methylene blue, the normal neutrophilic granules tend to overstain and look like toxic granules. On the other hand, if methylene blue is used it might help to give the normal look of neutrophil granules and may also enhance the staining of nucleoli and polychromatophilic RBCs (reticulocytes).Dacie and Lewis Practical Haematology 10th ed, p61 A traditional application of methylene blue is the intravital or supravital staining of nerve fibers, an effect first described by Paul Ehrlich in 1887.
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The celiac plexus or coeliac plexus, also known as the solar plexus because of its radiating nerve fibers, is a complex network of nerves (a nerve plexus) located in the abdomen, near where the celiac trunk, superior mesenteric artery, and renal arteries branch from the abdominal aorta. It is behind the stomach and the omental bursa, and in front of the crura of the diaphragm, on the level of the first lumbar vertebra. The plexus is formed in part by the greater and lesser splanchnic nerves of both sides, and fibers from the anterior and posterior vagal trunks. The celiac plexus proper consists of the celiac ganglia with a network of interconnecting fibers.
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Nerve tissue loss is associated with the more severe nerve injuries. 50-60% of sensory and motor neurons has been calculated from experiments after the use of nerve grafts Schwann cells form myelin, insulation to the nerve to allow better conduction along the axon, around the nerve fibers and secrete growth factors that play a major role in the regeneration process. The cells can align themselves to provide directional support to the regrowth of axons after injury and possibly increase the level of secretion of growth factors by being modified genetically. The time needed to grow and harvest the cells may be too long for less severe injury because it takes 10 weeks to culture or grow enough.
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Charles Sherrington, who was born in Great Britain in 1857, is famous for his work on the nerve synapse as the site of transmission of nerve impulses, and for his work on reflexes in the spinal cord. His research also led him to hypothesize that every muscular activation is coupled to an inhibition of the opposing muscle. He was awarded a Nobel Prize for his work in 1932 along with Lord Edgar Adrian who made the first physiological recordings of neural activity from single nerve fibers. Alan Hodgkin and Andrew Huxley (born 1914 and 1917, respectively, in Great Britain), are known for their collaborative effort to understand the production of action potentials in the giant axons of squid.
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In his 1664 Treatise of Man, René Descartes theorized that the body was more similar to a machine, and that pain was a disturbance that passed down along nerve fibers until the disturbance reached the brain. This theory transformed the perception of pain from a spiritual, mystical experience to a physical, mechanical sensation meaning that a cure for such pain could be found by researching and locating pain fibers within the bodies rather than searching for an appeasement for god. This also moved the center of pain sensation and perception from the heart to the brain. Descartes proposed his theory by presenting an image of a man's hand being struck by a hammer.
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Ronald Melzack and Patrick Wall introduced their "gate control" theory of pain in the 1965 Science article "Pain Mechanisms: A New Theory". The authors proposed that both thin (pain) and large diameter (touch, pressure, vibration) nerve fibers carry information from the site of injury to two destinations in the dorsal horn of the spinal cord: transmission cells that carry the pain signal up to the brain, and inhibitory interneurons that impede transmission cell activity. Activity in both thin and large diameter fibers excites transmission cells. Thin fiber activity impedes the inhibitory cells (tending to allow the transmission cell to fire) and large diameter fiber activity excites the inhibitory cells (tending to inhibit transmission cell activity).
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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 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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The authors proposed that both thin (pain) and large diameter (touch, pressure, vibration) nerve fibers carry information from the site of injury to two destinations in the spinal cord: transmission cells that carry the pain signal up to the brain, and inhibitory interneurons that impede transmission cell activity. Activity in both thin and large diameter fibers excites transmission cells. Thin fiber activity impedes the inhibitory cells (tending to allow the transmission cell to fire) and large diameter fiber activity excites the inhibitory cells (tending to inhibit transmission cell activity). So, the more large fiber (touch, pressure, vibration) activity relative to thin fiber activity at the inhibitory cell, the less pain is felt.
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The smooth muscular layer within the vagina has a weak contractive force that can create some pressure in the lumen of the vagina; much stronger contractive force, such as during childbirth, comes from muscles in the pelvic floor that are attached to the adventitia around the vagina. The lamina propria is rich in blood vessels and lymphatic channels. The muscular layer is composed of smooth muscle fibers, with an outer layer of longitudinal muscle, an inner layer of circular muscle, and oblique muscle fibers between. The outer layer, the adventitia, is a thin dense layer of connective tissue and it blends with loose connective tissue containing blood vessels, lymphatic vessels and nerve fibers that are between pelvic organs.
