In the central nervous system the myelin sheath is produced by oligodendrocytes. A single oligodendrocyte can extend processes to dozens of nearby axons and wrap each with a segment of compact myelin, leaving the nodes of Ranvier exposed for saltatory conduction.

Myelination begins in development and continues for years in humans, particularly in association tracts. Oligodendrocytes also provide metabolic support to the axons they ensheath. When they are damaged, as in multiple sclerosis or white-matter stroke, conduction slows or fails and axons themselves may degenerate.

Precursor cells persist in the adult brain and can generate new oligodendrocytes, offering a limited capacity for repair. Research into the signals that control oligodendrocyte differentiation and myelin wrapping aims to enhance remyelination in demyelinating diseases. The intimate physical and metabolic relationship between oligodendrocyte and axon makes these cells essential partners in long-range neural communication.

Without oligodendrocytes, the rapid, energy-efficient signaling of the vertebrate brain would be impossible.