Extrinsic innervation

Abstract

The autonomic nervous system makes widespread connections with the gastrointestinal tract and electrical stimulation of the nerve bundles innervating the various gut regions have profound effects on motility. Yet removal of the extrinsic nerve supply has in most regions only a limited effect on motor activity. Only in the upper oesophagus and the external anal sphincter, where the motor function is performed by striated muscle, is there total loss of muscular contractility when the parasympathetic supply is disrupted. The rest of the gastrointestinal tract, being composed of smooth muscle with its own intrinsic nerve supply, does not show this absolute dependence on its motor innervation. Instead, denervation is followed, at worst, by a transient period of disorganized activity lasting from a few days to several weeks during which time there is a gradual return to normal activity.