Flashcards in Physio Deck (23):
What are the 4 GI peptide hormones?
gastrin, secretin, CCK, glucose-dependent-inhibitory peptide (GIP)
-secreted by G cells of tummy (antrum)
-stomach distention/vagal stimulation via GRP (gastrin releasing peptide) cause secretion
-increase gastric H+ secretion (directly on parietal cell for HCl and indirectly ECL cell for HA)
-secreted by I cells of duodenum/jejunum
-secreted in response to fats
-increase gallbladder contraction, pancreatic enzyme/bicarbonate secretion
-decreases gastric emptying
-secreted by S cells of duodenum
-secreted when chyme leaves tummy
-increases bicarb/pancreatic fluid sectretion
-inhibits gastrin (therefore, stops acidic secretions), stops gastric emptying
glucose-dependent insulinomic peptide (GIP)
-secreted by K cells of duodenum/jejunum
-secreted in response to fat/carbs
-stimulates insulin secretion from pancreas
-inhibits HCl secretion by parietal cells
What does VIP do?
-neurocrine of mucosa/smooth muscle
-relaxes smooth muscle
-increases intestinal secretions
-increases pancreatic secretions
What are the GI paracrines?
somatostatin, serotonin, histamine
-enterochromaffic cells of intestine
-respond to distension by exciting ENS to increase motility and secretions
-D cells of tummy produce it
-inhibits pancreatic and gastric secretions, motility
-can be endocrine or paracrine
-released by EC-like cells in tummy
-stimulates HCL secretion (H2 receptors)
mucus neck cells, cardiac glands (these only near esophagus)
-secrete mainly mucus
-in antrum of tummy
peptic (chief) cells
-secrete pepsinogen (cleaved to pepsin at low pH) and gastric lipase
-in body of tummy
parietal (oxyntic, acid-forming) cells
-secrete intrinsic factor (cyanocobalamin reab. in ileum) and HCl
-in body of tummy
HCO3-/Cl- exchanger (no energy!!)
bicarb from carbonic anhydrase sent to blood, Cl- enters from blood
H+ from carbonic anhydrase into tummy lumen (digestion), K+ into cell
What does prolonged vomiting cause?
hypokalemia (kidney response), alkalosis (lost HCl), dehydration (lost volume/H2O)
What stimulates acid secretion?
histamine, vagus, gastrin, caffeine, insulin, stress
What inhibits acid secretion?
somatostatin, GIP (gastric inhibitory peptide), secretin, glucose insulinotropic peptide
Whom does the vagus stimulate?
-parietal cells, ECL cells, D cells (directly via ACh)
-G cells (via GRP)
-D cells (inhibits somatostatin via ACh)
What's in saliva normally?
-hypotonic (less osmolarity than plasma)
-alpha-amylase, lingual lipase
-high K+, high bicarb
-low Na+, low Cl-
-uses Cl-/bicarb, K+/H+, Na+/H+ transporters
What about high flow rates?
-less time for ion reabsorption
-bicarb higher, K+ low
-saliva more like plasma
What about low flow rates?
-more time for ion reabsorption
-more K+, lower bicarb