Gastric Secretion Flashcards
What are the five secretory products of the stomach?
H, pepsinogens, water, mucus, intrinsic factor
What two things do parietal cells makes?
IF and H
What does the pyloric mucosa secrete?
Gastrin
How does Carbonic Anyhydrase factor in H secretion?
It allows for the production of HCO3 which goes into the blood. To counteract this, Cl goes into the lumen, allowing the postive H to follow it.
What two substances break down the gastric mucosal barrier?
aspirin and alcohol (aspirin is a weak acid)
Into what structure is acid secreted within the parietal cell?
the intracellular canaliculi
What disappear in the parietal cell when the cell is stimulated
tubulovesicles
What ions are constant as H+ secretion increases?
Chloride
What ion decreases drastically within the stomach as H secretion increases?
sodium
Why does vomiting cause hypokalemia?
because the potassium levels in the stomach are higher than the body levels
What are the three triggers to acid secretion?
Acetylcholine, gastin and histamine
What is the chemical mediator of histamine in the stomach?
cAMP
What triggers histamine release?
Gastrin releases histamine from the enterochromaffin-like cell (ECL cell)
What is the chemical mediator of gastrin?
IP3
What is the chemical mediator of ach?
ip3
What is potentiation?
potentiation is the fact that the total acid released is higher than the inidivudal sums of each chemical . This occurs because each chemical triggers physiologic levels of secretion, but not max (so the three chemicals together increase production higher)
What drug (and mechanism) interferes with potentiatoin?
cimetadine targets the histamine receptor
When does gastrin secretion peak?
around midnight
What causes increased amounts of gastrin secretion?
the more you like a food, the more food you eat.
What percent gastrin secretion is based in the cephalic phase?
30%
What are the two modulators of the vagal nervous system that allow for parietal cell stimultaion?
Ach (which directly targets parietal cells)
GRP
In addition to the vagal fx that originate in the stomach, what else in the stomach causes increased acid secretion?
distension
Ach from the vagus nerve works on which two types of cells to regulate gastrin release?
Gastrin cell (through GRP) (gastrin cells are also secreted through digested proteins) Somatostatin cell (through Ach)
What are the actions of somatostatin?
Somatostatin directly targets the parietal cell to reduce acid secretion. It also indirectly reduces levels by inhibiting gastrin secretion. The somatostatin cells are stimulated by elevation in H.
