Intro | Schwann Cell | Astrocyte | Oligodendrocyte | Microglia
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The Schwann Cell provides a supportive role in the peripheral nervous system and is, therefore, a satellite cell. Schwann cells wrap individually around the shaft of peripheral axons, forming a layer or myelin sheath along segments of the axon. Schwann cells are composed primarily of lipids or fats; the fat serves as an insulator thereby speeding the transmission rate of action potentials along the axon. The electrical impulse effectively jumps from one segment of exposed axon membrane to the next. The exposed cell membrane between each Schwann cell is called a node of Ranvier, and the accelerated form of transmission made possible by these cells is called saltatory conduction (after saltare, the Latin word meaning to jump).
Schwann cells are also essential to the process of neuronal regeneration in the peripheral nervous system. When an axon is dying, the Schwann cells surrounding it aid in its digestion. This leaves an empty channel formed by successive Schwann cells, through which a new axon may grow from a severed end at a rate of 3-4 millimeters a day.