GLOSSARY

Nerves are bundles of axons in the peripheral nervous system, surrounded by connective tissue, that carry signals between the central nervous system (brain and spinal cord) and the rest of the body (skin, muscles, organs, and glands).

Structure

• Endoneurium: surrounds each axon.
• Perineurium: surrounds each fascicle (bundle of axons); the blood–nerve barrier.
• Epineurium: the outer covering of the whole nerve, carrying the blood vessels that nourish it.

Types

• By function: sensory (afferent), motor (efferent), and mixed (most nerves).
• By origin: cranial nerves (12 pairs) and spinal nerves (31 pairs).

Characteristics