Figure 14-11.

Central Nervous System (CNS) Myelin.

Oligodendroglia myelinate axons within the CNS (also see Fig. 14-3). A, As depicted in this illustration, each oligodendrocyte sends out numerous cytoplasmic processes that repetitively encircle (myelinate) the portion of an axon between two nodes of Ranvier (internode) on the same and several different axons. Direct or indirect injury to an oligodendrocyte can result in “demyelination” of those internodes myelinated by that oligodendrocyte. This injury will slow the rate of conduction of an action potential and depending on the site of the lesion, may lead to clinical signs of neural dysfunction (ataxia, proprioception deficits). B, CNS nerves, longitudinal section. Axons and their neurofilaments (brown stain) and myelin (red stain) are demonstrated by this immunohistochemical stain for neurofilament and myelin basic protein.

(Courtesy Dr. J.F. Zachary, College of Veterinary Medicine, University of Illinois.)