What are nerves?

• A. Bundles of axons in the peripheral nervous system
• B. Collections of neuron cell bodies in the Central Nervous System
• C. The brain
• D. Synapses

Answer: (A)

Nerves are bundles of axons in the peripheral nervous system. An axon is the long projection of a neuron that carries electrical signals. In the PNS, many axons travel together inside a nerve, enclosed by connective tissue layers—endoneurium around each axon, perineurium around small groups (fascicles), and epineurium around the entire nerve. This organization lets the nerve transmit sensory information from the body to the CNS and motor commands from the CNS to muscles and glands. Nerves can carry both sensory and motor signals, and may include autonomic fibers as well. In contrast, collections of neuron cell bodies in the central nervous system form gray matter or nuclei, and the brain is part of the CNS. Synapses are the junctions where neurons communicate with one another, not bundles of axons.