The central nervous system consists of the brain and the spinal cord. It is the body’s primary control and integration center, receiving sensory information, processing it, and issuing motor commands.

The brain is protected by the skull and by three layers of meninges; the spinal cord runs within the vertebral column and is similarly sheathed. Both are bathed in cerebrospinal fluid that cushions them and helps regulate the chemical environment. Ascending tracts in the spinal cord carry sensory signals toward the brain; descending tracts carry motor signals toward the muscles and glands. Reflex arcs can be completed within the spinal cord itself, allowing rapid responses without direct brain involvement.

Damage to the central nervous system is often permanent because mature neurons have limited capacity to regenerate. Stroke, trauma, multiple sclerosis, and neurodegenerative diseases all illustrate the consequences of disruption within this protected but vulnerable core. Research into spinal-cord repair and brain-computer interfaces continues to push the boundaries of what recovery might become possible.

Every deliberate movement, every perceived sensation, and every thought depends on the intact functioning of the central nervous system.