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Bundled nerve fibers outside the brain and spinal cord that carry sensory, motor, and autonomic signals to and from the body.
Medically reviewed & updated
Peripheral nerves are the cable-like bundles of nerve fibers that make up the peripheral nervous system (PNS)—everything outside the brain and spinal cord. They are the body's wiring, connecting the central nervous system to the skin, muscles, organs, and glands.
A peripheral nerve is built from many axons grouped together. Individual fibers are wrapped in connective tissue called endoneurium, gathered into bundles (fascicles) surrounded by perineurium, and the whole nerve is sheathed in epineurium, alongside its supplying blood vessels. Functionally, the PNS is divided into 12 pairs of cranial nerves, most arising from the brainstem, and 31 pairs of spinal nerves that emerge from the spinal cord (8 cervical, 12 thoracic, 5 lumbar, 5 sacral, and 1 coccygeal). Each spinal nerve is formed by the joining of a dorsal (sensory) root and a ventral (motor) root, then splits into dorsal and ventral rami that distribute to the body. In the limbs, ventral rami interweave to form networks called plexuses (such as the brachial and lumbosacral plexuses).
Peripheral nerves carry three kinds of traffic. Sensory (afferent) fibers bring information about touch, temperature, pain, and body position from the periphery toward the central nervous system. Motor (efferent) fibers carry commands from the spinal cord out to skeletal muscles to produce movement. Autonomic fibers travel within many of these nerves to regulate involuntary functions of internal organs. This makes peripheral nerves the essential intermediary between the central nervous system and the rest of the body.
Unlike central neurons, peripheral nerves can often regenerate after injury, though recovery is slow and sometimes incomplete. Damage—called neuropathy—can cause numbness, tingling, burning pain, or weakness; common causes include diabetes, compression (such as carpal tunnel syndrome), trauma, and infection. Patterns of deficit help localize whether a single nerve, a root, or a plexus is involved.
This information is educational and not a substitute for medical advice.