Innervated

Innervated refers to a tissue or organ that is supplied with nerve fibers, enabling neural control, sensation, or both. In physiology, innervation describes the pattern and extent of nerve supply to a structure, and tissues can be richly innervated, sparsely innervated, or comparatively avascular in terms of nerve presence. The term is often used to contrast with non-innervated or minimally innervated tissues.

Many organ systems rely on innervation for function. Skeletal muscles are innervated by somatic motor neurons, which stimulate contraction at neuromuscular junctions using acetylcholine. Cardiac muscle and most smooth muscles receive autonomic innervation, with sympathetic and parasympathetic fibers modulating heart rate, contractility, and tone of organs such as the gastrointestinal tract and blood vessels. The skin and joints are also richly innervated by sensory nerve fibers that convey touch, pain, temperature, and proprioception, as well as autonomic fibers that influence vasomotor activity and other functions.

Innervation develops through growth of neurites toward target tissues, guided by neurotrophic factors and signaling cues. The density and distribution of innervation can affect tissue sensitivity and responsiveness. Denervation, due to nerve injury or disease, can lead to loss of function, atrophy, or altered reflexes, while regeneration and reinnervation may restore function over time in some tissues.

Clinical relevance includes understanding nerve injuries, neuropathies, and conditions where altered innervation contributes symptoms. In research, measurements of innervation density help assess tissue health, aging effects, and responses to therapies intended to restore neural connections.