What is myelin?

Myelin is a white, fatty substance that forms an insulating wrapping around large nerve axons. In the peripheral nervous system, myelin is formed by Schwann cells (a type of supporting cell) that wrap repeatedly around the axon. In the central nervous system, myelin is formed by repeated wrappings of processes of oligodendrocytes (a different type of supporting cell). The process of each cell forms part of the myelin sheath. The space between the myelin from individual Schwann cells or oligodendrocyte processes is a bare region of the axon called the node of Ranvier. Nerve conduction is faster in myelinated fibers because it jumps from one node of Ranvier to the next. For this reason, it is called saltatory (jumping) conduction.