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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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Parasympathetic component of the glossopharyngeal nerve that innervates the ipsilateral parotid gland. Origin and central course The preganglionic nerve fibers originate in the inferior salivatory nucleus of the rostral medulla and travel anteriorly and laterally to exit the brainstem between the medullary olive and the inferior cerebellar peduncle with the other components of CN IX. Note: These neurons do not form a distinct nucleus visible on cross-section of the brainstem. The position indicated on the diagram is representative of the location of the cell bodies of these fibers. Intracranial course Upon emerging from the lateral aspect of the medulla, the visceral motor fibers join the other components of CN IX to enter the jugular foramen.
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The two basic types of sensation are touch- position and pain-temperature. Touch-position input comes to attention immediately, but pain-temperature input reaches the level of consciousness after a delay; when a person steps on a pin, the awareness of stepping on something is immediate but the pain associated with it is delayed. Touch- position information is generally carried by myelinated (fast-conducting) nerve fibers, and pain-temperature information by unmyelinated (slow- conducting) fibers. The primary sensory receptors for touch-position (Meissner’s corpuscles, Merkel's receptors, Pacinian corpuscles, Ruffini’s corpuscles, hair receptors, muscle spindle organs and Golgi tendon organs) are structurally more complex than those for pain-temperature, which are nerve endings.
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TFSn information in the auditory nerve may be used to encode the (audio) frequency of low-frequency sounds, including single tones and more complex stimuli such as frequency-modulated tones or steady- state vowels (see role and applications to speech and music). The auditory system goes to some length to preserve this TFSn information with the presence of giant synapses (End bulbs of Held) in the ventral cochlear nucleus. These synapses contact bushy cells (Spherical and globular) and faithfully transmit (or enhance) the temporal information present in the auditory nerve fibers to higher structures in the brainstem. The bushy cells project to the medial superior olive and the globular cells project to the medial nucleus of the trapezoid body (MNTB).
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Psychophysical studies have suggested that degraded TFS processing due to age and hearing loss may underlie some suprathreshold deficits, such as speech perception; however, debate remains about the underlying neural correlates. The strength of phase locking to the temporal fine structure of signals (TFSn) in quiet listening conditions remains normal in peripheral single-neuron responses following cochlear hearing loss. Although these data suggest that the fundamental ability of auditory-nerve fibers to follow the rapid fluctuations of sound remains intact following cochlear hearing loss, deficits in phase locking strength do emerge in background noise. This finding, which is consistent with the common observation that listeners with cochlear hearing loss have more difficulty in noisy conditions, results from reduced cochlear frequency selectivity associated with outer-hair-cell dysfunction.
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Using polyimide as the substrate, Lacour rolled 2D gold microelectrodes and microchannels into 3D channel bundles to fit around axons. These 3D electrode channel devices fixed to polymer substrates not only provide an innovative tool for in vivo guided axon regeneration but also set the stage for in vivo electrode implants that can communicate with multiple groups of nerve fibers, one day possibly enabling effective communication between a prosthetic and the human body. Lacour later began to experiment with different substrates with which to build stretchable electronics that are more compatible with biological systems in vivo. Instead of using rigid, inorganic materials, like silicon, Lacour tested the viability of using pulsed lasers to create diamond-like carbon microstructures on polydimethylsiloxane.
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Human nervous system consists of the central nervous system (CNS), which comprises the brain and spinal cord, and the peripheral nervous system (PNS) comprising the nerve fibers that branch off from the spinal cord to all parts of the body. Both parts of the nervous system are actively involved in communicating signals between various parts of the body to ensure the smooth and efficient transfer of information that controls and coordinates the movement of muscles, and regulates organ functions. Neurons, which form the elemental unit of the nervous system, receive messages from their dendrites, relay the information as an electrical signal down the axon and releases chemical messengers known as neurotransmitters, thus converting the electrical signal into a chemical signal.Fahrbach, S. E. (2013).
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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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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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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 "on" response could be due to excitation of the optic nerve in response to depolarizing photoreceptors, while the decline to steady-state potential could be a sign of synaptic inhibition, and the "off" activity could indicate release from light- promoted inhibition. The light-promoted "off" potentials were found to be sensitive to anesthesia by magnesium chloride, with repetitive "off" potentials eliminated within minutes of being introduced to the magnesium chloride solution. However, the light-promoted "on" potentials were not affected by the magnesium chloride and would continue firing over an hour after being immersed in the magnesium chloride solution. These results could indicate that nerve fibers that are responsible for "off" stimuli are regulated by chemical synapses, which can be inhibited by magnesium.
