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.