Gastric Secretion - Prunuske Flashcards
Why would bezoar be the best possible name for your pet cat?
Bezoar is a ball of foreign material trapped in the stomach (like a hairball)
In human, the migrating motor complex is going to get that cleared for you.
That’s why it would be a hilarious name for a cat, just saying
What is dyspepsia?
Indigestion
Pain in upper abdomen after eating
What is trituration?
Grinding food into small molecules
What is scintigraphy?
Test using dual-radiolabeled sold/liquid meal to measure gastric emptying
Where is gastrin secreted from? What does it do?
Gastrin secreted from G cells in antrum of stomach. Causes parietal cells in the fundus/body of the stomach to secrete HCl
When is gastrin secreted from G cells in the antrum?
Where does it bind parietal cells in the body/fundus?
Food and stomach distention causes vagal stimulation.
Vagal stimulation stimulates the G cell through the GRP nerve to secrete gastrin.
Gastrin binds on the CCK2 receptor of parietal cells
Gatrin acts directly on parietal cells, but it also acts indirectly to stimulate HCl release. How?
It acts on ECL cells inducing histamine release. Histamine then acts on parietal cells to cause HCl secretion
How does acetylcholine affect gastric acid release from parietal cells?
Hint: 3 ways
3 ways
1 - ACh binds muscarinic receptors on the parietal cell
2 - ACh activates ECL cells to release histamine, which acts on parietal cells
3 - Activate enteric neurons to release GRP, stimulating G cells to release gastrin, gastrin stimulates parietal cells
So let’s get down to the nitty gritty. Once there is a stimulus on the parietal cell itself. What is the mechanism by which it begins secreting HCl?
In the resting state there are caniculi channels and many H/K ATPase channels loaded into vesicles that are sitting int he cytoplasm.
Upon acitvation, these vesicles all fuse with the membrane.
Shazam! You’ve got tons of these channels in the apical membrane spitting out Hydrogen ions
What causes the alkaline tide in the bloodstream when acid is being secreted from parietal cells?
Cl/HCO3 exhangers on the basolateral side of the cell are pulling HCO3 into blood as Cl is pushed toward the lumen to form HCl along with the hydrogens being pumped out.
All this HCO3 can create an alkaline tide
When is somatostain released?
What is its function?
Released from D cells when the pH < 3
(during gastric phase, you’ll see less somatostatin as the pH rises)
Somatostatin INHIBITS:
- G cell release of gastrin
- Formation of cAMP in parietal cells
- ECL secretion of histamine
What inhibitory fxn do enterogastrones like secretin, CCK, GLP-1, and GIP have?
Stop ECL cell from releasing histamine
Describe the 4 phases of gastric secretion: Interdigestive Cephalic Gastric Intestinal
Interdigestive: Low acid secretion, D cells release somatostatin to keep gastrin low
Cephalic: Dorsal vagal complex integrates input from higher centers to activate vagus nerves. GRP activates gastrin release and ACh activates ECL and parietal cells.
Gastric: Stomach distention activates vagal afferents and the enteric nervous system. Amino acids activate gastrin secretion and food raises pH, decreasing somatostatin secretion
Intestinal: Intro of the gastric contents into the small intestines activates duodenal G cell secretion of gastrin. Activation of secretin (+ other enterogastrones) and neural reflex decreases secretion of HCl
Megaloblastic anemia and neurological problems can be caused by autoimmune destruction of which cells?
What kind of hypersensitivity rxn is this? (just good review)
Parietal cell destruction. (They secrete instrinsic factor.
Will lead to pernicious or megaloblastic anemia.
Type 2 Hypersensitivity Rxn
AND
Type 4… both i think
Pepsinogen is an inactive protease.
How is it converted to the active form?
How and where is it secreted in the first place?
What’s the active form for?
Pepsiongen is activated to the powerful protelytic enzyme PEPSIN by acid environment.
Pepsinogen secreted by chief cells is response to acetylcholine and gastrin. (inhibited by secretin)
