Which tissue is characterized by the presence of myelinated axons?

• A. White matter
• B. Grey matter
• C. Cerebellum
• D. Brainstem

Answer: (A)

White matter is the tissue characterized by myelinated axons, which speeds neural signaling through saltatory conduction as impulses jump between nodes of Ranvier. In the central nervous system, oligodendrocytes produce the myelin sheath, and the lipid-rich myelin gives white matter its pale appearance. By contrast, gray matter contains mainly neuronal cell bodies, dendrites, and synapses with relatively little myelin, giving it a darker color. Structures like the cerebellum and brainstem include both white and gray matter, but the presence of abundant myelinated axons specifically defines white matter.