Gastrointestinal Physiology (con'd) Flashcards
What is the cephalic phase?
Vagus nerve (thinking about, smelling, or tasting food) stimulates the ENS to produce acid, gastrin and HCl, and Histamine
this occurs before you eat
Prepartory process
what is the negative feed back mechanism if pH is too low?
causes D cells to release somatostatin which inhibit G cells, ECL cells, and parietal cells
what is the gastric phase?
when food is present in stomach triggers gastointestinal reflex. Baroreceptors detect enlargment of stomach and chemoreceptors respond to food (sent via vagus nerve), stimulating goblet cells, parietal cells, G cells and chief cells
what happens to food when the pH gets too low?
movement of food slows down
what is the intestinal phase?
signal coming from the intestine to prepare for incoming food
what is the enterogastric reflex?
signal from intestine snt to stomach. chemoreceptors detect pH and good contents, causing hormone secretin to be secreted.
what does secretin do?
inhibits gastric function via parietal/chief cell
what other molecules inhibit stomach function which is stronger
gastric inhibitory peptide (GIP) - stronger
cholecystokinin
what does the D cell do?
secretes somatostatin in response to H+ which acts on G cell, parietal cell, and ECL cells
what are the two classes of drugs that prevent acid secretion? which is irreversible?
H2 blockers
proton pump inhibitors (irreversible)
why are NSDAIDs bad for the stomach?
prevents prostaglandin synthesis
why are NSDAIDs bad for the stomach?
prevents prostaglandin synthesis which regulated gastric secretion
what are two 2 COX enzymes?
constitutive COX 1
inducible cox 2
what is the difference between cox 1 and cox 2?
cox 1 - works all the time and makes a low, protective dose of PG
cox 2 - makes no PG when turned off, but makes a lot when turned on (pro inflammatory)
what is the difference between 1st and 2nd generation NSAIDs?
1st - non specific (block both cox 1 and cox2)
snd - block cox 2 only
what is a downside to 2nd generation NSAIDs?
can cause heart attack
what are NO-NSAIDs?
Nitric oxide NSAIDs (modified NSAID)
have nonselective COX inhibition and NO release causes vasodilation (protective)
CINODs are also non-specific
what is the difference between endocrine and exocrine pancreas?
endo - pancreatic islets
exo - pancreatic duct
how much pancreatic juice is secreted a day?
1500ml/day
what are the two components of pancreatic juice?
1) aqueous which has Na-HCO3 solution (buffer stomach pH)
2) enzyme - proteolytic enzymes (zymogens), pancreatic amylase/lipases
what 3 things control pancreatic secretion?
vagus nerve
cholecystokinin
secretin
how does the vagus nerve control pancreatic secretion?
activates Ach? (parasym) which is excitatory and promote excretion or NE (sym) which inhibits secretion
how does cholecystokinin control pancreatic secretion?
detects lipids and has positive effect on pancreas but negative effect on stomach
also decreases gastric emptying
how does cholecystokinin control pancreatic secretion?
detects lipids and has positive effect on pancreas but negative effect on stomach
also decreases gastric emptying
how does secretin affect pancreatic secretion?
when acidic contents reach the stomach, it causes secretin release which acts on pancreas to increase aqueous secretion
also decreases gastric emptying
what is the function of the liver?
continually produce bile