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23 Cards in this Set
- Front
- Back
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Peristalsis - list 3 stimulus |
lumen distension lumen osmolarity digestion products |
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Peristaltic Reflex |
sensory neurons detect chemical/mechanical/pathological stimuli > EC cells in mucosa release 5HT > activates peristaltic and secretory reflex + vagal afferent to brain |
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Peristalsis can be abolished by.... |
- ganglionic blocking drugs - local anesthetics (block Na channels) - muscarinic blocker - opioids - stimulation of extrinsic postganglionic sympathetic - removing mucosa (no EC cells > no 5HT) |
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Increased sphincter tone / peristalsis is useful for...
Increased bowel movement is useful for.... (laxatives) |
- gastric reflux postoperative ileus and gastroparesis non-ulcer dyspepsia
- before sigmoidoscopy remove parasites counteract constipation easy defecation after hernia / head injury |
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Drugs which increase sphincter tone - list 3
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bethanechol
domperidone metoclopramide |
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bethanechol |
ACh mimitic - carbamyl group (long lasting) + methyl side chain (M>N)
*ACh contracts GIT
(increase sphincter tone)
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domperidone metoclopramide |
D2 blocker
*dopamine relaxes GIT
(block D2 to increase sphincter tone) |
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Drugs increasing peristalsis - list 2 |
5HT4 agonist - metoclopramide - cisapride
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metoclopramide cisapride |
(increase peristalsis) 5HT4 agonist - increase reflex sensitivity to luminal content
mechanism: - EC cells release 5HT > increased cAMP > easier to release ACh |
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How can clonidine affects peristalsis? |
clonidine stimulates alpha 2 receptors > reduced cAMP > more difficult to release ACh > reduced peristalsis |
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metoclopramide |
(increase peristalsis)
D2 blocker
weak 5HT4 agonist 5HT3 blocker at high dose
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Motilin - where release - what effect |
(increase peristalsis)
22 AA
released from upper GI endocrine mucosa
released in fasting state to stimulate motility
accelerates gastric emptying (via smooth muscle receptors, NOT blocked by tetrodotoxin / muscarinic blockers)
*Erythromycin - antibiotic which stimulates motilin receptors
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Which antibiotic is a potent agonist of motilin receptors? |
Erythromycin |
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Ghrelin - where release - what effect |
(increase peristalsis)
released from stomach
increase feeding and weight gain (via GHRH-R: growth hormone secretagogue receptor > increased GH)
cholingergic and tachykinergic (tachykinin) > increased peristalsis |
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Increased bowel movement is useful for.... (laxatives) |
- before sigmoidoscopy remove parasites counteract constipation easy defecation after hernia / head injury |
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Laxatives - list 4 types |
1 bulk laxative - wheat bran , flatulence
2 osmotic laxative - Magnesium sulphate, sodium sulphate
3 Stimulant laxative - bisacodyl, phenolphalein, sennatoside
4 Lubricant laxative - sodium dioctyl sulphosuccinate, liquid paraffin |
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1 bulk laxative |
- increase volume in lumen - absorb 100x water - 1-3 day
wheat bran, methylcellulose, bassorin, metamucil, flatulence |
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2 osmotic laxative |
- poorly absorbed salts > draws water
Magnesium sulphate, sodium sulphate
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3 stimulant laxative |
bisacodyl, phenolphalein, sennatoside
- stimulate sensory nerve endings in mucosa / myenteric plexus > ion secretion by NA/K ATPase
- increase PG synthesis - increase cAMP > secretion and motility |
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4 lubricant laxative |
sodium dioctyl sulphosuccinate - draws water into faeces
liquid paraffin - a mixture of aliphatic hydrocarbons - softens stools |
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List 3 anti-diarrheal drugs |
Charcoal / Kaolin / Dioctahedral smectite - increase surface area
Bismuth salicylate - anti-bactericidal, inhibits COX
Opioids - codeine, loperamide, diphenoxylate ("高登老板話咪帶份notes泥") |
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Opioids as anti-diarrheals |
codeine loperamide, diphenoxylae
opioids reduce cAMP levels (via m & k receptors) |
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Do NOT use anti-diarhoeal drugs casually in.... |
babies or pregnant women!
dangers: intestinal obstruction, coma can be fatal! |
