Which statement describes white matter?

• A. Contains neuron cell bodies
• B. Contains autonomic neurons
• C. Contains sensory fibers only
• D. Contains myelinated axons

Answer: (D)

White matter is primarily made up of myelinated axons that form communication tracts linking different brain areas and the spinal cord. The myelin sheath, produced by oligodendrocytes in the CNS, speeds up signal transmission and gives white matter its pale color. Neuron cell bodies and synapses are concentrated in gray matter, where processing occurs. Autonomic neurons are typically located in gray matter regions or autonomic ganglia rather than within white matter. White matter includes both sensory (ascending) and motor (descending) tracts, so it isn’t limited to sensory fibers. The best description is that white matter contains myelinated axons.