BIOL 404-Exam 4-GI 15

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  1. What does pepsinogen do?
    • activated by acid to for pepsin
    • Pepsin digest protein
  2. What is the purpose of mucus and bicarbonate in the stomach?
    • lubricate and protect mucosa
    • Neutralize HCL at mucosal surface
  3. What does intrinsic factor do?
    Aid absorption of B12
  4. Describe how Parietal cells secrete acid:
    • CO2 diffuses into cell.
    • CO2 combines with H2O via carbonic anhydrase to produce carbonic acid
    • Carbonic acid dissociates into HCO–3 bicarbonate and H+
    • HCO–3 goes back to bloodstream.
    • An anion exchange molecule trades HCO–3 for Cl– (counter transport)
    • H+ is actively transported into gastric gland by the H+/K+ ATPase pump.
    • Chloride ions (Cl–) diffuse with the charged hydrogen ions.
    • Some potassium (K+) are counter transported into the cell in exchange for the hydrogen ions.
  5. How many chemical messengers control parietal cell secretion of acid?
  6. What are the four chemical messengers that control parietal cell acid secretion?
    • acetylcholine (ACh) – PNS stimulator
    • gastrin – a hormone
    • histamine – a paracrine agent
    • somatostatin – an inhibitory paracrine agent
  7. How does gastrin,somatostatin, histamine and ACh control Parietal cell acid secretion?
    Control H+/K+ ATPase pumps
  8. Gastric acid secretion happens in what three phases?
    • Cephalic
    • Gastric
    • Intestinal
  9. What is the first phase of gastric acid secretion?
  10. What is the second phase of gastric secretion?
  11. What is the third phase of gastric acid secretion?
  12. What phase of gastric acid secretion produced the largest proportion?
    Gastric phase
  13. During the cephalic phase, stimuli can increase activity of what division of the peripheral nervous system?
    Parasympathetic activity to the stomach’s enteric nervous system
  14. What chemical signalers are released plexus neurons in the GI during the cephalic pahse?
    • ACh
    • Gastrin
    • Histamine
  15. What are the two stimuli that increase gastric acid secretion during the gastric phase?
    • Distention of the stomach
    • Presence of amino acids and peptides (from protein digestion by pepsin)
  16. Gastric phase stimuli activated what part of the nervous system?
    Short and long neural reflexes
  17. What chemical signalers are released when neural reflexes are activated during the gastric phase?
    • ACh
    • Gastrin
    • Histamine
  18. Stimuli from what phases activate gastric ENS?
    Cephalic and gastric phase
  19. What can act directly on gastrin-producing cells to release gastrin?
    Amino acids and peptides
Card Set:
BIOL 404-Exam 4-GI 15
2013-05-02 21:42:03
BIOL 404 Exam GI 15

BIOL 404-Exam 4-GI 15
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