CNS Anatomy

The CNS is the command center of the body. It is responsible for our sensory information, coordinating our movements and regulating bodily functions.

Neurons are the conducting cells of the nervous system. A typical neuron consists of

• Cell body: contains the nucleus and the surrounding cytoplasm
• Dendrites: short radiating processes
• Axon: one long process, which terminates in twiglike branches and may have branches projecting along its course.

Cell Body

In many ways, the cell body is similar to other types of cells. It has a nucleus with at least one nucleolus and contains many of the typical cytoplasmic organelles. It lacks centrioles, however. Because centrioles function in cell division, the fact that neurons lack these organelles is consistent with the amitotic nature of the cell.

Axons and Dendrites

An axon is a long, hair-like extension of a nerve cell that carries a message to another nerve cell.

Dendrites are thread-like extensions of the cytoplasm of a neuron that receive signals from other neurons. Typically, as in multipolar neurons, dendrites branch into treelike processes, but in unipolar and bipolar neurons, dendrites resemble axons.

Glial Cells

Glial (Neuroglial) cells do not conduct nerve impulses, but, instead, support, nourish, and protect the neurons. Glial cells are capable of mitosis.

There are three main sections to the Central Nervous System

• Meninges
• Brain
• Spinal cord

Meninges

There are three layers of meninges around the brain and spinal cord.

• The outer layer, the dura mater, is tough, white fibrous connective tissue.
• The middle layer of meninges is arachnoid, a thin layer resembling a cobweb with numerous threadlike strands attaching it to the innermost layer. The space under the arachnoid, the subarachnoid space, is filled with cerebrospinal fluid and contains blood vessels.
• The pia mater is the innermost layer of meninges. This thin, delicate membrane is tightly bound to the surface of the brain and spinal cord and cannot be dissected away without damaging the surface.

Meningiomas are tumors of the nerve tissue covering the brain and spinal cord. Although meningiomas are unlikely to spread, physicians often treat them as though they were malignant because symptoms may develop when a tumor applies pressure to the brain. A majority of the meningiomas are initially placed on active surveillance or watchful waiting until they become symptomatic.

Updated: September 23, 2026