query: where are graded potentials generated in nerve cells

pos: Graded potential Graded potential Graded potentials are changes in membrane potential that vary in size, as opposed to being all-or-none. They arise from the summation of the individual actions of ligand-gated ion channel proteins, and decrease over time and space. They do not typically involve voltage-gated sodium and potassium channels. These impulses are incremental and may be excitatory or inhibitory. They occur at the postsynaptic dendrite as a result of presynaptic neuron firing and release of neurotransmitter, or may occur in skeletal, smooth, or cardiac muscle in response to nerve input. The magnitude of a graded potential is determined by the strength

pos: Graded potential summated IPSPs, in an area of membrane reach the cell's threshold potential. Graded potential Graded potentials are changes in membrane potential that vary in size, as opposed to being all-or-none. They arise from the summation of the individual actions of ligand-gated ion channel proteins, and decrease over time and space. They do not typically involve voltage-gated sodium and potassium channels. These impulses are incremental and may be excitatory or inhibitory. They occur at the postsynaptic dendrite as a result of presynaptic neuron firing and release of neurotransmitter, or may occur in skeletal, smooth, or cardiac muscle in response to nerve

neg: Action potential synapses, or to motor cells or glands. In other types of cells, their main function is to activate intracellular processes. In muscle cells, for example, an action potential is the first step in the chain of events leading to contraction. In beta cells of the pancreas, they provoke release of insulin. Action potentials in neurons are also known as "nerve impulses" or "spikes", and the temporal sequence of action potentials generated by a neuron is called its "spike train". A neuron that emits an action potential, or nerve impulse, is often said to "fire". Action potentials are generated by special

neg: Mechanoreceptor in the sensory neuron arising within it. This is a graded response: the greater the deformation, the greater the generator potential. If the generator potential reaches threshold, a volley of action potentials (nerve impulses) are triggered at the first node of Ranvier of the sensory neuron. Once threshold is reached, the magnitude of the stimulus is encoded in the frequency of impulses generated in the neuron. So the more massive or rapid the deformation of a single corpuscle, the higher the frequency of nerve impulses generated in its neuron. The optimal sensitivity of a lamellar corpuscle is 250 Hz, the

neg: Action potential properties of the voltage-gated ion channels that produce it. Several types of channels capable of producing the positive feedback necessary to generate an action potential do exist. Voltage-gated sodium channels are responsible for the fast action potentials involved in nerve conduction. Slower action potentials in muscle cells and some types of neurons are generated by voltage-gated calcium channels. Each of these types comes in multiple variants, with different voltage sensitivity and different temporal dynamics. The most intensively studied type of voltage-dependent ion channels comprises the sodium channels involved in fast nerve conduction. These are sometimes known as Hodgkin-Huxley sodium channels

neg: Cellular neuroscience major class of cells found in the nervous system are glial cells. These cells are only recently beginning to receive attention from neurobiologists for being involved not just in nourishment and support of neurons, but also in modulating synapses. For example, Schwann cells, which are a type of glial cell found in the peripheral nervous system, modulate synaptic connections between presynaptic terminals of motor neuron endplates and muscle fibers at neuromuscular junctions. One prominent characteristic of many neurons is excitability. Neurons generate electrical impulses or changes in voltage of two types: graded potentials and action potentials. Graded potentials occur when

neg: Stimulus (physiology) receptors and target cells through extensive, complex dendritic networks. Communication between receptors in this fashion enables discrimination and the more explicit interpretation of external stimuli. Effectively, these localized graded potentials trigger action potentials that communicate, in their frequency, along nerve axons eventually arriving in specific cortexes of the brain. In these also highly specialized parts of the brain, these signals are coordinated with others to possibly trigger a new response. If a signal from the presynaptic neuron is inhibitory, inhibitory neurotransmitters, normally GABA will be released into the synapse. This neurotransmitter causes an inhibitory postsynaptic potential in the postsynaptic neuron.

neg: Visual processing The retina is where a group of light-sensing cells, called photoreceptors are located. There are two types of photoreceptors: rods and cones. Rods are sensitive to dim light and cones are better able to transduce bright light. Photoreceptors connect to bipolar cells, which induce action potentials in retinal ganglion cells. 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

neg: Tetany fluid increase the permeability of neuronal membranes to sodium ion, causing a progressive depolarization, which increases the possibility of action potentials. This occurs because calcium ions interact with the exterior surface of sodium channels in the plasma membrane of nerve cells. When calcium ions are absent the voltage level required to open voltage gated sodium channels is significantly altered (less excitation is required). If the plasma Ca decreases to less than 50% of the normal value of 9.4 mg/dl, action potentials may be spontaneously generated, causing contraction of peripheral skeletal muscles. Hypocalcemia is not a term for tetany but is

neg: Neuron doctrine nucleus will survive. 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. The heart is an example of excitable tissue where the cells connect via cytoplasmic continuity and yet is perfectly consistent with cell theory. This is true of other examples such as connections between horizontal cells of the retina, or the Mauthner cell synapse in

neg: Sensory neuron of animal species. Sensory neuron Sensory neurons also known as afferent neurons are neurons 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. The stimulus can come from "extoreceptors" outside the body, for example light and sound, or from "interoreceptors" inside the body, for example blood pressure or the

neg: Sensory neuron Sensory neuron Sensory neurons also known as afferent neurons are neurons 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. The stimulus can come from "extoreceptors" outside the body, for example light and sound, or from "interoreceptors" inside the body, for example blood pressure or the sense of body

neg: Electrophysiology cells around it as well as which of the spikes come from which cell. This process is called spike sorting and is suitable in areas where there are identified types of cells with well defined spike characteristics. If the electrode tip is bigger still, in general the activity of individual neurons cannot be distinguished but the electrode will still be able to record a field potential generated by the activity of many cells. Extracellular field potentials are local current sinks or sources that are generated by the collective activity of many cells. Usually, a field potential is generated by the

neg: Retina bipolar cell on to the ganglion cells directly or indirectly (via amacrine cells). Unlike most neurons, bipolar cells communicate via graded potentials, rather than action potentials. Bipolar cells receive synaptic input from either rods or cones, or both rods and cones, though they are generally designated rod bipolar or cone bipolar cells. There are roughly 10 distinct forms of cone bipolar cells, however, only one rod bipolar cell, due to the rod receptor arriving later in the evolutionary history than the cone receptor. In the dark, a photoreceptor (rod/cone) cell will release glutamate, which inhibits (hyperpolarizes) the ON bipolar cells and excites

