Biology 30 Nervous System Practice Exam 2026 – Complete Study Guide

In the peripheral nervous system, myelin is formed by Schwann cells. They wrap around a single axon segment to create the myelin sheath, which insulates the fiber and speeds signal transmission through saltatory conduction. By contrast, oligodendrocytes in the central nervous system myelinate multiple axons, while astrocytes and microglia serve support and immune roles rather than producing myelin in the PNS. So the glial cells responsible for forming myelin in the peripheral nervous system are Schwann cells.