"If you're tall, it means you've got longer levers, so you can store energy over a greater amount of time, and that allows you to summate your forces over a greater distance," Kovacs says.
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These simple models accounted for neural summation (i.e., potentials at the post-synaptic membrane will summate in the cell body). Later models also provided for excitatory and inhibitory synaptic transmission.
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Temporal summation occurs when a high frequency of action potentials in the presynaptic neuron elicits postsynaptic potentials that summate with each other. The duration of a postsynaptic potential is longer than the interval between action potentials. If the time constant of the cell membrane is sufficiently long, as is the case for the cell body, then the amount of summation is increased. The amplitude of one postsynaptic potential at the time point when the next one begins will algebraically summate with it, generating a larger potential than the individual potentials.
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When a whole body is irradiated uniformly only the radiation weighting factor WR is used, and the effective dose equals the whole body equivalent dose. But if the irradiation of a body is partial or non-uniform the tissue factor WT is used to calculate dose to each organ or tissue. These are then summed to obtain the effective dose. In the case of uniform irradiation of the human body, these summate to 1, but in the case of partial or non-uniform irradiation, they will summate to a lower value depending on the organs concerned; reflecting the lower overall health effect.
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Thus, during a 100 Hz stimulus train, each EPSP will add to the membrane depolarization caused by the previous EPSPs. This synaptic summation drives the membrane potential toward values that could not be reached with single synaptic stimuli. As the EPSPs summate, they will exceed the spike threshold.
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As long as the membrane potential is below threshold for firing impulses, the membrane potential can summate inputs. That is, if the neurotransmitter at one synapse causes a small depolarization, a simultaneous release of transmitter at another synapse located elsewhere on the same cell body will summate to cause a larger depolarization. This is called spatial summation and is complemented by temporal summation, wherein successive releases of transmitter from one synapse will cause progressive polarization change as long as the presynaptic changes occur faster than the decay rate of the membrane potential changes in the postsynaptic neuron. Neurotransmitter effects last several times longer than presynaptic impulses, and thereby allow summation of effect.
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If only part of the body is irradiated, then only those regions are used to calculate the effective dose. The tissue weighting factors summate to 1.0, so that if an entire body is radiated with uniformly penetrating external radiation, the effective dose for the entire body is equal to the equivalent dose for the entire body.
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Depending on the species, there are typically one or two classes of horizontal cells, with a third type sometimes proposed. Horizontal cells span across photoreceptors and summate inputs before synapsing onto photoreceptor cells. Horizontal cells may also synapse onto bipolar cells, but this remains uncertain. There is a greater density of horizontal cells towards the central region of the retina.
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Slow wave potential are unstable resting membrane potentials that continuously cycle through depolarization- and repolarization phases. However, not every cycle reaches depolarization threshold and thus an action potential (AP) will not always fire. Owing to temporal summation (depolarization potentials spaced closely together in time so that they summate), however, cell membrane depolarization will periodically reach depolarization threshold and an action potential will fire, triggering contraction of the myocyte.
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Alike to the "Primary' section, accumulative points are awarded for the completion of questions in activities. Secondary Students also have access to 'Topic Tests' which summate the most difficult questions of the topic. The "Secondary Students" section of the website is also reachable on a Tablet device, and can be accessed for offline use. The same process of offline synchronisation to the online profile is also applied in the 'Secondary Students" section of the website.
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PKMzeta makes a great model for the de novo protein synthesis hypothesis. The effects of LTP summate to allow PKMzeta to be transcribed, which requires ribosomal activity in the dendrites (Sacktor, 2011). Blocking translation or transcription of proteins would prevent PKMzeta from being expressed, preventing the strengthening of neuronal networks that underlie a memory (Hawkins, Kandel, & Bailey, 2006). Because of its long half life, the maintenance of receptors at a synapse is not affected by PSI (Sacktor, 2011).
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A pathway may also be inhibited; removal of inhibitory input constitutes disinhibition, which, if other sources of excitation are present in the inhibitory input, can augment excitation. When a given target neuron receives inputs from multiple sources, those inputs can be spatially summated if the inputs arrive closely enough in time that the influence of the earliest-arriving inputs has not yet decayed. If a target neuron receives input from a single axon terminal and that input occurs repeatedly at short intervals, the inputs can summate temporally.
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A current with a reversal potential below threshold, such as a typical K+ current, is considered inhibitory. A current with a reversal potential above the resting potential, but below threshold, will not by itself elicit action potentials, but will produce subthreshold membrane potential oscillations. Thus, neurotransmitters that act to open Na+ channels produce excitatory postsynaptic potentials, or EPSPs, whereas neurotransmitters that act to open K+ or Cl− channels typically produce inhibitory postsynaptic potentials, or IPSPs. When multiple types of channels are open within the same time period, their postsynaptic potentials summate (are added together).
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Fairbairn's structural model is the beginning stage of a multiple personality, however it never develops beyond this steady state. As described, the central ego develops in relationship to the supportive and nurturing parent(s), the Ideal Object(s). The strength and size of the Central Ego varies from child to child according to how many positive, ego enhancing activities and interpersonal events they have experienced with their parents during the course of their development. Fairbairn's model assumes that actual events in the external world are internalized and summate in both the conscious central ego and in the unconscious structures as well.
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Coal is supplied via north- and south-facing junctions off the adjacent Manchester and Cleethorpes railway line. Coal arriving at the station is discharged from the permanently coupled 29.03-tonne-capacity (32 tons) hopper wagons, the bottoms of which are opened by automatic lineside gear while the train moves through at 0.8 km/h (0.5 mph). The four W & T Avery Ltd. weighbridges, two on each of the two rail tracks using electronic weighing heads, record the weight of the coal wagons loaded and empty and summate the total quantity of coal delivered. The coal store on the site has a maximum capacity of 1,814,000 tonnes (2 million tons) at 9.14 m (30 ft) deep, it is used to deposit all surplus coal and to build up stocks.
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