Harvard Human Anatomy - Nerves

Meninges

The membranes that envelop the central nervous system.

Dura mater

A thick membrane that is the outermost of the three layers of the meninges.

Pia mater

The innermost layer of the meninges.

Arachnoid mater

The layer interposed between the other two layers of the meninges.

Central nervous system

Comprises the brain and spinal cord. Does not include the cranial nerves or spinal nerves.

Peripheral nervous system

Includes the cranial nerves and spinal nerves. Does not include the spinal cord or brain.

Brain

Lies within the cranial cavity, surrounded by the skull.

Spinal cord

Lies within the vertebral canal surrounded by the spine (vertebrae) and intervertebral discs.

Motor neurons

Nerve cells that carry signals from the spinal cord to the muscles to produce (that is, effect) motion.

Sensory neurons

Send projections to other elements of the nervous system, ultimately conveying information to the brain or spinal cord.

Spinal nerves

Emerge from various segments of the spinal cord. There are 31 pairs total.

Cranial nerves

Leave and enter the cranial cavity through small passages in the skull.

Cerebrospinal fluid

A fluid that fills the space between the pia mater and the arachnoid mater.