neg: Membrane potential excitation. In excitable cells, the other possible states are graded membrane potentials (of variable amplitude), and action potentials, which are large, all-or-nothing rises in membrane potential that usually follow a fixed time course. Excitable cells include neurons, muscle cells, and some secretory cells in glands. Even in other types of cells, however, the membrane voltage can undergo changes in response to environmental or intracellular stimuli. For example, depolarization of the plasma membrane appears to be an important step in programmed cell death. The interactions that generate the resting potential are modeled by the Goldman equation. This is similar in form

neg: Retina photoceptor sends a proportional response synaptically to bipolar cells which in turn signal the retinal ganglion cells. The photoreceptors are also cross-linked by horizontal cells and amacrine cells, which modify the synaptic signal before it reaches the ganglion cells, the neural signals being intermixed and combined. Of the retina's nerve cells, only the retinal ganglion cells and few amacrine cells create action potentials. In the retinal ganglion cells there are two types of response, depending on the receptive field of the cell. The receptive fields of retinal ganglion cells comprise a central, approximately circular area, where light has one effect

neg: Nerve the nerves in the cranium allowed him to differentiate between blood vessels and nerves i.e. , "“string (plant fiber), nerve”". Nerve A nerve is an enclosed, cable-like bundle of nerve fibres called axons, in the peripheral nervous system. A nerve provides a common pathway for the electrochemical nerve impulses called action potentials that are transmitted along each of the axons to peripheral organs or, in the case of sensory nerves, from the periphery back to the central nervous system. Each axon within the nerve is an extension of an individual neuron, along with other supportive cells such as Schwann cells

neg: Nerve Nerve A nerve is an enclosed, cable-like bundle of nerve fibres called axons, in the peripheral nervous system. A nerve provides a common pathway for the electrochemical nerve impulses called action potentials that are transmitted along each of the axons to peripheral organs or, in the case of sensory nerves, from the periphery back to the central nervous system. Each axon within the nerve is an extension of an individual neuron, along with other supportive cells such as Schwann cells that coat the axons in myelin. Within a nerve, each axon is surrounded by a layer of connective tissue called

neg: Hearing cochlea, and low at the apex. Basilar membrane motion causes depolarization of the hair cells, specialized auditory receptors located within the organ of Corti. While the hair cells do not produce action potentials themselves, they release neurotransmitter at synapses with the fibers of the auditory nerve, which does produce action potentials. In this way, the patterns of oscillations on the basilar membrane are converted to spatiotemporal patterns of firings which transmit information about the sound to the brainstem. The sound information from the cochlea travels via the auditory nerve to the cochlear nucleus in the brainstem. From there, the signals

neg: Electrocochleography Electrocochleography Electrocochleography (abbreviated ECochG or ECOG) is a technique of recording electrical potentials generated in the inner ear and auditory nerve in response to sound stimulation, using an electrode placed in the ear canal or tympanic membrane. The test is performed by an otologist or audiologist with specialized training, and is used for detection of elevated inner ear pressure (endolymphatic hydrops) or for the testing and monitoring of inner ear and auditory nerve function during surgery. The most common clinical applications of electrocochleography include: The basilar membrane and the hair cells of the cochlea function as a sharply tuned frequency

neg: Group C nerve fiber 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. Study of Remak bundles has important implications in nerve regeneration after sustaining injury. Currently, recovery of distal C fiber function takes months and may still only regain incomplete function.

neg: Evolution of nervous systems Evolution of nervous systems The evolution of nervous systems dates back to the first development of nervous systems in animals (or metazoans). Neurons developed as specialized electrical signaling cells in multicellular animals, adapting the mechanism of action potentials present in motile single-celled and colonial eukaryotes. Simple nerve nets seen in animals like cnidaria evolved first, followed by nerve cords in bilateral animals – ventral nerve cords in invertebrates and dorsal nerve cords supported by a notochord in chordates. Bilateralization led to the evolution of brains, a process called cephalization. Action potentials, which are necessary for neural activity, evolved in single-celled

neg: Extracellular field potential Extracellular field potential The extracellular field potential is the electrical potential produced by cells, e.g. nerve or muscle cells, outside of the cell. Electrophysiological studies investigate these potentials using extracellular microelectrodes. In these experiments the extracellular field potential will be detected as an electrical potential whose source and composition is often ambiguous, making its interpretation difficult. Individual nerve cells neurons may produce spikes seen as peaks of some tens to hundreds of microvolts. Contributions from neighboring neurons may overlap, producing extracellular potentials of up to several millivolts. Spatially integrating over even larger populations of cells, i.e. lumps of nervous or

neg: Non-spiking neuron cells, which are a type of non-spiking neurons, undergo a transformation from spiking to non-spiking cells, there have been many studies that try to identify the functional reasons for such a transformation. Starburst amacrine cells use action potentials during retinal development, and once the retina is mature, these cells transform into non-spiking neurons. The change from a cell that can generate action potentials to solely functioning off of a graded potential is drastic, and may provide insight into why the two kinds of neural networks exist. The cells lose sodium channels. The loss of the sodium channels is triggered by

neg: Molecular neuroscience cDNA library which could be used to clone the channel protein. Cloning the channel itself allowed for applications such as identifying the same channels in other animals. Sodium channels are known for working in concert with potassium channels during the development of graded potentials and action potentials. Sodium channels allow an influx of Na ions into a neuron, resulting in a depolarization from the resting membrane potential of a neuron to lead to a graded potential or action potential, depending on the degree of depolarization. Potassium channels come in a variety of forms, are present in most eukaryotic cells, and

neg: Action potential either of which may stimulate subsequent neuron(s) into firing an action potential. For illustration, in the human ear, hair cells convert the incoming sound into the opening and closing of mechanically gated ion channels, which may cause neurotransmitter molecules to be released. In similar manner, in the human retina, the initial photoreceptor cells and the next layer of cells (comprising bipolar cells and horizontal cells) do not produce action potentials; only some amacrine cells and the third layer, the ganglion cells, produce action potentials, which then travel up the optic nerve. In sensory neurons, action potentials result from an external

neg: Auditory system and forth with each cycle of sound, tilting the cilia, which is what elicits the hair cells' electrical responses. Inner hair cells, like the photoreceptor cells of the eye, show a graded response, instead of the spikes typical of other neurons. These graded potentials are not bound by the "all or none" properties of an action potential. At this point, one may ask how such a wiggle of a hair bundle triggers a difference in membrane potential. The current model is that cilia are attached to one another by "tip links", structures which link the tips of one cilium to