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Guided by Dr. Mid-Nite, Palmer planned to operate on King's brain, specifically the abnormal mass of nerve fibers leading from the auditory cortex to a growth on the side of the inferior colliculus, the supposed source of Brainwave's powers. While a member of Black Adam's group, Brainwave acted both maliciously and in a calculating fashion, seemingly being depicted as a supervillain again. His telepathy is also portrayed at being at a high point, as he is able to will the powerful Captain Marvel to turn back into young Billy Batson by forcing him to say "Shazam!" The source of these actions are found in Hank's brain, where Palmer encounters Mr. Mind, a Captain Marvel villain, who is feeding on Brainwave's growth.
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In the clinical setting, the function of the internode can only be explored by excitability studies (see Measurement). Experimental observations utilizing threshold measurements to assess excitability of myelinated nerve fibers have indicated that the function of regenerated internodes indeed remains persistently abnormal, with regenerated motor axons displaying increased rheobase and decreased chronaxie—changes that are consistent with abnormal active membrane properties. These studies have furthermore determined that activity-dependent conduction block in myelination was due to hyperpolarization, as well as abnormally increased Na+ currents and increased availability of fast K+ rectifiers. Listed below are findings on the changes in nerve excitability, and therefore the strength-duration time constant, that have been observed within several of the most pervasive nerve disorders.
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Some of the axons of the cells of the lateral nucleus, and possibly also of the medial nucleus, are continued upward through the inferior peduncle to the roof nuclei of the opposite side of the cerebellum, to which also other fibers of the vestibular root are prolonged without interruption in the nuclei of the medulla oblongata. A second set of fibers from the medial and lateral nuclei end partly in the tegmentum, while the remainder ascend in the medial longitudinal fasciculus to arborize around the cells of the nuclei of the oculomotor nerve. Fibers from the lateral vestibular nucleus also pass via the vestibulospinal tract, to anterior horn cells at many levels in the spinal cord, in order to co-ordinate head and trunk movements.
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The VNC contains ascending and descending neurons that relay information to and from the brain, motor neurons that project into the body and synapse onto muscles, sensory neurons that receive information from the body and environment, and interneurons that coordinate circuitry of all of these neurons. The neurons of the VNC are organized into segmental ganglia with the nerve cords running down the ventral ("belly", as opposed to back) plane of the organism. Ventral nerve cords from anterior to posterior (the thoracic and abdominal tagma in the arthropods) are made up of segmental ganglia that are connected by a tract of nerve fibers passing from one side to the other of the nerve cord called commissures. The complete system bears some likeness to a rope ladder.
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The longitudinal fissure plays a key role in corpus callosotomy, neurosurgery resulting in split brain, as it provides unobstructed access to the corpus callosum. Corpus callosotomy is one of the procedures used for pharmacologically treating intractable epilepsy cases, and it consists of the division of the nerve fibers running between the two hemispheres through the corpus callosum. A neurosurgeon separates the two hemispheres physically by pulling them apart with special tools, and cuts through either approximately two thirds of the fibers in the case of partial callosotomy, or the entirety in the case of complete callosotomy. Without the presence of longitudinal fissure, the corpus callosotomy procedure would be significantly more challenging and dangerous, as it would require the surgeon to navigate through densely connected cortical areas.
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Neurapraxia is a disorder of the peripheral nervous system in which there is a temporary loss of motor and sensory function due to blockage of nerve conduction, usually lasting an average of six to eight weeks before full recovery. Neurapraxia is derived from the word apraxia, meaning “loss or impairment of the ability to execute complex coordinated movements without muscular or sensory impairment”. This condition is typically caused by a blunt neural injury due to external blows or shock-like injuries to muscle fibers and skeletal nerve fibers, which leads to repeated or prolonged pressure buildup on the nerve. As a result of this pressure, ischemia occurs, a neural lesion results, and the human body naturally responds with edema extending in all directions from the source of the pressure.
