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Remyelination is the process of propagating oligodendrocyte precursor cells to form oligodendrocytes to create new myelin sheaths on demyelinated axons in the Central nervous system (CNS). This is a process naturally regulated in the body and tends to be very efficient in a healthy CNS. [ 1 ]
A single oligodendrocyte can extend its processes to cover up to 40 axons, that can include multiple adjacent axons. [2] The myelin sheath is not continuous but is segmented along the axon's length at gaps known as the nodes of Ranvier. In the peripheral nervous system the myelination of axons is carried out by Schwann cells. [1]
Myelin (/ ˈ m aɪ. ə l ɪ n / MY-ə-lin) is a lipid-rich material that surrounds nerve cell axons to insulate them and increase the rate at which electrical impulses (called action potentials) pass along the axon. [1] [2] The myelinated axon can be likened to an electrical wire (the axon) with insulating material (myelin) around it. However ...
These axons form the optic nerve, optic chiasm, and optic tract. A small percentage of retinal ganglion cells contribute little or nothing to vision, but are themselves photosensitive; their axons form the retinohypothalamic tract and contribute to circadian rhythms and pupillary light reflex, the resizing of the pupil.
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 .
The implementation of this method of study has long allowed for experimental observation of myelinogenesis in a model organism nerve that consists entirely of unmyelinated axons. Furthermore, the use of the rat optic nerve helped provide insight for early myelinogenesis researchers into improper and atypical courses of myelinogenesis.
The amacrine cells also introduce lateral inhibition to the axon terminal, serving various visual functions including efficient signal transduction with high signal-to-noise ratio. [ 3 ] The mechanism for producing the center of a bipolar cell's receptive field is well known: direct innervation of the photoreceptor cell above it, either through ...
In chronic MS lesions where remyelination is incomplete, there is evidence that there are oligodendrocytes with processes extending toward demyelinated axons, but they do not seem to be able to generate new myelin. [63] The mechanisms that regulate differentiation of OPCs into myelinating oligodendrocytes are an active area of research.