What is white matter in the brain and spinal cord primarily composed of?

White matter in the brain and spinal cord is primarily composed of axons, which are the long, slender projections of neurons that transmit electrical impulses away from the cell body. These axons are often myelinated, meaning they are insulated with a fatty substance called myelin, which enhances the speed and efficiency of signal transmission between different parts of the nervous system.

This myelination is what gives white matter its characteristic color, as opposed to gray matter, which is composed mainly of neuronal cell bodies and dendrites and lacks this extensive myelin content. The presence of axons in white matter is essential for communication between various brain regions and between the brain and spinal cord, facilitating complex neural networking necessary for motor control and sensory processing.

In contrast, cell bodies, dendrites, and neurotransmitters serve different roles within the nervous system, contributing to the overall function but not specifically forming the primary structure of white matter. Understanding the composition of white matter is crucial for grasping the organization and functionality of the central nervous system.