Demyelinating Diseases - II
Myelin is an important component of the nervous system. It is a fatty substance made up of lipids and proteins and its high concentration in the white matter of the brain is responsible for that region’s characteristic whitish color. Myelin is the main component of the sheaths that envelop axons in their trajectory from the neuronal cell body to the synapses. The functions of myelin are: (a) preventing short-circuiting (and thus cross-talk) between axons by providing an insulating layer of high electrical resistance between neighboring axons, and (b) increasing the speed of signal conduction along axons. Myelin is produced in the central nervous system by oligodendrocytes and in the peripheral nervous system by Schwann cells. The myelin sheaths enveloping axons are flat extensions of oligodendrocytes or Schwann cells that spiral around an axon to form concentric lamellae. Along the course of an individual axon multiple lamellae are found. These are separated from each other by short, unmyelinated stretches known as the nodes of Ranvier. Action potentials are propagated along axons by jumping from one node of Ranvier to the next.
KeywordsWhite Matter Progressive Multifocal Leukoencephalopathy Cerebral Amyloid Angiopathy Demyelinating Disease Progressive Multifocal Leukoencephalopathy
Unable to display preview. Download preview PDF.