chapter 20b gastro Flashcards
GI function is regulated to
maximize absorption, regardless of whether nutrients are need
regulation of GI function is ___ based on concept of homeostasis
NOT
reflexes mediated through the ____ control many GI functions
enteric nervous system
___ is paired with enteric nervous system to control GI
ANS
stimulates gastric secretion and motility, stimulates ileal motility and relaxes ileocecal sphincter, stimulates mass movement of colon
gastrin (stomach)
inhibits gastric secretion and motility, potentiates actions of secretin on pancreatic bicarbonate secretion stimulates pancreatic enzyme secretion, stimulates bile secretion by liver, stimulates gallbladder contraction and relaxation of sphincter of Oddi
cholecystokinin CCK (duodenum and jejunum)
inhibits gastric secretion and motility, stimulates pancreatic bicarbonate secretion potentiates actions of CCK on pancreatic enzyme secretion, stimulates bile secretion by liver
secretin (duodenum and jejunum)
inhibits gastric secretion and motility, stimulates insulin secretion by pancreas
glucose-dependent insulinotropic peptide (duodenum and jejunum)
what are the three phases of GI control
- cephalic (head)
- gastric (stomach)
- intestinal (small intestine)
hormone released from adipose cells when calories exceed demands, suppresses hunger and increases metabolism
leptin
named after a related gene controlling hair color in rodents. powerful antagonist of MC3R and MC4R melanocortin receptors in the hypothalamus
agouti-related protein (AGRP) - obese people have elvated levels
produced in hypothalamic neurons and other neurons of the sympathetic nervous system. stimulates appetite via several receptors
neuropeptide Y (NPY)
neuropeptide precursor protein that is abundant in hypothalamus, unregulated after cocaine or amphetamine administration
cocaine and amphetamine regulated transcript (CART)
reduce food intake when injected into the third cerebral ventricle
CART derived peptides
precursor protein for melanocyte stimulating hormone (MSH), release of ___ product, beta-endorphin, is regulated by NPY
pro-opiomelanocortin (POMC)
effective peptide that binds to receptors on neurons and other tissues. inhibits food intake and fat deposition
alpha-melanocyte stimulating hormone (alpha-MSH)
what are two satiety factors
insulin and CCK
what are two orexigenic factors (appetite stimulating)
ghrelin and resistin
____ cells produce hydrochloric acid
parietal
net result of acid production
- H and Cl are secreted into the lumen of stomach
2. bicarbonate enters the interstitial fluid and then blood
what three factors secrete acid
- PNS
- gastrin
- histamine (paracrine)
____ stimulates gastrin secretion
PNS
increased acidity ___ gastrin release
inhibits
effects of food entry into duodenum
+ = osmolarity, fat and acid, distention
small volume of primary secretion contains water, electrolytes, and digestive enzymes
acinar cells
large volume cells, bicarbonate rich secretion
duct cells
hormones secreted by duodenum in response to the partially digested output from the stomach, which is called chyme
CCK cholecystokinin
CCK stimulates ___ cells to secrete enzymes
acinar
secretin stimulates ___ cells to secrete bicarbonate
duct
stimuli for CCK release
fat and amino acids in duodenum
stimuli for secretin release
acidity in duodenum
stimulates bile secretion from liver
secretin
stimulates gallbladder contraction and relaxation of sphincter of oddi
CCK
name three incretins
- glucagon like peptide - 1
- oxyntomodulin (OXM)
- glucose-dependent insulinotropic peptide (GIP)
secreted from L cells of the ileum and colon, hormone/neurotransmitter has half life of only 1-2 minutes, has receptors in the brain. stimulates insulin secretion by beta-cells
glucagon like peptide - 1
secreted from L cells, hormones appears to exert its effect through receptors for GLP - 1 as well as OXM specific receptors
oxyntomodulin (OXM)
secreted from k cells, hormone inhibits gastric motility and stimulates insulin secretion
glucose-dependent insulinotropic peptide (GIP)
important pair of neurotransmitters are derived from a common precursor together with their G-protein linked receptors OX1-R and OX2-R. arousal from sleep and food seeking behavior
orexins A and B (hypocretins)
accounts for migrating motility complex, “housekeeping contractions”, stimulates upper GI motility
motilin
found in gastric/duodenal mucosa and pancreas, stimulated by acid, inhibited by Ach, inhibits the release of all gut hormones
somatostatin
gastrin and Ach cause release from cells in stomach, stimulates acid secretion
histamine
