OG

Question 1

3 phases of gastric acid secretion

Answer 1

1. Cephalic phase (smell/taste)
   - 30% of gastric acid production from parietal cells
   - vagal cholinergic stimulation causing HCL and gastrin release from G cells
2. Gastric phase (distension of stomach)
   - 60% acid production
   - stomach distension, low H+, peptides causes gastrin release
3. Intestinal phase (food in duodenum)
   - 10% acid production
   - high acidity, distension, hypertonic solutions in the duodenum inhibits gastric acid secretion via enterogastrones (CCK, secretin) and neural reflexes

Question 2

Source (cells) and action of Gastrin

Answer 2

• G cells in the antrum of the stomach
• Increase HCL, pepsinogen and IF secretion
• increases gastric motility
• trophic effect on gastric mucosa

Question 3

Source (cells) and action of CCK

Answer 3

• I cells in small intestine
  Actions
• Increases secretion of enzyme-rich fluid from pancreas
• contraction of gallbladder and relaxation of sphincter of Oddi
• decreases gastric emptying
• trophic effect on pancreatic acinar cells
• induces satiety

Question 4

Source (cells) and action of Secretin

Answer 4

• S cells in upper small intestine
  Actions
• Increases secretion of bicarbonate-rich fluid from pancreas and hepatic duct cells
• decreases gastric acid secretion
• trophic effect on pancreatic acinar cells

Question 5

Source (cells) and action of VIP

Answer 5

• Small intestine, pancreas
  Actions
• Stimulates secretion by pancreas and intestines
• inhibits acid and pepsinogen secretion

Question 6

Source (cells) and action of Somatostatin

Answer 6

• D cells in the pancreas and stomach
  Actions
• Decreases acid and pepsin secretion
• Decreases gastrin secretion
• Decreases pancreatic enzyme secretion
• Decreases insulin and glucagon secretion
• Inhibits trophic effects of gastrin,
• Stimulates gastric mucous production