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In this respect, auditory nerve fibers are somewhat unusual in that action potentials pass through the soma. Both the peripheral process and the axon are myelinated . In humans, there are on average 30,000 nerve fibers within the cochlear nerve. [ 2 ]
The main purpose of myelin is to increase the speed at which electrical impulses (known as action potentials) propagate along the myelinated fiber. In unmyelinated fibers, action potentials travel as continuous waves, but, in myelinated fibers, they "hop" or propagate by saltatory conduction. The latter is markedly faster than the former, at ...
Image description: Schematic representation of the action potential propagation through myelinated nerve fiber of peripheral nervous system. From axon hillock of neuron body (soma) action potential propagates from one unmyelinated fiber part to the next one. The unmyelinated parts of the nerve fiber are nodes of Ranvier.
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. [1] [2]
An action potential occurs when the membrane potential of a specific cell rapidly rises and falls. [1] This depolarization then causes adjacent locations to similarly depolarize. Action potentials occur in several types of excitable cells, which include animal cells like neurons and muscle cells, as well as some plant cells.
An action potential is a spike of both positive and negative ionic discharge that travels along the membrane of a cell. [15] The creation and conduction of action potentials represents a fundamental means of communication in the nervous system. Action potentials represent rapid reversals in voltage across the plasma membrane of axons.
Aδ fibers are characterized by thin axons and thin myelin sheaths, and are either D-hair receptors or nociceptive neurons. Aδ fibers conduct at a rate of up to 25 m/s. D-hair receptors have large receptive fields and very low mechanical thresholds, and have been shown to be the most sensitive of known cutaneous mechanoreceptors.
Fig. 1. Neuron and myelinated axon, with signal flow from inputs at dendrites to outputs at axon terminals. The signal is a short electrical pulse called action potential or 'spike'. Fig 2. Time course of neuronal action potential ("spike"). Note that the amplitude and the exact shape of the action potential can vary according to the exact ...