Which glial cells form myelin around axons in the human central nervous system?

Oligodendrocytes form myelin around axons in the human central nervous system.

Oligodendrocytes are glial cells found in the brain and spinal cord. Each cell can extend processes that wrap myelin around segments of multiple axons. Myelin is a lipid-rich insulating material that increases the speed and efficiency of electrical signaling along nerve fibers.

The gaps between myelin segments are called nodes of Ranvier. Electrical impulses appear to jump from node to node in a process known as saltatory conduction. This arrangement allows long-distance signals to travel rapidly without requiring every part of the axon membrane to depolarize at once.

Oligodendrocytes must be distinguished from Schwann cells. Schwann cells produce myelin in the peripheral nervous system, and an individual Schwann cell generally myelinates one axon segment. Astrocytes support neurons and help regulate their environment, while microglia act as resident immune cells. Diseases such as multiple sclerosis involve immune-mediated damage to myelin and can affect oligodendrocytes and central nervous system pathways.