gastric secretions - intestinal phase

Question 1

stimuli for intestinal phase

Answer 1

intestinal gastrin - duodenum
enterooxyitin

Question 2

what do high levels or partially digested proteins in the duodenum stimulate

Answer 2

G cells to secrete gastrin (intestinal)
this moves through the blood to parietal cells, stimulating it to release HCl
also moves to chief cells to secrete more pepsinogen, which is converted to pepsin by Hcl

Question 3

secretin

Answer 3

secreted by S cells in response to:
- increased conc of protons
- increased conc of fatty acids

Question 4

secretin functions

Answer 4

• inhibits the release of gastrin, decrease stimulation of parietal cells, decreases release of HCl
• can act in the liver to convert cholesterol to bile
• can stimulate pacreatic ductal cells to secrete bicarbonate, reacts with protons to neutralise

Question 5

what do I cells respond to

Answer 5

respond to high conc of fatty acids
respond to peptones

Question 6

what do I cells secrete

Answer 6

cholecystokinin (CCK)
goes to parietal cells, inhibit release of HCl to slow emptying of stomach
can also enhance the action of secretin
can stimulate the gallbladder to contract and squeeze out concentrated bile
bind onto pancreatic acinar cells to release enzyme precursors

Question 7

what can high levels of chyme in the intestine stimulate

Answer 7

release of PYY
release of neurotensin
these inhibit HCl secretion from parietal cells, preventing excessive release of chyme

Question 8

what do K cells respond to

Answer 8

high conc of fatty acids
high conc of oligosaccharides
release GIP, goes to parietal cells, inhibits HCl secretion, can also prevent emptying of the stomach, has receptors on b cells of islets of langerhans, stimulates release of insulin

Question 9

what happens if Ach acts on parietal cells

Answer 9

continues to secrete HCl
chemoreceptors inactivate the vagues nerve to decrease HCl levels