neg: Synaptic noise Synaptic noise Synaptic noise refers to the constant bombardment of synaptic activity in neurons. This occurs in the background of a cell when potentials are produced without the nerve stimulation of an action potential, and are due to the inherently random nature of synapses. These random potentials have similar time courses as excitatory postsynaptic potentials (EPSPs) and inhibitory postsynaptic potentials (IPSPs), yet they lead to variable neuronal responses. The variability is due to differences in the discharge times of action potentials. Many types of noise exist in cells. First, there is intrinsic noise and extrinsic, or synaptic, noise. Within each

neg: Membrane stabilizing effect Membrane stabilizing effect Membrane stabilizing effects involve the inhibition or total abolishing of action potentials from being propagated across the membrane. This phenomenon is common in nerve tissues as they are the carrier of impulses from the periphery to the central nervous system. Membrane stabilization is the method through which local anesthetics work. They block the propagation of action potentials across nerve cells, thereby producing a nerve block. Some beta-blockers also possess what is referred to as membrane stabilizing activity (MSA). This effect is similar to the membrane stabilizing activity of sodium channel blockers that represent Class I antiarrhythmics. MSA

neg: Rough-skinned newt nerve cells blocks electrical signals necessary for conducting nerve impulses. This inhibition of firing action potentials has the effect of inducing paralysis and death by asphyxiation. Throughout much of the newt’s range, the common garter snake ("Thamnophis sirtalis") has been observed to exhibit resistance to the tetrodotoxin produced in the newt's skin. While in principle the toxin binds to a tube-shaped protein that acts as a sodium channel in the snake's nerve cells, researchers have identified a genetic disposition in several snake populations where the protein is configured in such a way as to hamper or prevent binding of the

neg: Oxytocin as shown in the inset of the figure; neurophysin is a large peptide fragment of the larger precursor protein molecule from which oxytocin is derived by enzymatic cleavage. Secretion of oxytocin from the neurosecretory nerve endings is regulated by the electrical activity of the oxytocin cells in the hypothalamus. These cells generate action potentials that propagate down axons to the nerve endings in the pituitary; the endings contain large numbers of oxytocin-containing vesicles, which are released by exocytosis when the nerve terminals are depolarised. Endogenous oxytocin concentrations in the brain have been found to be as much as 1000-fold higher

neg: Electromyoneurography contractions). Various regions of muscle on the body are examined in an electromyoneurography test and the procedure lasts anywhere between 30–60 minutes (2–5 minutes per muscle). In addition to examining the muscles, the conduction velocity of nerve signals are measured. The nerve's ability to transmit signals is tested by inserting recording electrodes to capture the data, and signal electrodes to initiate signals down a nerve by applying a small shock. Self-generated potentials also occur naturally for recording, in addition to the artificial "shock". Evaluating a nerve's conduction velocity, together with testing potentials, allows for a beneficial diagnosis that can detect

neg: Tactile corpuscle vibrations, but for the same reasons, they are limited in their detection because they can only signal that something is touching the skin. Any physical deformation of the corpuscle will cause sodium ions to enter it, creating an action potential in the corpuscle's nerve fiber. Since they are rapidly adapting or phasic, the action potentials generated quickly decrease and eventually cease (this is the reason one stops "feeling" one's clothes). If the stimulus is removed, the corpuscle regains its shape and while doing so (i.e.: while physically reforming) causes another volley of action potentials to be generated. Tactile corpuscle Tactile

neg: Synapse calcium into the post-synaptic cell, which are the most analyzed forms of plasticity at excitatory synapses. For technical reasons, synaptic structure and function have been historically studied at unusually large model synapses, for example: The function of neurons depends upon cell polarity. The distinctive structure of nerve cells allows action potentials to travel directionally (from dendrites to cell body down the axon), and for these signals to then be received and carried on by post-synaptic neurons or received by effector cells. Nerve cells have long been used as models for cellular polarization, and of particular interest are the mechanisms underlying

neg: Binaural fusion of rapidly adjusting tuning properties depending on the context in which sounds are heard. Each eardrum moves one-dimensionally; the auditory brain analyzes and compares movements of both eardrums to extract physical cues and synthesize auditory objects. When stimulation from a sound reaches the ear, the eardrum deflects in a mechanical fashion, and the three middle ear bones (ossicles) transmit the mechanical signal to the cochlea, where hair cells transform the mechanical signal into an electrical signal. The auditory nerve, also called the cochlear nerve, then transmits action potentials to the central auditory nervous system. In binaural fusion, inputs from both

neg: Stimulus (physiology) these cells result from opening of non-selective cation channels upon binding of the odorant to the specific receptor. G protein-coupled receptors in the plasma membrane of these cells can initiate second messenger pathways that cause cation channels to open. In response to stimuli, the sensory receptor initiates sensory transduction by creating graded potentials or action potentials in the same cell or in an adjacent one. Sensitivity to stimuli is obtained by chemical amplification through second messenger pathways in which enzymatic cascades produce large numbers of intermediate products, increasing the effect of one receptor molecule. Though receptors and stimuli are varied,

neg: Inflammatory reflex and other cytokines which cause damaging inflammation. Signaling in the efferent arc of the inflammatory reflex, termed the "Cholinergic anti-inflammatory pathway," provides a regulatory check on the innate immune system response to invasion and injury. The action potentials arising in the vagus nerve are transmitted to the spleen, where a subset of specialized T cells is activated to secrete acetylcholine. The net effect of the reflex is to prevent the damage caused by excessive cytokine production. Evidence from experimental disease models of arthritis, colitis, sepsis, hemorrhagic shock, and congestive heart failure indicate that electrical stimulation of the vagus nerve can

neg: Muscle contraction fine control and gradual responses, much like motor unit recruitment in skeletal muscle. The contractile activity of smooth muscle cells is influenced by multiple inputs such as spontaneous electrical activity, neural and hormonal inputs, local changes in chemical composition, and stretch. This is in contrast to the contractile activity of skeletal muscle cells, which relies on a single neural input. Some types of smooth muscle cells are able to generate their own action potentials spontaneously, which usually occur following a pacemaker potential or a slow wave potential. These action potentials are generated by the influx of extracellular , and not

neg: Threshold potential are sufficient to generate an action potential. It relies on a balance of incoming inhibitory and excitatory stimuli. The potentials generated by the stimuli are additive, and they may reach threshold depending on their frequency and amplitude. Normal functioning of the central nervous system entails a summation of synaptic inputs made largely onto a neuron's dendritic tree. These local graded potentials, which are primarily associated with external stimuli, reach the axon initial segment and build until they manage to reach the threshold value. The larger the stimulus, the greater the depolarization, or attempt to reach threshold. The task of depolarization

