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Physiology_Ch. 62
Nervous System Control of GI Function
| Question | Answer |
|---|---|
| What are the 3 layers of smooth muscle found in the intestinal wall (from superficial to deep)? | Longitudinal, circular, and mucosal |
| What structure is located between the longitudinal muscle layer and the circular muscle layer (located near the outside of the intestinal smooth muscle wall)? | Myenteric nerve plexus |
| What nervous system structure is located in the submucosal layer of the intestinal wall (located closer toward the center lumen)? | Meissner's plexus (submucosal nerve plexus) |
| What is the length and width of the smooth muscle fibers of the GI tract? | 200-500 micrometers long and 2-10 micrometers wide |
| GI smooth muscle fibers are generally in bundles. How many fibers are typically in a bundle? | 1000 fibers |
| What electrically connect each muscle cell in GI smooth muscle? | Gap junctions |
| Each muscle layer is a latticework of bundles. How do these muscle layers function? | Function as a syncytium |
| What are slow waves? | Gradual changes in the resting potential of the smooth muscle fibers |
| What are the slow wave frequencies in the stomach, duodenum, ileum, and colon? | Stomach: 3/minute; duodenum: 10-12/minute; ileum: 8-9/minute; colon: 3/minute |
| What is the myenteric plexus? | Chain of interconnected neurons that extends the entire length of the GI tract |
| What does the myenteric plexus control? | Rate and strength of muscle contraction along the length of the gut (peristalsis) |
| What does the submucosal plexus control? | Controls contraction of the submucosal muscles, causing infolding of the mucosa - thus controlling the rate of secretion, absorption, and blood flow |
| There are numerous neurotransmitters used with respect to the myenteric and submucosal nerve plexuses. Name some of them. | Serotonin, dopamine, NO, substance P |
| The GI tract is under parasympathetic and sympathetic autonomic control. Cranially, parasympathetic innervation is primarily via the __________. | Vagus nerve |
| To what parts of the GI tract does the vagus nerve provide parasympathetic innervation? | Primarily to esophagus, stomach, and pancreas, and somewhat less to the small intestine and proximal half of the large intestine |
| What type of fibers make up most (80%) of the vagus nerve? | Afferent fibers |
| The GI tract is under parasympathetic and sympathetic autonomic control. Caudally, parasympathetic innervation is via the ___________. | Pelvic nerves |
| To what parts of the GI tract do the pelvic nerves provide parasympathetic innervation? | Distal half of the large intestine |
| Where are the post-ganglionic neurons of the GI tract located? | Within the myenteric and submucosal plexuses |
| Are most of the parasympathetic neurons excitatory or inhibitory? | Excitatory |
Created by:
Cory67
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