Extrinsic control of gastrointestinal function

The myenteric and submucosal plexuses confer a significant autonomy over motor and secretory functions of the gastrointestinal (GI) tract; however, robust parasympathetic inputs originating in the central nervous system (CNS) regulate motility and secretion. The parasympathetic vagus nerve is the Xth cranial nerve, with motoneurons contained within the dorsal motor nucleus and the nucleus ambiguus in the lower brainstem. The subdiaphragmatic branches of the efferent vagus innervate the GI tract from the lower third of the esophagus to the splenic flexure, including the liver and pancreas. The distal GI tract is innervated by parasympathetic inputs of the pelvic plexus. Sympathetic inputs are predominantly inhibitory modulating mucosal secretion and blood flow, with relatively minor effects on motility. These neurons arise in the lower thoracic (T6-T9, stomach and proximal GI tract) and lumbar (L2-L5; colon) spinal cord and reach their targets via postganglionic neurons located in the celiac, superior, and inferior mesenteric ganglia.