Nervperifer

Nervperifer, commonly called the peripheral nervous system, includes all neural elements outside the brain and spinal cord. This comprises cranial nerves, spinal nerves with dorsal and ventral roots, peripheral ganglia, and the networks formed by these fibers, as well as autonomic nerves and ganglia. It connects the central nervous system to muscles, glands, and sensory receptors, enabling sensation, movement, and autonomic regulation.

Structure: Nerve fibers are enclosed by endoneurium around each axon, perineurium around fascicles, and epineurium around the whole nerve. The vasa nervorum supply blood. Axons may be myelinated by Schwann cells; conduction velocity increases with myelination and diameter. Peripheral nerves contain sensory, motor, and autonomic fibers, often in mixed bundles.

Function: Sensory fibers convey touch, pain, temperature, and proprioception; motor fibers innervate skeletal muscles; autonomic fibers regulate heart rate, digestion, and glandular activity. Transmission uses saltatory conduction on myelinated fibers and slower conduction in unmyelinated C fibers.

Clinical relevance: Disorders include mononeuropathies such as carpal tunnel and polyneuropathies such as diabetic neuropathy, neuritis, nerve compression, or trauma. Symptoms depend on affected fibers and can include numbness, tingling, weakness, muscle atrophy, or autonomic dysfunction. Diagnosis relies on history, neurologic examination, nerve conduction studies, EMG, imaging, and sometimes biopsy. Treatment targets the underlying cause and may involve pain management, physical therapy, splinting, or decompression.

Regeneration: The peripheral nervous system has some regenerative capacity. After injury, Wallerian degeneration occurs; axons may regrow along the distal stump guided by Schwann cells, with recovery depending on distance and environment; complete recovery is not guaranteed.