Section 6. Brain, Spinal Cord, and Nerve Disorders

Chapter 95. Peripheral Nerve Disorders

Topics: Introduction | Disorders of Muscle Stimulation | Disorders of the Neuromuscular Junction | Plexus Disorders | Thoracic Outlet Syndromes | Mononeuropathy | Mononeuritis Multiplex | Polyneuropathy | Hereditary Neuropathies | Spinal Muscular Atrophies

Introduction

The peripheral nervous system includes all the nerves outside the central nervous system, that is, all the nerves outside the brain and spinal cord. The nerves that connect the head, face, eyes, nose, muscles, and ears to the brain (cranial nerves (see Section 6, Chapter 96)) and the nerves that connect the spinal cord to the rest of the body, including the 31 pairs of spinal nerves, are part of the peripheral nervous system.

See the figure Using the Brain to Move a Muscle.

Dysfunction of peripheral nerves may result from damage to any part of the nerve: the axon (the part that sends messages), to the body of the nerve cell, or to the myelin sheath (the membranes that surround the axon, enabling nerve impulses to travel quickly (see Section 6, Chapter 92)). If motor nerves (which stimulate muscle action) are damaged, muscles may weaken or become paralyzed. If sensory nerves (which carry sensory information) are damaged, abnormal sensations may be felt or sensation may be lost.