neg: Merkel nerve ending functions as the enterochromaffin cell, the mechanosensory cell in the GI epithelium, which synthesizes 95% of the body's total serotonin or 5-HT. Like the cells responsible for the mechanotransduction in hearing, Merkel cells transduce mechanical forces into excitatory signals via ion conductance on mechanosensitive channels. of which Piezo2 is the Merkel cell´s primary mechanosensor. The Merkel cell´s somewhat rigid structure, and the fact that they are not encapsulated, causes them to have a sustained response in the form of action potentials or spikes) to mechanical deflection of the tissue. Because of their sustained response to pressure, Merkel nerve endings are

neg: Hair cell action potential. Instead, the influx of positive ions from the endolymph in the scala media depolarizes the cell, resulting in a receptor potential. This receptor potential opens voltage gated calcium channels; calcium ions then enter the cell and trigger the release of neurotransmitters at the basal end of the cell. The neurotransmitters diffuse across the narrow space between the hair cell and a nerve terminal, where they then bind to receptors and thus trigger action potentials in the nerve. In this way, the mechanical sound signal is converted into an electrical nerve signal. Repolarization of hair cells is done in

neg: Action potential the afterhyperpolarization. In animal cells, there are two primary types of action potentials. One type is generated by voltage-gated sodium channels, the other by voltage-gated calcium channels. Sodium-based action potentials usually last for under one millisecond, but calcium-based action potentials may last for 100 milliseconds or longer. In some types of neurons, slow calcium spikes provide the driving force for a long burst of rapidly emitted sodium spikes. In cardiac muscle cells, on the other hand, an initial fast sodium spike provides a "primer" to provoke the rapid onset of a calcium spike, which then produces muscle contraction. In the

neg: Cochlea Corti, and determines the mechanical wave propagation properties of the cochlear system. The cochlea is filled with a watery liquid, the perilymph, which moves in response to the vibrations coming from the middle ear via the oval window. As the fluid moves, the cochlear partition (basilar membrane and organ of Corti) moves; thousands of hair cells sense the motion via their stereocilia, and convert that motion to electrical signals that are communicated via neurotransmitters to many thousands of nerve cells. These primary auditory neurons transform the signals into electrochemical impulses known as action potentials, which travel along the auditory nerve

neg: Stimulus (physiology) most extrinsic stimuli first generate localized graded potentials in the neurons associated with the specific sensory organ or tissue. In the nervous system, internal and external stimuli can elicit two different categories of responses: an excitatory response, normally in the form of an action potential, and an inhibitory response. When a neuron is stimulated by an excitatory impulse, neuronal dendrites are bound by neurotransmitters which cause the cell to become permeable to a specific type of ion; the type of neurotransmitter determines to which ion the neurotransmitter will become permeable. In excitatory postsynaptic potentials, an excitatory response is generated. This

neg: Ventral cochlear nucleus spherical bushy cells likely project to the ipsilateral lateral superior olive. They project neither to the medial superior olives or to the medial nucleus of the trapezoid body. Multipolar cells fall into two distinct groups. Those whose axons project out of the aVCN through the trapezoid body, T stellate cells, have longer dendrites than bushy cells that characteristically lie in line with fascicles of auditory nerve fibers. These principal cells are excitatory. Another name for these cells is 'choppers'. They have an intrinsical rhythm, and will fire action potentials with this rhythm once activated by the right sound. The anteroventral

neg: Schwannomatosis Schwannomatosis Schwannomatosis is one form of a genetic disorder called neurofibromatosis (NF) that has only recently been recognized. Originally described in Japanese patients, it consists of multiple cutaneous schwannomas, central nervous system tumors, and other neurological complications, excluding hallmark signs of NF. It is a rare disorder, affecting only around 1 in 40,000 individuals. Schwannomas are mostly benign tumors that commonly occur in individuals with NF2 and schwannomatosis (sometimes called neurofibromatosis type III). Schwann cells are glial cells that myelinate the axons of nerve cells. Myelin is a lipid covering that speeds the conduction of action potentials. When Schwann cells

neg: Nervous tissue PNS are satellite cells and Schwann cells. In the central nervous system (CNS), the tissue types found are grey matter and white matter. The tissue is categorized by its neuronal and neuroglial components. Neurons are cells with specialized features that allow them to receive and facilitate nerve impulses, or action potentials, across their membrane to the next neuron. They possess a large cell body (soma), with cell projections called dendrites and an axon. Dendrites are thin, branching projections that receive electrochemical signaling (neurotransmitters) to create a change in voltage in the cell. Axons are long projections that carry the action

neg: Apical dendrite time scale. EEG scalp signals are summed EPSPs and IPSPs of nerve cells. EEG can only measure the potentials of cells arranged in organized layers and whose apical dendrites are oriented perpendicularly to the surface of the cortex (as they are in pyramidal cells). The potential measured by the EEG is the difference between the basal and apical parts of the active neurons that are oriented in such a way. The EPSPs that converge on the pyramidal neurons through direct afferent fibers ending in the upper part of the apical dendrites cause a flow of charged ions (a current) between

neg: Electrophysiological techniques for clinical diagnosis or inactive during movement (onset of activity), assessing the velocity of nerve conduction, and the amount of force generated during movement. Of these uses, determining the onset of muscle activity has been shown to be the most accurate. The firing of neurons throughout the brain has been known to have localized relationships to certain functions, processes and reactions to stimuli. With proper equipment it is possible to locate where in the brain neurons have been activated and measure their event related potentials. Event-related potentials can be classified as either: sensory, motor or cognitive. Measurement of spontaneous electrophysiological activity does not

neg: Motor neuron and along with the signals, determine whether a motor neuron will be more rostral or caudal in character. In the spinal column, Hox 4-11 sort motor neurons to one of the five motor columns. Upper motor neurons originate in the motor cortex located in the precentral gyrus. The cells that make up the primary motor cortex are Betz cells, which are a type of pyramidal cell. The axons of these cells descend from the cortex to form the corticospinal tract. Nerve tracts are bundles of axons as white matter, that carry action potentials to their effectors. In the spinal cord

neg: Neurotransmitter the dopamine system. The addictive opiate drugs exert their effects primarily as functional analogs of opioid peptides, which, in turn, regulate dopamine levels. Neurons form elaborate networks through which nerve impulses—action potentials—travel. Each neuron has as many as 15,000 connections with neighboring neurons. Neurons do not touch each other (except in the case of an electrical synapse through a gap junction); instead, neurons interact at contact points called synapses: a junction within two nerve cells, consisting of a miniature gap within which impulses are carried by a neurotransmitter. A neuron transports its information by way of a nerve impulse called

