Which of the following describes the composition of white matter in the spinal cord?

White matter in the spinal cord is primarily composed of bundles of myelinated axons. These myelinated axons are part of the central nervous system's communication pathways, allowing for the rapid transmission of nerve impulses. The myelin sheath, which surrounds these axons, serves as an insulating layer that enhances the speed of electrical conduction along the nerve fibers.

In contrast, gray matter, which contains neuron cell bodies, unmyelinated fibers, and some neural support cells, is found in the spinal cord and is responsible for processing and integrating information. The distinction between gray and white matter is critical for understanding the organization of the nervous system and how signaling happens between various regions of the body and the brain.

Therefore, recognizing that white matter consists of myelinated axons helps in understanding its function in terms of signal transmission and coordination within the central nervous system.