BIOL 404-Exam 4-GI 16

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kyleannkelsey
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217324
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BIOL 404-Exam 4-GI 16
Updated:
2013-05-02 17:42:42
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BIOL 404 Exam GI 16
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BIOL 404-Exam 4-GI 16
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  1. What can be caused by high concentrations of acid in the lumen of the stomach and duodenum?
    Ulcers in the mucosa
  2. What negative feedback mechanisms control acid secretion?
    • H ions stimulate the release of somatostatin inhibiting acid secretion
    • Somatostatin inhibits secretion of gastrin and histamine
    • Intestinal phase mechanisms also feedback to inhibit acid secretion
  3. Histamine has a positive or negative effect on parietal cell acid secretion?
    Positive
  4. Somatostatin has a positive or negative effect on parietal cell acid secretion?
    Negative
  5. Gastrin has a positive or negative effect on parietal cell acid secretion?
    Positive
  6. Gastrin has a positive or negative effect on Histamine secretion?
    Positive
  7. HCL has a positive or negative effect on parietal cell acid secretion?
    Negative
  8. HCL has a positive or negative effect on Somatostatin secretion?
    Positive
  9. What stimuli in the small intestine provoke negative feedback on gastric acid secretion?
    • Luminal distension
    • H+
    • Hypertonic solutions
    • Products of digestion
  10. What type of pathways invoked by the Intestinal phase inhibit gastric acid secretion?
    • Long and short reflex arcs
    • Local actiivities
    • Secretion of secretin, CCK and GIP hormones
  11. When the pH is less than 2 in the small intestine, What happens?
    The vagal nerve is stimulated and the medulla oblongata inhibits gastric acid secretion
  12. How do GIP, CCK and Secretin get from the duodenum to the stomach?
    Circulation
  13. How is pepsinogen secretion controlled?
    • Long and short reflex arcs
    • Similar factors as Gastric acid
  14. how is pepsinogen activated?
    By HCL
  15. What is a proenzymes or zymogens?
    inactive enzyme precursors
  16. What is the term for an inactive enzyme precursor?
    Proenzymes or Zymogens
  17. What is the purpose of producing zymogens instead of active enzymes?
    Protects cellular components from digestion
  18. What is the change from pepsinogen to pepsin catalyzed by?
    Nothing, it is an autocatalytic process
  19. Acidity activated pepsinogen in what way?
    Alters its shape to expose the active site
  20. Do all pepsinogen molecules need to be activated by HCL?
    No only one, the rest can be activated by pepsin
  21. Gastric acid secretion is stimulated by what?
    protein digestion products in the lumen of the stomach.

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