neg: Axon terminal Axon terminal Axon terminals (also called synaptic boutons or terminal boutons) are distal terminations of the telodendria (branches) of an axon. An axon, also called a nerve fiber, is a long, slender projection of a nerve cell, or neuron, that conducts electrical impulses called action potentials away from the neuron's cell body, or soma, in order to transmit those impulses to other neurons, muscle cells or glands. Neurons are interconnected in complex arrangements, and use electrochemical signals and neurotransmitter chemicals to transmit impulses from one neuron to the next; axon terminals are separated from neighboring neurons by a small gap

neg: Computational auditory scene analysis occurring around 4 kHz. As the organ of hearing, the cochlea consists of two membranes, Reissner’s and the basilar membrane. The basilar membrane moves to audio stimuli through the specific stimulus frequency matches the resonant frequency of a particular region of the basilar membrane. The movement the basilar membrane displaces the inner hair cells in one direction, which encodes a half-wave rectified signal of action potentials in the spiral ganglion cells. The axons of these cells make up the auditory nerve, encoding the rectified stimulus. The auditory nerve responses select certain frequencies, similar to the basilar membrane. For lower frequencies,

neg: Transduction (physiology) middle ear (the ossicles) to vibrate. These vibrations then pass into the cochlea, the organ of hearing. Within the cochlea, the hair cells on the sensory epithelium of the organ of Corti bend and cause movement of the basilar membrane. The membrane undulates in different sized waves according to the frequency of the sound. Hair cells are then able to convert this movement (mechanical energy) into electrical signals (graded receptor potentials) which travel along auditory nerves to hearing centres in the brain. In the olfactory system, odorant molecules in the mucus bind to G-protein receptors on olfactory cells. The G-protein

neg: Functional electrical stimulation to re-learn how to execute impaired functions, instead of making the consumer dependent on neuroprostheses for the rest of her/his life. Neurons are electrically active cells. In neurons, information is coded and transmitted as a series of electrical impulses called action potentials, which represent a brief change in cell electric potential of approximately 80–90 mV. Nerve signals are frequency modulated; i.e. the number of action potentials that occur in a unit of time is proportional to the intensity of the transmitted signal. Typical action potential frequency is between 4 and 12 Hz. An electrical stimulation can artificially elicit this action

neg: Axon is provided by another type of glial cell, the oligodendrocyte. Schwann cells myelinate a single axon. An oligodendrocyte can myelinate up to 50 axons. Nodes of Ranvier (also known as "myelin sheath gaps") are short unmyelinated segments of a myelinated axon, which are found periodically interspersed between segments of the myelin sheath. Therefore, at the point of the node of Ranvier, the axon is reduced in diameter. These nodes are areas where action potentials can be generated. In saltatory conduction, electrical currents produced at each node of Ranvier are conducted with little attenuation to the next node in line, where

neg: Development of the nervous system posteriorly in the spinal cord. Hoxb-1 is expressed in rhombomere 4 and gives rise to the facial nerve. Without this Hoxb-1 expression, a nerve similar to the trigeminal nerve arises. Neurogenesis is the process by which neurons are generated from neural stem cells and progenitor cells. Neurons are 'post-mitotic', meaning that they will never divide again for the lifetime of the organism. Neuronal migration is the method by which neurons travel from their origin or birthplace to their final position in the brain. There are several ways they can do this, e.g. by radial migration or tangential migration. This time

neg: Cardiac pacemaker controls the rate of contraction for the entire heart muscle because its cells have the quickest rate of spontaneous depolarization, thus they initiate action potentials the quickest. The action potential generated by the SA node passes down the electrical conduction system of the heart, and depolarizes the other potential pacemaker cells (AV node) to initiate action potentials before these other cells have had a chance to generate their own spontaneous action potential, thus they contract and propagate electrical impulses to the pace set by the cells of the SA node. This is the normal conduction of electrical activity in the

neg: Neural tissue engineering Methods of eliminating the immunogenic cells, thus leaving behind only the ECM-components of the tissue, are currently being investigated to increase the efficacy of nonautologous tissue grafts. Guidance methods of PNS regeneration use nerve guide channels to help axons regrow along the correct path, and may direct growth factors secreted by both ends of the nerve to promote growth and reconnection. Guidance methods reduce scarring of the nerves, increasing the functionality of the nerves to transmit action potentials after reconnection. Two types of materials are used in guidance methods of PNS regeneration: natural-based materials and synthetic materials. Natural-based materials are

neg: Evoked potential which indicates the average peak latency for that particular wave. For example, P100 is a wave with a positive peak at approximately 100 ms following stimulus onset. The average amplitude for VEP waves usually falls between 5 and 20 microvolts. Normal values are depending on used stimulation hardware (flash stimulus vs. cathode ray tube or liquid crystal display, checkerboard field size, etc.). Some specific VEPs are: Auditory evoked potentials (AEP) can be used to trace the signal generated by a sound through the ascending auditory pathway. The evoked potential is generated in the cochlea, goes through the cochlear nerve, through

neg: Tickling studied the knismesis type of tickle in cats, by measuring the action potentials generated in the nerve fibres while lightly stroking the skin with a piece of cotton wool. Zotterman found that the "tickling" sensation depended, in part, on the nerves that generate pain. Further studies have discovered that when the pain nerves are severed by surgeons, in an effort to reduce intractable pain, the tickle response is also diminished. However, in some patients that have lost pain sensation due to spinal cord injury, some aspects of the tickle response do remain. Tickle may also depend on nerve fibres associated

neg: Neuroeffector junction de novo as calcium concentration increases in nerve terminals upon membrane depolarization. Enteric nerve terminals make intimate synapses with ICC-IM, which are situated between the nerve terminals and neighbouring smooth muscle cells. ICC-IM play a critical role in the reception and transduction of cholinergic excitatory and nitrergic inhibitory neurotransmission. ICC-IM form gap junctions with smooth muscle cells and post-junctional electrical responses generated in ICC are conducted to the smooth muscle syncytium. By this contact, ICC can regulate the neuromuscular responses observed throughout the GI tract. Recent morphological evidence using anterograde tracing methods, has shown close apposition between vagal and spinal

neg: Renshaw cell "et al.", provided evidence that these interneurons, which they called “Renshaw Cells,” are stimulated by acetylcholine from motor neurons. Previous work by Renshaw and Lloyd had shown that this antidromic inhibition resembled direct inhibition from spinal nerves but resulted in relatively longer inhibition of 40-50 ms (compared to 15 ms). The antidromic stimulation of the nerve fiber also resulted in action potentials in the cell bodies of the motor neurons along with hyperpolarization of other groups of motor neurons. In the event where the initial stimulation of the motor neuron originated in a spinal tract the Renshaw cell spike occurred