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The parafovea is the intermediate belt, where the ganglion cell layer is composed of more than five layers of cells, as well as the highest density of cones; the perifovea is the outermost region where the ganglion cell layer contains two to four layers of cells, and is where visual acuity is below the optimum. The perifovea contains an even more diminished density of cones, having 12 per 100 micrometres versus 50 per 100 micrometres in the most central fovea. That, in turn, is surrounded by a larger peripheral area, which delivers highly compressed information of low resolution following the pattern of compression in foveated imaging. Approximately half the nerve fibers in the optic nerve carry information from the fovea, while the remaining half carry information from the rest of the retina.
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There are behavioral and physiological consequences of VGluT3 ablation because it modulates a wide range of neuronal and physiological processes like anxiety, mood regulation, impulsivity, aggressive behavior, pain perception, sleep–wake cycle, appetite, body temperature and sexual behavior. Certainly, no significant change was found in aggression and depression-like behaviors, but in contrast, the loss of VGluT3 resulted in a specific anxiety-related phenotype. The sensory nerve fibers have different ways to detect the pain hypersensivity throughout their sensory modalities and conduction velocities, but at the moment is still unknown which types of sensory is related to the different forms of inflammatory and neuropathic pain hypersensivity. In this case, Vesicular glutamate transporter 3 (VGluT3), have been implicated in mechanical hypersensitivity after inflammation, but their role in neuropathic pain still remains under debate.
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Patients with blindsight have damage to the system that produces visual perception (the visual cortex of the brain and some of the nerve fibers that bring information to it from the eyes) rather than to the underlying brain system controlling eye movements. The phenomenon shows how, after the more complex perception system is damaged, people can use the underlying control system to guide hand movements towards an object even though they cannot see what they are reaching for. Hence, visual information can control behavior without producing a conscious sensation. This ability of those with blindsight to act as if able to see objects that they are unconscious of suggests that consciousness is not a general property of all parts of the brain, but is produced by specialised parts of it.
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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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The specialized olfactory receptor neurons of the olfactory nerve are located in the olfactory mucosa of the upper parts of the nasal cavity. The olfactory nerves consist of a collection of many sensory nerve fibers that extend from the olfactory epithelium to the olfactory bulb, passing through the many openings of the cribriform plate, a sieve-like structure of the ethmoid bone. The sense of smell arises from the stimulation of receptors by small molecules in inspired air of varying spatial, chemical, and electrical properties that reach the nasal epithelium in the nasal cavity during inhalation. These stimulants are transduced into electrical activity in the olfactory neurons, which then transmit these impulses to the olfactory bulb and from there they reach the olfactory areas of the brain via the olfactory tract.
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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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"Friction massage" uses surface pressure to causes temporary ischemia and subsequent hyperemia in the muscles, and this is hypothesized to inactivate trigger points and disrupt small fibrous adhesions within the muscle that have formed following surgery or muscular shortening due to restricted movement. Occasionally physiotherapy for TMD may include the use of transcutaneous electrical nerve stimulation (TENS), which may override pain by stimulation of superficial nerve fibers and lead to pain reduction which extends after the time where the TENS is being actually being applied, possibly due to release of endorphins. Others recommend the use of ultrasound, theorized to produce tissue heating, alter blood flow and metabolic activity at a level that is deeper than possible with surface heat applications. There is tentative evidence that low level laser therapy may help with pain.
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The Schwann cell promoter is present in the downstream region of the human dystrophin gene that gives shortened transcript that are again synthesized in a tissue-specific manner. During the development of the PNS, the regulatory mechanisms of myelination are controlled by feedforward interaction of specific genes, influencing transcriptional cascades and shaping the morphology of the myelinated nerve fibers. Schwann cells are involved in many important aspects of peripheral nerve biology—the conduction of nervous impulses along axons, nerve development and regeneration, trophic support for neurons, production of the nerve extracellular matrix, modulation of neuromuscular synaptic activity, and presentation of antigens to T-lymphocytes. Charcot–Marie–Tooth disease, Guillain–Barré syndrome (acute inflammatory demyelinating polyradiculopathy type), schwannomatosis, chronic inflammatory demyelinating polyneuropathy, and leprosy are all neuropathies involving Schwann cells.
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The anterior spinal artery arises bilaterally as two small branches near the termination of the vertebral arteries which descend anterior to the medulla and unite at the level of the foramen magnum. The infarction (which arises in the paramedian branches of the anterior spinal artery and/or the vertebral arteries) leads to death of the ipsilateral medullary pyramid, the medial lemniscus, and the hypoglossal nerve fibers that pass through the medulla. The spinothalamic tract is spared because it is located more laterally in the brainstem and is not supplied by the anterior spinal artery, but rather by the vertebral and posterior inferior cerebellar arteries. The trigeminal nucleus is also spared, since most of it is higher up in the pons, and the spinal part of it found in the medulla is lateral to the infarct.
