Few body cells, lots of myelin

• A. White matter
• B. Neuron
• C. Peripheral nervous system
• D. Reflex action

Answer: (A)

White matter consists mainly of myelinated axons with relatively few neuron cell bodies. The myelin sheath, made by glial cells, insulates these axons and speeds electrical impulses along the nerve fibers through saltatory conduction. This high myelin content and scarcity of cell bodies give white matter its appearance and its role in rapid communication between brain regions and between the brain and spinal cord. In contrast, gray matter is rich in neuron cell bodies and dendrites, with less myelin. So the description “few body cells, lots of myelin” fits white matter. The peripheral nervous system also has myelinated fibers, but this statement specifically describes the white matter of the central nervous system. A reflex action is a rapid response and does not describe tissue composition.