neg: Psychoacoustics sensory and perceptual event; in other words, when a person hears something, that something arrives at the ear as a mechanical sound wave traveling through the air, but within the ear it is transformed into neural action potentials. The outer hair cells (OHC) of a mammalian cochlea give rise to an enhanced sensitivity and better frequency resolution of the mechanical response of the cochlear partition. These nerve pulses then travel to the brain where they are perceived. Hence, in many problems in acoustics, such as for audio processing, it is advantageous to take into account not just the mechanics of

neg: Graded potential released. The transmitter diffuses across the synaptic cleft and activates ligand-gated ion channels that mediate the EPSP. The amplitude of the EPSP is directly proportional to the number of synaptic vesicles that were released. If the EPSP is not large enough to trigger an action potential, the membrane subsequently repolarizes to its resting membrane potential. This shows the temporary and reversible nature of graded potentials. Graded potentials that make the membrane potential more negative, and make the postsynaptic cell less likely to have an action potential, are called inhibitory post synaptic potentials (IPSPs). Hyperpolarization of membranes is caused by influx

neg: Human brain of liquids within the inner ear is generated by motion (for balance) and transmitted vibrations generated by the ossicles (for sound). This creates a nerve signal that passes through the vestibulocochlear nerve. From here, it passes through to the cochlear nuclei, the superior olivary nucleus, the medial geniculate nucleus, and finally the auditory radiation to the auditory cortex. The sense of smell is generated by receptor cells in the epithelium of the olfactory mucosa in the nasal cavity. This information passes through a relatively permeable part of the skull to the olfactory nerve. This nerve transmits to the neural circuitry

neg: Local field potential Local field potential A local field potential (LFP) is an electrophysiological signal generated by the summed electric current flowing from multiple nearby neurons within a small volume of nervous tissue. Voltage is produced across the local extracellular space by action potentials and graded potentials in neurons in the area, and varies as a result of synaptic activity. "Potential" refers to electrical potential, or voltage, and particularly to voltage that is typically recorded with a microelectrode embedded within neuronal tissue, in the brain of an anesthetized animal, within a thin slice of brain tissue maintained "in vitro," or within humans for

neg: Electricity electric fields, an ability known as electroreception, while others, termed electrogenic, are able to generate voltages themselves to serve as a predatory or defensive weapon. The order Gymnotiformes, of which the best known example is the electric eel, detect or stun their prey via high voltages generated from modified muscle cells called electrocytes. All animals transmit information along their cell membranes with voltage pulses called action potentials, whose functions include communication by the nervous system between neurons and muscles. An electric shock stimulates this system, and causes muscles to contract. Action potentials are also responsible for coordinating activities in certain

neg: Graded potential of the stimulus. Graded potentials that make the membrane potential less negative or more positive, thus making the postsynaptic cell more likely to have an action potential, are called excitatory postsynaptic potentials (EPSPs). Depolarizing local potentials sum together, and if the voltage reaches the threshold potential, an action potential occurs in that cell. EPSPs are caused by the influx of Na or Ca from the extracellular space into the neuron or muscle cell. When the presynaptic neuron has an action potential, Ca enters the axon terminal via voltage-dependent calcium channels and causes exocytosis of synaptic vesicles, causing neurotransmitter to be

neg: Action potential by having a very high concentration of voltage-activated sodium channels. In general, it is considered to be the spike initiation zone for action potentials, i.e. the trigger zone. Multiple signals generated at the spines, and transmitted by the soma all converge here. Immediately after the axon hillock is the axon. This is a thin tubular protrusion traveling away from the soma. The axon is insulated by a myelin sheath. Myelin is composed of either Schwann cells (in the peripheral nervous system) or oligodendrocytes (in the central nervous system), both of which are types of glial cells. Although glial cells are

neg: Graeme Clark (doctor) that hearing, particularly for speech, might be reproduced in people with deafness if the damaged or underdeveloped ear were bypassed, and the auditory nerve electrically stimulated to reproduce the coding of sound. His initial doctoral research at the University of Sydney investigated the effect of the rate of electrical simulation on single cells and groups of cells in the auditory brainstem response, the centre where frequency discrimination is first decoded. Clark's research demonstrated that an electrode bundle with 'graded stiffness' would pass without injury around the tightening spiral of the cochlea to the speech frequency region. Until this time he

neg: Induced stem cells potentials for regenerative medicine. Unfortunately, the cells generated by this technology, potentially are not completely protected from the immune system of the patient (donor of nuclei), because they have the same mitochondrial DNA, as a donor of oocytes, instead of the patients mitochondrial DNA. This reduces their value as a source for autologous stem cell transplantation therapy, as for the present, it is not clear whether it can induce an immune response of the patient upon treatment. Induced androgenetic haploid embryonic stem cells can be used instead of sperm for cloning. These cells, synchronized in M phase and injected into

neg: Retina to various visual centres of the brain through the fibres of the optic nerve. Neural signals from the rods and cones undergo processing by other neurons, whose output takes the form of action potentials in retinal ganglion cells whose axons form the optic nerve. Several important features of visual perception can be traced to the retinal encoding and processing of light. In vertebrate embryonic development, the retina and the optic nerve originate as outgrowths of the developing brain, specifically the embryonic diencephalon; thus, the retina is considered part of the central nervous system (CNS) and is actually brain tissue. It

neg: Extracellular field potential muscular tissue, will produce signals commonly called local field potentials (LFP) that can be recorded either in the tissue or with suitable equipment at the body surface as, e.g., electroencephalogram (EEG), electrocardiogram (ECG), or electromyogram (EMG). For individual cells, the time course of the extracellular potential theoretically is inversely proportional to the transmembrane current. In practice, however, this is complicated considerably by the very complex morphology of neurons and the overlap of contributions from adjacent cells. Extracellular field potential The extracellular field potential is the electrical potential produced by cells, e.g. nerve or muscle cells, outside of the cell. Electrophysiological

neg: Nerve guidance conduit they retained the ability to differentiate into the three neural tissue lineages. It was also demonstrated that not only active synaptic vesicle recycling occurred, but also that excitatory and inhibitory connections capable of generating action potentials spontaneously were formed. Thus, neural progenitor cells are a viable and relatively unlimited source for creating functional neurons. Neural stem cells (NSCs) have the capability to self-renew and to differentiate into neuronal and glial lineages. Many culture methods have been developed for directing NSC differentiation; however, the creation of biomaterials for directing NSC differentiation is seen as a more clinically relevant and usable technology.