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The trigeminal nerve (the fifth cranial nerve, or simply CN V) is a nerve responsible for sensation in the face and motor functions such as biting and chewing; it is the most complex of the cranial nerves. Its name ("trigeminal" = tri-, or three, and - geminus, or twin: thrice-twinned) derives from the fact that each of the two nerves (one on each side of the pons) has three major branches: the ophthalmic nerve (V1), the maxillary nerve (V2), and the mandibular nerve (V3). The ophthalmic and maxillary nerves are purely sensory, whereas the mandibular nerve supplies motor as well as sensory (or "cutaneous") functions. Adding to the complexity of this nerve is the fact that autonomic nerve fibers as well as special sensory fibers (taste) are contained within it.
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200x200px The thalamus is a paired structure of gray matter located in the forebrain which is superior to the midbrain, near the center of the brain, with nerve fibers projecting out to the cerebral cortex in all directions. The medial surface of the thalamus constitutes the upper part of the lateral wall of the third ventricle, and is connected to the corresponding surface of the opposite thalamus by a flattened gray band, the interthalamic adhesion. The lateral part of the thalamus is the phylogenetically newest part of the thalamus (neothalamus), and includes the lateral nuclei, the pulvinar and the medial and lateral geniculate nuclei. There are areas of white matter in the thalamus including the stratum zonale that covers the dorsal surface, and the external and internal medullary laminae.
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All the oculomotor muscles innervated by the third nerve may be affected, but those that control pupil size are usually well-preserved early on. This is because the parasympathetic nerve fibers within CNIII that influence pupillary size are found on the periphery of the nerve (in terms of a cross-sectional view), which makes them less susceptible to ischemic damage (as they are closer to the vascular supply). The sixth nerve, the abducens nerve, which innervates the lateral rectus muscle of the eye (moves the eye laterally), is also commonly affected but fourth nerve, the trochlear nerve, (innervates the superior oblique muscle, which moves the eye downward) involvement is unusual. Damage to a specific nerve of the thoracic or lumbar spinal nerves can occur and may lead to painful syndromes that mimic a heart attack, gallbladder inflammation, or appendicitis.
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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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Loss of aqueous humor absorption leads to increased resistance and thus a chronic, painless buildup of pressure in the eye. In close/narrow-angle, the iridocorneal angle is completely closed because of forward displacement of the final roll and root of the iris against the cornea, resulting in the inability of the aqueous fluid to flow from the posterior to the anterior chamber and then out of the trabecular network. This accumulation of aqueous humor causes an acute increase in pressure and pain. The inconsistent relationship of glaucomatous optic neuropathy with increased intraocular pressure has provoked hypotheses and studies on anatomic structure, eye development, nerve compression trauma, optic nerve blood flow, excitatory neurotransmitter, trophic factor, retinal ganglion cell/axon degeneration, glial support cell, immune system, aging mechanisms of neuron loss, and severing of the nerve fibers at the scleral edge.
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The retinal nerve fiber layer (RNFL) or nerve fiber layer, stratum opticum, is formed by the expansion of the fibers of the optic nerve; it is thickest near the optic disc, gradually diminishing toward the ora serrata. As the nerve fibers pass through the lamina cribrosa sclerae they lose their medullary sheaths and are continued onward through the choroid and retina as simple axis-cylinders. When they reach the internal surface of the retina they radiate from their point of entrance over this surface grouped in bundles, and in many places arranged in plexuses. Most of the fibers are centripetal, and are the direct continuations of the axis-cylinder processes of the cells of the ganglionic layer, but a few of them are centrifugal and ramify in the inner plexiform and inner nuclear layers, where they end in enlarged extremities.
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Roboz-Einstein, as well as Karian Kies at the National Institute of Health's NIMH, identified myelin basic protein (MBP) as being the antigen responsible for inciting the immune response in experimental allergic encephalomyelitis (EAE), a model system used to study multiple sclerosis (MS) and other demyelinating diseases. Scientists had known that they could produce an autoimmune response that led to encephalitis and demyelination (degradation of the fatty sheath called myelin that insulates nerve fibers) by injecting animals with nervous tissue, but before then they didn't know what specifically in this tissue was inciting the immune response. Roboz-Einstein and Kies were able to purify MBP and show it caused EAE. This discovery allowed Roboz-Einstein and other scientists to narrow down which specific regions of the protein were antigenic, leading to an improved model system and research on potential immunotherapies for demyelinating diseases.
