Which cells form the myelin sheath in the PNS?

Which cells form the myelin sheath in the PNS?

• A. Oligodendrocytes
• B. Schwann cells
• C. Microglia
• D. Astrocytes

Answer: (B)

Myelin in the peripheral nervous system is formed by Schwann cells. These glial cells wrap their membrane around segments of a single axon, creating multiple tightly layered layers that insulate the fiber and greatly speed up nerve impulse conduction through saltatory conduction. The gaps between wrapped segments are the nodes of Ranvier, which boost transmission speed. In contrast, in the central nervous system this myelin is produced by oligodendrocytes, each of which can extend several processes to myelinate multiple nearby axons. Microglia are immune cells involved in debris cleanup and inflammatory responses, not myelination, and astrocytes support neurons and the extracellular environment without forming myelin in the PNS.

Myelin in the peripheral nervous system is formed by Schwann cells. These glial cells wrap their membrane around segments of a single axon, creating multiple tightly layered layers that insulate the fiber and greatly speed up nerve impulse conduction through saltatory conduction. The gaps between wrapped segments are the nodes of Ranvier, which boost transmission speed.

In contrast, in the central nervous system this myelin is produced by oligodendrocytes, each of which can extend several processes to myelinate multiple nearby axons. Microglia are immune cells involved in debris cleanup and inflammatory responses, not myelination, and astrocytes support neurons and the extracellular environment without forming myelin in the PNS.