neg: Frank Werblin salamander retina allowed light evoked excitatory post-synaptic currents (EPSCs) to be measured for the first time, as well as their light elicited spiking potentials, and voltage-gated currents. The new slice technique allowed, for the first time, a neuron to be characterized by its natural stimulus (light), and then to be fully characterized by its morphological, histological, electrophysiological (EPSCs, voltage gated currents, and graded and spike potentials), and chemical identity. The new light-responsive slice methodology also allowed interplexiform cells to be identified and characterized for the first time, as well as sustained and transient amacrine neurons. Precise localization of synaptic inputs

neg: Postsynaptic potential Postsynaptic potential Postsynaptic potentials are changes in the membrane potential of the postsynaptic terminal of a chemical synapse. Postsynaptic potentials are graded potentials, and should not be confused with action potentials although their function is to initiate or inhibit action potentials. They are caused by the presynaptic neuron releasing neurotransmitters from the terminal bouton at the end of an axon into the synaptic cleft. The neurotransmitters bind to receptors on the postsynaptic terminal, which may be a neuron or a muscle cell in the case of a neuromuscular junction. These are collectively referred to as postsynaptic receptors, since they are

neg: Guillain–Barré syndrome syndrome is caused by an immune attack on the nerve cells of the peripheral nervous system and their support structures. The nerve cells have their body (the soma) in the spinal cord and a long projection (the axon) that carries electrical nerve impulses to the neuromuscular junction where the impulse is transferred to the muscle. Axons are wrapped in a sheath of Schwann cells that contain myelin. Between Schwann cells are gaps (nodes of Ranvier) where the axon is exposed. Different types of Guillain–Barré syndrome feature different types of immune attack. The demyelinating variant (AIDP, see below) features damage to

neg: Neural backpropagation enough from accumulating graded potentials and firing an axonal action potential will these channels be activated to propagate a signal traveling backwards (Rapp et al. 1996). Generally, EPSPs from synaptic activation are not large enough to activate the dendritic voltage-gated calcium channels (usually on the order of a couple milliamperes each) so backpropagation is typically believed to happen only when the cell is activated to fire an action potential. These sodium channels on the dendrites are abundant in certain types of neurons, especially mitral and pyramidal cells, and quickly inactivate. Initially, it was thought that an action potential could only

neg: Nerve compression syndrome an immediate effect on the ability of the nerve axons to transmit action potentials. As the compression becomes more severe over time, focal demyelination occurs, followed by axonal damage and finally scarring. The symptoms and signs depend on which nerve is affected, where along its length the nerve is affected, and how severely the nerve is affected. Positive sensory symptoms are usually the earliest to occur, particularly tingling and neuropathic pain, followed or accompanied by reduced sensation or complete numbness. Muscle weakness is usually noticed later, and is often associated with muscle atrophy. A compression neuropathy can usually be diagnosed

neg: Spike potential milliseconds. 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. In the resting state, the interior of the nerve fiber is negative to the exterior by approximately 70 to 90 millivolts. Spike potential Spike potentials are one of the action potentials, which occur in electrical activity of smooth muscle contraction in animals. These are true action potentials. 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

neg: Non-spiking neuron messages without eliciting an action potential. This is most likely due to the chemical composition of the membranes of the non-spiking neurons. They lack protein channels for sodium and are more sensitive to certain neurotransmitters. They function by propagating graded potentials and serve to modulate some neuromuscular junctions. Spiking neurons are noted as traditional action potential generating neurons. "Interneurons" is a name used to indicate neurons that are neither sensory neurons nor motory in nature, but function as an intermediary processing and transmission state for signals that have been received via dorsal root ganglia cells. A large amount of these

neg: Lateral grey column cells, that relay electrical signals through the brain and body. A nerve cell receives signals from other nerve cells through tree-branch-like extensions called dendrites and passes signals on through a long extension called an axon (or nerve fiber). Synapses are places where one cell's axon passes information to another cell's dendrite by sending chemicals called neurotransmitters across a small gap called a synaptic cleft. Synapses occur in various locations, including ganglia (singular: ganglion), which are masses of nerve cell bodies. Preganglionic nerve cells in the sympathetic nervous system (all of which come from the lateral grey column), use the neurotransmitter

neg: Bioelectromagnetics produce electrical fields and the response of cells to electromagnetic fields. Short-lived electrical events called action potentials occur in several types of animal cells which are called excitable cells, a category of cell include neurons, muscle cells, and endocrine cells, as well as in some plant cells. These action potentials are used to facilitate inter-cellular communication and activate intracellular processes. The physiological phenomena of action potentials are possible because voltage-gated ion channels allow the resting potential caused by electrochemical gradient on either side of a cell membrane to resolve. Bioelectromagnetism is studied primarily through the techniques of electrophysiology. In the

neg: Günther Johannes Paetsch nerve potentials and intercellular potentials of cardiac cells for physiological research, pacemakers for heart stimulators, cardiac defibrillators and micro electrode pullers for making both glass micro-electrodes with points from 1 to 3 microns and micro-glass tips for embryo-logical research. Paetsch had seven children in eleven years (1960-1971). His first child, Phebe Verena Paetsch, was born in 1960 in Denver, Colorado. Michaela Modjeska Paetsch was born in 1961 in Colorado Springs, as were Brigitte McClure Paetsch in 1963, Johann Sebastian Paetsch in 1964, Christian Friedeman Paetsch in 1966, Engelbert Raphael Paetsch in 1968, and Siegmund Amedeus Paetsch in 1971. Not only

neg: Dendrite Dendrite Dendrites (from Greek δένδρον "déndron", "tree"), also dendrons, are branched protoplasmic extensions of a nerve cell that propagate the electrochemical stimulation received from other neural cells to the cell body, or soma, of the neuron from which the dendrites project. Electrical stimulation is transmitted onto dendrites by upstream neurons (usually their axons) via synapses which are located at various points throughout the dendritic tree. Dendrites play a critical role in integrating these synaptic inputs and in determining the extent to which action potentials are produced by the neuron. Dendritic arborization, also known as dendritic branching, is a multi-step biological

neg: Lambert–Eaton myasthenic syndrome to sufficient delivery of calcium, and an increase in muscle contraction to normal levels, which can be demonstrated using an electrodiagnostic medicine study called needle electromyography by increasing amplitude of repeated compound muscle action potentials. The antibodies found in LEMS associated with lung cancer also bind to calcium channels in the cancer cells, and it is presumed that the antibodies originally develop as a reaction to these cells. It has been suggested that the immune reaction to the cancer cells suppresses their growth and improves the prognosis from the cancer. The diagnosis is usually made with nerve conduction study (NCS)

