Regulation of gastric acid secretion (missed out page part)

Question 1

What phases are involved with the secretion of gastric juice?

Answer 1

Phases involved:

1. Cephalic phase
2. Gastric phase
3. Intestinal phase

Question 2

What regulates HCl secretion?

Answer 2

HCl secretion is regulated by neuronal pathways and duodenal hormones

How do they do that?

1. Direct pathway, acting on parietal cells → ↑ acid secretion
2. Indirect pathway, influence the secretion of gastrin and histamine → ↑ acid secretion

Question 3

Describe the cephalic phase

Answer 3

Cephalic phase (meal times- smell, sight, taste, chewing): ACh and gastric release

• ACh stimulates histamine release from ECL cells
• ACh acts directly on parietal cells → HCl secretion
• Gastric stimulates histamine release from ECL cells
• ACh acts directly on parietal cells → HCl secretion

Question 4

Describe the Gastric phase

Answer 4

• Gastric phase (distension of stomach; ↑ peptide concentration): ↑ acidity (↑[H+]) - important quantitatively
• Acid secretion decreases as the acidity of the lumen increases

Question 5

Describe the effects of protein content on a meal of H+ secretion

Answer 5

• Acidity of lumen of stomach is ↑ before a meal (no buffers)
• More proteins → ↑ peptides in stomach (↑ gastrin secretion)

Question 6

What do proteins do to luminal acidity?

Explain the mechanism

Answer 6

• Proteins act as buffers in the gastric lumen
• And so what? HCl secretion increases
• H+ + proteins → ↓ [H +]; protein acts as a buffer; proteins remove the inhibitory powers of HCl on gastrin secretion and hence acid secretion
• But…
• This then increases gastrin-mediated acid secretion