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In the human brainstem, the solitary nucleus (SN) (nucleus of the solitary tract, nucleus solitarius, nucleus tractus solitarii) is a series of purely sensory nuclei (clusters of nerve cell bodies) forming a vertical column of grey matter embedded in the medulla oblongata. Through the center of the SN runs the solitary tract, a white bundle of nerve fibers, including fibers from the facial, glossopharyngeal and vagus nerves, that innervate the SN. The SN projects to, among other regions, the reticular formation, parasympathetic preganglionic neurons, hypothalamus and thalamus, forming circuits that contribute to autonomic regulation. Cells along the length of the SN are arranged roughly in accordance with function; for instance, cells involved in taste are located In the rostrum part, while those receiving information from cardio-respiratory and gastrointestinal processes are found in the caudal part.
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The cells of the ventral cochlear nucleus extract information that is carried by the auditory nerve in the timing of firing and in the pattern of activation of the population of auditory nerve fibers. The cells of the dorsal cochlear nucleus perform a non-linear spectral analysis and place that spectral analysis into the context of the location of the head, ears and shoulders and that separate expected, self-generated spectral cues from more interesting, unexpected spectral cues using input from the auditory cortex, pontine nuclei, trigeminal ganglion and nucleus, dorsal column nuclei and the second dorsal root ganglion. It is likely that these neurons help mammals to use spectral cues for orienting toward those sounds. The information is used by higher brainstem regions to achieve further computational objectives (such as sound source location or improvement in signal to noise ratio).
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Though e-Dura already substantially progressed the field towards effective neuroprosthetics, one major limiting factor that still remains is the ability to precisely record neural activity in order to seamlessly integrate the internal motivation and neural activity in an organism with the desired output of the prosthetic. In a therapeutic setting, the desired output of a neuroprosthetic can encompass a range of things from motor activity, such as driving muscles to fire and limbs to move, to silencing pain in chronic pain patients, to enabling amputees with the sensation of touch again. As such, Lacour and her team developed a “nerve- on-a-chip” platform that is able to stimulate and record neural activity in nerve fibers. Astonishingly, their technology, consisting of microfabricated electrode arrays, is able to record up to hundreds of individual neurons with a resolution at the level of individual neurons.
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For non-human primates and all non-human mammalian species the growth of the first permanent molar marks the end of lactation and the beginning of foraging, setting an early requirement for independence. Human children, on the other hand, do not have an advanced motor control capable of foraging and also lack the digestive capacity for unprepared food, and so have always relied on the active involvement of their mother and other caregivers in their care into childhood. The pre-frontal cortex, which is responsible for higher cognitive functions such as planning, decision-making, judgment and reasoning, develops and matures most rapidly during early adolescence and into the early 20s. Accompanying the growth of the pre-frontal cortex is continued synaptic pruning (the trimming of rarely used synapses) as well as increased myelination of nerve fibers in the brain, which serves to insulate and speed up signal transmission between neurons.
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The lamina cribrosa is thought to help maintain the pressure gradient between the inside of the eye and the surrounding tissue.Optic disc histomorphometry in normal eyes and eyes with secondary angle-closure glaucoma by J.B. Jonas; K.A. Koenigsreuther; G.O.H Naumann in Graefe's Archive for Clinical and Experimental Ophthalmology 1992; 230:134-139 Being structurally weaker than the much thicker and denser sclera, the lamina cribrosa is more sensitive to changes in the intraocular pressure and tends to react to increased pressure through posterior displacement. This is thought to be one of the causes of nerve damage in glaucoma, as the displacement of the lamina cribrosa causes the pores to deform and pinch the traversing nerve fibers and blood vessels.Three dimensional analysis of the lamina cribrosa in glaucoma by J Morgan-Davies; N Taylor; A R Hill; P Aspinall; C J O’Brien; A Azuara-Blanco in Br J Ophthalmol.
