Gastrointestinal Physiology
Enteric nervous system
• lies in the wall of the gut (esophagus  anus)
• controls GI movement and secretions
• consists of 2 plexuses
o myenteric - peristalsis
o submucosal – secretion and (local) blood flow
• axon endings secrete acetylcholine which excites gastrointestinal activity, and norepinephrine, which inhibits it

Parasympathetic innervation
• cranial
o mouth & pharynx
o VAGUS nerve
 esophagus, stomach, pancreas and (somewhat) the intestines through the first half of the colon
• sacral
o via the pelvic nerves, innervate the lower half of the intestines
• postganglionic neurons in the plexuses cause  activity of the enteric nervous system

Sympathetic innervation
• originate between T-5 and L-2
• (most) preganglionic spinal neurons join the sympathetic chains and travel through peripheral ganglia, where their signals are dispersed to numerous neurons that spread throughout the gut
•......

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Title: Gastrointestinal Physiology
Approximate Word Count: 901
Approximate Pages: 4 (250 words per double-spaced page)

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