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22 Cards in this Set
- Front
- Back
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In peristaltic reflexes, what neurons lead to contraction of both circular and longitudinal muscles?
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ACh/TK mediated excitatory motor neurons
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In peristaltic reflexes, what neurons lead to relaxation of both circular and longitudinal muscles?
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1) Nothing does both.
2) Individually, Relax circ muscle: VIP/NOS inhibitory neurons Relax long muscle: inhibit ACh/Tk excitatory motor neurons |
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Explain the sensory (afferent) limb of peristalsis:
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1) Mucosal Reflex: short chain FAs, HCl, bile acids and distortion of villi - stimulate release of seratonin from enterochromaffin cells - binds 5-HT4 receptor on intrinsic primary afferent neuron (IPAN) - IPAN releases calcitonin gene-related peptide (CGRP) and substance P - interneurons in short arc reflex are activated
2) Axon Collateral/Distension Reflex: distension of gut - extrinsic afferent CGRP neuron activated in dorsal root ganglion - activates peristaltic reflex pathway (pathological probably) |
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What happens when the mucosal reflex and axon collateral (distension) reflex are both activated?
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The potentiate eachother (synergize) to produce an even greater effect than the sum!
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How far do peristaltic waves travel before they die out?
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only a few centimeters
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What is the slow wave rate in the small intestine?
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duodenum - 12/min
dereasing anally ileum - 8/min * this moves chyme toward ileocecal sphincter |
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Name and describe the 3 phases of the Migrating Myoelectric Complex (MMC).
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Phase I - period of quiescence (45-60 mintues)
Phase II - increasing contractile activity; slow waves have more APs Phase III - almost every slow wave has APs and muscle is contracting intensely (10 minutes) |
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Where does the MMC begin and how long does it last?
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1) in the stomach
2) every 75-90 minutes |
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What is the purpose of MMC?
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clear the SI clear of secretions and chyme; may allow large particles to pass; motilin may be involved
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What happens to MMC when one ingests a meal?
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Segmentation in the small intestine begins (and is continuous).
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Name the intestinal reflexes.
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Both are long arc:
1) Intestino-intestinal -- digestion in one area, inhibit another (prevents blockage of mvmt) 2) Gastro-Ileal -- coordinates ileum and stomach * both act finally thru ENS |
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Name two muscular specialities of the large intestine.
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1) longitudinal muscle - tenia coli
2) circular muscle - haustra |
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What are the 2 motility patterns in the large intestine?
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1) Mixing mvmts/local contractions
2) Mass mvmts |
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In what direction do local contractions in ascending colon often move?
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antiperistaltic - anal to oral; delay mvmt of feces into transverse colon
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Normal function of mixing movements/local contractions?
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1) push feces toward cecum
2) absorb water and electrolyte |
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Where do mass movements begin?
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transverse colon
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How often do mass movements occur?
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1-2 times a day
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What does the colono-colonic reflex do?
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distension of one region of the colon while another region relaxes
* mediated by the sympathetic NS |
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What does the gastro-colonic reflex do?
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distension in the stomach increases the motility in the colon and increases the mass mvmts to prepare colon for food
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What are the 2 colonic reflexes?
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1) colono-colonic reflex
2) gastro-colonic reflex * both are long arc |
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Explain the Defecation Reflex.
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1) stretch receptors in rectum activated
2) reflex initiated by enteric n. and pelvic n. to smooth muscle and by pudendal nn. to skeletal muscle (EAS) 3) rectum contracts 4) IAS relaxes, EAS contracts 5) neural inputs from CNS reinforce or inhibit these signals |
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Is there net forward movement in segmentation contractions in the small intestine?
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NO!
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