Innervaation

Innervation, sometimes spelled innervaation, is the distribution or supply of nerves to a body part, enabling sensation, motor control, and autonomic regulation. It encompasses both the sensory (afferent) pathways that convey information to the central nervous system and the motor (efferent) pathways that originate in the CNS to stimulate muscles or glands. Autonomic fibers regulate involuntary functions such as heart rate, digestion, and glandular activity.

There are two broad kinds of innervation. Somatic innervation supplies skeletal muscle and the skin, providing voluntary movement and conscious sensation. Motor neurons send signals from the brain or spinal cord to muscles, while sensory receptors in the skin, joints, and other tissues relay touch, pain, temperature, and proprioceptive information back to the CNS. Autonomic innervation governs the function of smooth muscle, cardiac muscle, and glands. It includes the sympathetic and parasympathetic divisions, often with complementary or opposing effects, and it may involve enteric circuits in the gastrointestinal tract.

Anatomically, nerves arise from spinal nerve roots and cranial nerves and may form plexuses that distribute to limbs and trunk. Peripheral nerves branch into smaller fibers that reach specific organs or regions, with dermatomes describing skin innervation by spinal nerves and motor maps aligning to muscle groups. Autonomic innervation follows distinct routes such as the sympathetic chain or cranial autonomic nerves.

Clinically, loss or disruption of innervation can cause numbness, weakness, or paralysis in the affected tissues. Denervation can lead to atrophy and altered function, while reinnervation or nerve regeneration may restore some function. Diagnostic tools include nerve conduction studies, electromyography, and imaging to assess the integrity of neural supply. Understanding innervation is essential in anatomy, neurology, and surgery.