Exam 2: GI Tract Flashcards
Largest and most complex endocrine organ
GI tract
Percentage of cells of GI tract that secrete hormones
1%
Enteroendocrine cells interact extensively w/
ANS and ENS
GI tract is a ___ organ
Sensory
Gut NT
Catecholamines
ACh
Peptides
Peptides from neutrons and gut can act as
NT
Neurohormones
Neuromodulators
Vagus supplies para innervation to
Esophagus
Stomach
SI
Prox colon
Remainder of colon and rectum receive para supply from
Pelvic N from sacral cord levels
Hormonal stim of vagal afferents communicate w/ ____ w/out having to cross
Brain stem; BBB
2 forms of gastrin
Little — response to eating
Big — low levels btw meals
Gastrin is secreted by
G cells in antrum of stomach
Functions of gastrin
Promote H+ secretion — lowers pH — activates pepsinogen
Starts protein digestion
Stimuli of gastrin secretion
Products of protein digestion
Distention of stomach
Stim of vagus
Gastrin is inhibited by
Somatostatin
Low stomach pH
Excess gastrin causes
Inc H+ ion secretion
Hypertrophy of gastric mucosa
Deficiency of gastrin
Dec H+ secretion
Atrophy of gastric mucosa
Zollinger-Ellison syndrome
Gastrin secretion tumor “gastrinoma”
Gastrinoma frequently found in
Pancreas
Gastrinoma causes
Inc H+ secretion
Hypertrophy of stomach mucosa
Duodenal ulcers
Acidification of intestinal lumen
Treatment of Zollinger-Ellison syndrome
H2 receptor blockers
H+ pump inhibitors
Remove tumor
CCK coordinates and promotes
Fat digestion and absorption
CCK has some
Gastrin activity
CCK secreted by
I cells of duodenal and jejunal mucosa
CCK secreted in response to
MG and FA (NOT TGs)
Small peptides and AA
A meal containing ______ will stim release of CCK
Fat and protein
5 major actions of CCK
- Contract gallbladder
- Secrete pancreatic enzymes
- Secrete HCO3 from pancreas
- Tropic effect on pancreas and gall
- Inhibit gastric emptying
Purpose of CCK contracting gallbladder
Ejects bile into lumen of SI
Bile emulsifies and solubilizes dietary lipids
Pancreatic enzymes secreted in response to CCK
Lipases
Proteases
Amylase
Purpose of inhibiting gastric emptying
Enhances fat digestion/absorption
Secretin 50% homologous to
Glucagon
Tertiary structure of secretin
Alpha helix
Secretin is secreted by ___ in response to
S cells in duodenum; H+ and FA in SI
Secretin promotes
Secretion of pancreatic and biliary HCO3
Purpose of HCO3 secretion
Neutralize H+ in lumen of SI
Essential for fat digestion
Secretin inhibits effects of
Gastrin
GIP is secreted by
K cells in duodenal/jejunal mucosa
Major effect of GIP
Stim of insulin
GIP inhibits
Gastric H+ secretion (animals)
GIP secreted in response to
All 3 types of nutrients
Motilin is secreted from
Upper duodenum during fasting
Motilin is responsible for
Migrating motility complex
Motilin stimulates
Enzyme secretion by stomach and pancreas
Contraction of gallbladder
GLP secreted by
L cells in intestinal mucosa
GLP effects on liver
Inc glycogenolysis and GNG
GLP-1 inhibits
Glucagon secretion Food intake Patietal cells (dec H+)
GLP-1 stimulates
Insulin secretion
D cells — secrete somatostatin
GLP-1 slows
Gastric emptying
GLP-2 trophic effect on
Intestinal mucosa — proliferation — inc surface area for absorption
GLP-2 has no effects on
Insulin secretion
GLP-2 decreases
Inflamm responses to bowel injury
Ileal brake mechanism
Slow gastric/pancreas secretion, stomach emptying and intestinal motility
GLP-1 and peptide YY feeds back on stomach in order to
Inc nutrient absorption
Paracrine hormones in GI tract
Somatostatin
Histamine
Histamine works synergistically with
Gastrin and ACh to stimulate H+ secretion
ACh neurocrine actions
Contract smooth ms
Inc saliva
Inc gastric secretion
Inc pancreatic secretion
NE neurocrine actions
Relax smooth ms
Contract sphincters
Inc saliva
VIP neurocrine actions
Relax smooth ms
Inc intestinal secretion
Inc pancreatic secretion
GRP neurocrine action
Inc gastrin secretion
Enkephalins neurocrine actions
Contract smooth ms
Dec intestinal secretion
Neuropeptide Y neurocrine actions
Relax smooth ms
Dec intestinal secretion
Substance P neurocrine actions
Contract smooth ms
Inc salivary secretion
Para neurocrines
ACh VIP GRP Enkephalins Substance P
Sym neurocrines
NE
Enkephalins
Neuropeptide Y