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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 ...
Additionally, BP control in those with diabetes is helpful, while intravenous immunoglobulin is used for multifocal motor neuropathy. [ 1 ] According to Lopate, et al., methylprednisolone is a viable treatment for chronic inflammatory demyelinative polyneuropathy (which can also be treated with intravenous immunoglobulin).
Since an axon can be unmyelinated or myelinated, the action potential has two methods to travel down the axon. These methods are referred to as continuous conduction for unmyelinated axons, and saltatory conduction for myelinated axons. Saltatory conduction is defined as an action potential moving in discrete jumps down a myelinated axon.
Nerve impulses are extremely slow compared to the speed of electricity, where the electric field can propagate with a speed on the order of 50–99% of the speed of light; however, it is very fast compared to the speed of blood flow, with some myelinated neurons conducting at speeds up to 120 m/s (432 km/h or 275 mph) [citation needed].
The unmyelinated parts of the nerve fiber are nodes of Ranvier. This way of action potential propagation is called saltatory conduction (red arrows in the diagram) Ion channels open, allow sodium ions to enter the cell leading to membrane depolarization and generation of action potential.
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]
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 ...
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.