Two types of cells produce the myelin sheath . A Schwann cell wraps around only a single axon. The single versus multiple axon difference is important to the way that neurons might or might not be able to regenerate following damage. It takes many cells to produce myelin throughout the length of the axon. There are distinct gaps, called nodes of Ranvier , between the segments of myelin produced by these cells.
Myelin is critical in accelerating the speed with which information can be transmitted down an axon.
Multiple sclerosis , a crippling disease often appearing in early adulthood, attacks and destroys the myelin sheath which results in a deterioration and confusion of signals in the nervous system. Eventually, deprived of their myelin and the ability to function properly, the neurons die. There a numerous types of neurons to be found in the nervous system. Each type is somewhat different in its specialization. Pseudo-unipolar neurons connect peripheral receptors to the spinal cord.