Nerves: Specialized cells that use chemical reactions to send impulses from the body tissues to the spinal cord and brain (also known as peripheral nerves).

Nerve root: One of the two nerve bundles (anterior and posterior) emerging from the spinal cord that join to form a segmental spinal nerve.

Nervous System: The system of nerves including the brain, cranial nerves, spinal cord, spinal nerves, and peripheral nerves; includes the autonomic (sympathetic and parasympathetic) nerves.

Nociceptors: The relatively unspecialized and uninsulated nerve cell endings that initiate and transmit the sensation of pain to the brain for interpretation. (noci- is derived from the Latin for “hurt” or “injure”)

Normal: A range or zone that represents healthy functioning and which will vary among different groups or classification such as: age, sex, and other factors such as environmental conditions.

Nucleus pulposus: Spongy gel-like center of a spinal disc.