Lecture 30 - Regulation of Gastric Acid Secretion II Flashcards
What signals the feedback inhibition of gastric acid secretion in the antral region?
Presence of H+ ions in lumen
What are the two sites of feedback inhibition for gastric acid secretion?
Body/corpus, which is site of acid secretion
Antral region, which is site of gastrin secretion
What is involved in feedback inhibition of gastric acid secretion?
Somatostatin
What does the presence of H+ ions lumen stimulate in the antral region of stomach?
Stimulates somatostatin secreting cells (D cells) to produce somatostatin
What can somatostatin act as?
Paracrine hormone
- inhibits gastrin production by G cells
Endocrine hormone
- inhibits parietal cells
What is the G cells stimulated by in the antral region?
Digested proteins and amino acids
GRP
What are D cells stimulated by in antral region?
Luminal acid (H+)
Gastrin
What are D cells inhibited by in antral region?
ACh
What are G cells inhibited by in antral region?
Somatostatin
What is the feedback inhibition of acid secretion from the antral region?
Inhibition of acid secretion by events in the antral region - endocrine action - somatostatin
What is the function of somatostatin cells in body/fundus of stomach?
To produce somatostatin to limit acid secretion
How does somatostatin act as paracrine hormone?
- inhibits acid secretion by parietal cells
- inhibits ECL cells so reduces histamine production
The feedback inhibition of gastric acid secretion is
A. mainly dependent on gastrin.
B. entirely based on paracrine feedback.
C. independent of the stomach body region.
D. mainly facilitated by somatostatin
D. mainly facilitated by somatostatin
B- endocrine feedback
C - Dependent on stomach body region
What is the basal rate of gastric secretion?
25mL per hour
How does the cephalic phase stimulate secretion?
Via the parasympathetic nervous system (PNS)
How does the PNS regulate acid secretion?
Via ENS which in turn:
Directly stimulates parietal cells
Stimulates release of gastrin from antral region to blood
Stimulates histamine release from ECL cells
What controls gastric acid secretion in the gastric phase?
Stomach
What do receptors in stomach respond to in gastric phase?
Stretch (distention)
Products of digestion (antrum)
- increased peptides, decreased H+
How does stomach stimulate gastric acid secretion in gastric phase?
ENS - local reflex
External reflex involving the CNS (due to distention)
- vagovagal reflex
Gastrin and histamine
What controls gastric acid secretion in the intestinal phase?
Intestine
What is the effect of intestine control during the intestinal phase of gastric acid secretion?
Inhibit secretion via CCK, secretin and other duodenal hormones
What does the intestine respond to in the regulation of gastric secretion?
Distension
Increased [H+], Osmolarity, [Nutrients]
What is parallel to the secretion of gastric acid?
Secretion of pepsin
Gastric acid secretion is
A. increased in the intestinal phase.
B. regulated by acid and digestion products in the duodenum.
C. mainly driven by sight, smell and thought.
D. independent of the cephalic phase.
B. regulated by acid and digestion products in the duodenum.
- Duodenum releases CCK which switch off G cells
A - decreased
C - Not just cephalic phase
D - Dependent