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He achieved a breakthrough during a vacation at the beach; he conceptualised using a seashell to replicate the human cochlea, and grass blades (which were flexible at the tip and gradually increasing in stiffness) to represent electrodes. Clark showed that the electrode bundle had to be free-fitting, and the wires needed to be terminated with circumferential bands to reduce friction against the outer wall of the cochlea, and so make it easier to pass the required distance. The bands had to be wide enough to minimise the charge density of the electric current for safety, but narrow enough for localised stimulation of the nerve fibers for the place coding of frequency. In order to address issues about the safety of the device, Clark conducted experiments to show that there was a minimal risk of meningitis from a middle ear infection if a fibrous tissue sheath grew around the electrode bundle.
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An infection may then predispose those people to develop IC. Current evidence from clinical and laboratory studies confirms that mast cells play a central role in IC/BPS possibly due to their ability to release histamine and cause pain, swelling, scarring, and interfere with healing. Research has shown a proliferation of nerve fibers is present in the bladders of people with IC which is absent in the bladders of people who have not been diagnosed with IC. Regardless of the origin, most people with IC/BPS struggle with a damaged urothelium, or bladder lining. When the surface glycosaminoglycan (GAG) layer is damaged (via a urinary tract infection (UTI), excessive consumption of coffee or sodas, traumatic injury, etc.), urinary chemicals can "leak" into surrounding tissues, causing pain, inflammation, and urinary symptoms. Oral medications like pentosan polysulfate and medications placed directly into the bladder via a catheter sometimes work to repair and rebuild this damaged/wounded lining, allowing for a reduction in symptoms.
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As described in the article Nociception, nociception is the sensory nervous system's response to harmful stimuli, such as a toxic chemical applied to a tissue. In nociception, chemical stimulation of sensory nerve cells called nociceptors produces a signal that travels along a chain of nerve fibers via the spinal cord to the brain. Nociception triggers a variety of physiological and behavioral responses and usually results in a subjective experience, or perception, of pain. Work by Pan et al. first showed that TET1 and TET3 proteins are normally present in the spinal cords of mice. They used a pain inducing model of intra plantar injection of 5% formalin into the dorsal surface of the mouse hindpaw and measured time of licking of the hindpaw as a measure of induced pain. Protein expression of TET1 and TET3 increased by 152% and 160%, respectively, by 2 hours after formalin injection. Forced reduction of expression of TET1 or TET3 by spinal injection of Tet1-siRNA or Tet3-siRNA for three consecutive days before formalin injection alleviated the mouse perception of pain.
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They contain sets of muscles that are common to all Acanthocephala including a proboscis receptacle, a receptacle- surrounding muscle called a receptacle protrusor, retinacula (connective tissue that stabilizes tendons), a neck retractor, proboscis and receptacle retractors, circular and longitudinal musculature under the metasomal (trunk) tegument, and a single muscular layer beneath the proboscis wall. Two regions of musculature are considerably different in Apororhynchus compared to the other acanthocephalan orders: the proboscis receptacle and receptacle protrusor are both reorganized in Apororhynchus with the muscles subdivided into strands extending from the cerebral ganglion, or nerve bundle, to the proboscis wall. These two muscles suspend the cerebral ganglion but are not involved in the eversion of the proboscis. Additional anatomical features that can be used to distinguish this genus among other acanthocephalans include a cerebral ganglion located under the anterior wall of the proboscis, long and tubular lemnisci (bundles of sensory nerve fibers) that run along a central canal, the lack of any protonephrida (an organ which functions as a kidney), and the presence of eight pear-shaped cement glands used to temporarily close the posterior end of the female after copulation.
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From 2000 until 2005 Gasson headed research to invasively interface the nervous system of a human to a computer. In 2002 a microelectrode array was implanted in the median nerve of a healthy human and connected percutaneously to a bespoke processing unit to allow stimulation of nerve fibers to artificially generate sensation perceivable by the subject and recording of local nerve activity to form control commands for wirelessly connected devices. During clinical evaluation of the implant, the nervous system of the human subject, Kevin Warwick, was connected onto the internet in Columbia University, New York enabling a robot arm, developed by Peter Kyberd, in the University of Reading UK to use the subject's neural signals to mimic the subject's hand movements while allowing the subject to perceive what the robot touched from sensors in the robot's finger tips. Further studies also demonstrated a form of extra sensory input and that it was possible to communicate directly between the nervous systems of two individuals, the first direct and purely electronic communication between the nervous systems of two humans, with a view to ultimately creating a form of telepathy or empathy using the Internet to communicate 'brain-to-brain'.
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