Which cell type forms myelin in the central nervous system?

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

Answer: (A)

Oligodendrocytes are the cells responsible for forming myelin in the central nervous system. They extend their processes to wrap around portions of multiple axons, creating the multilayered myelin sheath that electrically insulates axons and speeds up nerve impulse conduction through saltatory conduction. One oligodendrocyte can myelinate several nearby axons, which is characteristic of CNS organization. In contrast, Schwann cells perform myelination in the peripheral nervous system and typically wrap around a single axon segment. Astrocytes support neurons and help maintain the extracellular environment, while microglia act as immune cells within the CNS. In pathology, loss or damage to oligodendrocytes leads to demyelination in the CNS, as seen in diseases such as multiple sclerosis.