neg: Resting potential Theory" that explained the resting potential of nerve and muscle as a diffusion potential. Resting potential The relatively static membrane potential of quiescent cells is called the resting membrane potential (or resting voltage), as opposed to the specific dynamic electrochemical phenomena called action potential and graded membrane potential. Apart from the latter two, which occur in excitable cells (neurons, muscles, and some secretory cells in glands), membrane voltage in the majority of non-excitable cells can also undergo changes in response to environmental or intracellular stimuli . In principle, there is no difference between resting membrane potential and dynamic voltage changes

neg: Neuroscience of music brain and use of such techniques as functional magnetic resonance imaging (fMRI), transcranial magnetic stimulation (TMS), magnetoencephalography (MEG), electroencephalography (EEG), and positron emission tomography (PET). Children who study music have shown increased development in the auditory pathway after only two years. The development could accelerate language and reading development. Successive parts of the tonotopically organized basilar membrane in the cochlea resonate to corresponding frequency bandwidths of incoming sound. The hair cells in the cochlea release neurotransmitter as a result, causing action potentials down the auditory nerve. The auditory nerve then leads to several layers of synapses at numerous nuclei in

neg: Optic neuropathy permanent and progressive. 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. Optic neuropathy Optic neuropathy is damage to the optic nerve from any cause. Damage and death of these nerve cells, or neurons, leads to characteristic features of optic neuropathy. The main symptom is loss of vision, with colors appearing subtly washed out in the

neg: Sucrose gap Sucrose gap 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. The sucrose gap technique was first introduced by

neg: Olivocochlear system placed on the nerve bundle. These studies have measured the output of the auditory nerve (AN), with and without OCB stimulation. In 1956, Galambos activated the efferent fibres of the cat by delivering shock stimuli to the floor of the fourth ventricle (at the decussation of the COCB). Galambos observed a suppression of the compound action potentials of the AN (referred to as the N1 potential) evoked by low-intensity click stimuli. This basic finding was repeatedly confirmed (Desmedt and Monaco, 1961; Fex, 1962; Desmedt, 1962; Wiederhold, 1970). An efferent suppression of N1 was also observed by stimulating the MOCS cells

neg: Postsynaptic potential potential will change by the difference between them. Temporal summation: When a cell receives inputs that are close together in time, they are also added together, even if from the same synapse. Thus, if a neuron receives an excitatory postsynaptic potential, and then the presynaptic neuron fires again, creating another EPSP, then the membrane of the postsynaptic cell is depolarized by the total of the EPSPs. Postsynaptic potential Postsynaptic potentials are changes in the membrane potential of the postsynaptic terminal of a chemical synapse. Postsynaptic potentials are graded potentials, and should not be confused with action potentials although their function

neg: P-type calcium channel 1989 because they were discovered within mammalian Purkinje neurons. They were able to use an "in vitro" preparation to examine the ionic currents that account for Purkinje cells' electrophysiological properties. They found that there are calcium dependent action potentials which rise slowly and fall quickly then undergo hyperpolarization. The action potentials were voltage dependent and the afterhyperpolarizing potentials were connected to the spike bursts, located within the dendrites of the Purkinje cells. Without calcium flux in the Purkinje cells, action potentials fire sporadically at a high frequency. P-type calcium channels are voltage dependent calcium channels that are classified under the

neg: Evoked potential and other biological signals and ambient noise, signal averaging is usually required. The signal is time-locked to the stimulus and most of the noise occurs randomly, allowing the noise to be averaged out with averaging of repeated responses. Signals can be recorded from cerebral cortex, brain stem, spinal cord and peripheral nerves. Usually the term "evoked potential" is reserved for responses involving either recording from, or stimulation of, central nervous system structures. Thus evoked compound motor action potentials (CMAP) or sensory nerve action potentials (SNAP) as used in nerve conduction studies (NCS) are generally not thought of as evoked potentials,

neg: Pain and pleasure and articular capsules, muscles, tendons, periosteum, and arterial vessels. Once stimuli are received, the various afferent action potentials are triggered and pass along various fibers and axons of these nociceptive nerve cells into the dorsal horn of the spinal cord through the dorsal roots. A neuroanatomical review of the pain pathway, "Afferent pain pathways" by Almeida, describes various specific nociceptive pathways of the spinal cord: spinothalamic tract, spinoreticular tract, spinomesencephalic tract, spinoparabrachial tract, spinohypothalamic tract, spinocervical tract, postsynaptic pathway of the spinal column. Activity in many parts of the brain is associated with pain perception. Some of the known parts

neg: Congenital insensitivity to pain channels are expressed at high levels in nociceptive neurons of the dorsal root ganglia. As these channels are likely involved in the formation and propagation of action potentials in such neurons, it is expected that a loss of function mutation in SCN9A leads to abolished nociceptive pain propagation. PRDM12 gene is normally switched on during the development of pain-sensing nerve cells. People with homozygous mutations of the PRDM12 gene experience congenital insensitivity to pain (CIP). Developmental disabilities such as autism can include varying degrees of pain insensitivity as a sign. However, since these disorders are characterized by dysfunction of the

neg: Retinal waves connections between cells and maturation of processes in the retina. Waves are generated at random, but limited spatially due to a refractory period in cells after bursts of action potentials have been produced. After a wave has been propagated in one place, it cannot be propagated in the same place. Wave induced refractory areas last about forty to sixty seconds. Research suggests that every region of the retina is at equal probability of generating and propagating a wave. The refractory period also determines the velocity (distance between wave fronts per unit time) and periodicity (average time interval between wave-induced calcium

neg: Electroneuronography factors: Bell’s palsy, injury resulting from surgical error, trauma to the temporal bone, otitis media, multiple sclerosis, mumps, chicken pox, and other conditions. Electroneuronography tests are performed by audiologists, and have been since their invention in the late 1970s, when they replaced acoustic reflex measurements. Typically, the system calculates the difference between compound muscle action potentials generated near the nose (nasolabial fold) in response to supramaximal electrical stimulation near the ear (stylomastoid foramen). Thus, the electrical stimulus travels along the facial nerve, allowing it to be specifically pinpointed. Increasing sensitivity and specificity of the recordings has been a constant goal,

neg: Membrane potential +100 mV is the full operating range of membrane potential, the effect is that Na channels always pull the membrane potential up, K channels pull it down, and Cl channels pull it toward the resting potential. Graded membrane potentials are particularly important in neurons, where they are produced by synapses—a temporary change in membrane potential produced by activation of a synapse by a single graded or action potential is called a postsynaptic potential. Neurotransmitters that act to open Na channels typically cause the membrane potential to become more positive, while neurotransmitters that act on K channels typically cause it to