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24 Cards in this Set
- Front
- Back
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Enteroendocrine cells have granules located on the _______ surface and secrete into the ________.
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basolateral
lamina propria |
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What are the 2 main functions of Gastrin and 5 main functions of CCK?
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Gastrin: promote H+ secretion; trophic factor for gastric mucosa.
CCK: contraction of gall bladder; trophic for pancreas and gall bladder; slow release of food (esp fats) from stomach; increase pancreatic secretion; induce satiety. |
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Name three key H+ inhibitory hormones in the GI system.
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Secretin
GIP (Gastrin Inhibitory Peptide) Somatostatin |
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Where do GIP (Gastrin Inhibitory Peptide) and GRP (Gastrin Releasing Peptide) come from?
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GIP: K cells in the duodenum and jejunum
GRP: Released by vagal nerve endings onto G cells (instead of ACh) |
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How do Secretin and CCK differ in their function on the pancreas?
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Secretin promotes secretion of lots of fluid and HCO3-, little enzymes.
CCK promotes secretion of lots of enzymes, less fluid. |
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What three secretagogues stimulate parietal cells to secrete H+? What are their receptors?
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ACh, Gastrin, Histamine
ACh -- muscarinic Gastrin -- CCK receptors Histamine -- H2 receptors |
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What kind of cells release histamine?
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ECL (Enterochromaffin-like) cells
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What is the "indirect pathway" for parietal cell secretion?
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ACh and Gastrin activate ECL cells, which secrete histamine onto parietal cells.
Also --> the vagus nerve may act on parietal cells directly, or it may act on G cells to release Gastrin (via GRP, not ACh). |
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What will block the effects of ACh on parietal cells? What about Histamine? What blocks the H+/K+ ATPase?
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ACh -- Atropine
Histamine -- Cimetidine Pump – Omeprazole |
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What are the two phases of acid production? What sets them off?
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Cephalic (contemplating food, smell, taste)
Gastric (presence of amino acids/small peptides, distention) |
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What do D cells release? What is the net effect of the release?
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Somatostatin
Inhibit acid secretion (and other hormones) |
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What happens to the acidity of the stomach when food enters?
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It falls (pH goes up) because food contains buffers. Acidity increases as food exits stomach.
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How are the gastric cells protected from the acid and pepsin?
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The alkaline HCO3-/mucous gel sits on cell surface.
Note: there is a Na+/2HCO3- symporter located on cell. |
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What is the term for stomach expansion for food storage? What mediates it?
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Accommodation
Mediated by the vagus nerve (receptive reflex: vago-vagal reflex) and ENS. Note: "vago-vagal" means vagus nerve is both afferent and efferent limb. |
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Saline meal, oleate (fatty) meal, acidic meal ...
Put these in order of gastric emptying rates. |
Saline meal (fastest emptying) --> acidic meal --> oleate meal (slowest emptying)
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What are the three actions of the stomach "grinding machine."
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propulsion
grinding retropropulsion Only particles <0.2 mm go to duodenum (except during migrating motor complexes). |
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What are PPIs?
What is one potentially harmful side effect of these? |
Proton Pump Inhibitors -- such as Nexium, inhibit acid secretion in the parietal cell.
One potential problem: since gastrin does not sense acid, it ups its production. Gastrin's trophic effect on the stomach my cause cancer if gastrin levels are increased (controversial). |
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The acini, islets of Langerhan, ducts. What are the proportions of each in the pancreas? Which is exocrine and which is endocrine?
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Acini: 84%
Ducts: 5% Islets: 1% Acini are exocrine; Islets are endocrine |
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In the pancreas, ______ cells secrete water, bicarbonate and sodium. ______ cells secrete enzymes.
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Duct
Acinar |
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What are the two major players in regulating pancreatic secretion? What type of cells do they come from? What initiates their action? What type of messenger system do they have? What cells do they act on? What gets secreted?
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CCK --> from I cells --> responds to presence of peptides, fatty acids, and certain amino acids --> act on acinar cells via IP3/Ca2+ 2nd messenger system --> results in secretion of enzymes.
Secretin --> from S cells in the duodenum --> responds to H+ or vago-vagal stimulation --> acts on ductal cells via cAMP 2nd messenger system --> results in the secretion of HCO3-, Na+ and H2O. |
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H+ is secreted in the lumen and HCO3- is secreted into the blood in _______. HCO3- is secreted in the lumen and H+ is secreted into the blood in ______.
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parietal cells (stomach)
ductal cells (pancreas) |
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Pancreatic secretion is intimately associated with _____, evidenced by the fact that vagotomy or atropine inhibits secretion.
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ACh regulation
NOTE:: Stimulation of acinar cells by CCK is not an endocrine effect, but nerve-dependent! (** at physiological levels --> extra high levels of CCK **WILL** act on acinar cells**) independent of ACh) |
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What is the only GI hormone needed for life?
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Intrinsic factor
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Bicarbonate secretion in the pancreas depends on a ______ antiport and a _____ channel on the luminal side.
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H+/HCO3-
Cl- |
