The Myelin Sheath
The myelin sheath protects the axon (the part of the nerve cell that transmits signals to other nerve cells.) from electrical activity. The insulation it provides increases the rate of transmission of signals. The myelin sheath is fat meaning that it is a good insulator. A gap between each myelin sheath cell occurs along the axon. In multiple sclerosis, the myelin sheath is damaged or lost causing disruption in muscle control, vision and speech.
Myelin cells are a type of glial cells. The function of a glial cell is to support neurons. The two types of glial cells that make up the myelin sheath are oligodendrocytes in the central nervous system and Schwann cells in the peripheral nervous system.