endocrine control of digestion - lecture Flashcards
insulin shock
if too much insulin
get hyperglycemia
fuzzy headed, forgetful, pass out, can go into coma and die
give epinephrine (substance E)
functions of GI system
filling and emptying of GI tract must be coordinated with smooth muscle motility, the secretion of digestive agents, absorption of nutrients and elimination of waste products
coordinated functions under the control of neuronal, endocrine, and paracrine signaling mechanisms
oral cavity functions
lubrication, mastication, discrimination, air-lock portal
functions of stomach
decontamination of food, mainly with acid
pepsin also breaks down bacterial cell walls
in antrum, grind up food
functions of small intestine (duodenum)
digestion and absorption of food
neutralization of acid from stomach in duodenum
bile excreted to here
epithelial cells secrete and absorb materials
ilium only area that can take up vitamin B12 and take up bile again
functions of large intestine
bacteria that breaks down food
absorption of water and salts
innervation of GI tract
both intrinsic and extrinsic autonomic nervous system
secretion and actions of gut hormones intimately associated with ANS innervation of the GI tract
peptide hormones
secreted into blood by endocrine cells scattered along the GI tract
act both at level of digestive organs and the CNS
parasympathetic innervation of digestion
via cholinergic pathways
activates digestion
from vagus nerve
sympathetic innervation of digestion
adrenergic
to three ganglia
then postganlionic fibers that release norepi
enteric system
ANS 2 major networks/plexuses of nerves interconnect all portions of GI tract meissner's plexus is submucosal auerbach's plexus is myenteric
gastrin family of hormones
all have carboxylated c-terminal end
sulfonated Tyr 6th or 7th from carboxyl end
always have gly-trp-met-asp-phe-nh2
can use terminal 4 AA clinically as gastrin
important actions of gastrin
1: increases secretion of acid from oxyntic cells of the stomach (acts with histamine, Ach)
2: indirectly increases pepsinogen release from chief cells
3: trophic action on mucosa of the stomach - if make too much acid grow mucosal layer
4: stimulates gastric motility
gastrin levels after meal
peak within 20 minutes
things that stimulate gastrin release
peptide digestion products in the chyme
amino acids in the chyme (esp. tryp, phe, arg)
vagal activity through GRP/bombesin - released from nerve endings of vagal nerves
calcium in chyme
things that inhibit gastrin release
acid with pH below 3.5 = indirect effect through release of somatostatin through paracrine effect = negative feedback loop
important actions of CCK
1: stimulates pancreatic proenzyme/enzyme release
2: contracts the gall bladder, increasing the flow of bile
3: relaxes the sphincter of Oddi
4: reduces gastrin-induced acid secretion by competitive inhibition
5: important synergistic action with secretin on promoting release of pancreatic HCO3/H2O
factors that stimulate release of CCK
by I cells
peptides and AA (tryp and phe) in chyme - major control
fats and acidity (weak control)
secretin/glucagon family
need aminoterminal residue - knock that off and loses all bioactivity
important actions of secretin
1: stimulates pancreatic HCO3/H2O secretion into duodenum - synergistic with CCK
2: inhibits stomach acid secretion by inhibiting the release of gastrin
3: acts synergistically with CCK in promoting release of pancreatic enzymes, flow of bile, and composition of bile (increases HCO3/H2O content)
control of secretin release
released with introduction of acid into the upper small intestine (pH of less than 4)
S cells sense it an release secretin
secretion by region of stomach
in body, acid and pepsin from parietal cells and chief cells
in antrum, gastrin from G cells
in upper duodenal mucosa, secretin secreted from S cells
release of H+ from parietal cells
histamine, ACh, and gastrin potentiate the other two
synergism results in severe heartburn
peptic ulcer disease
if problem, Zollinger-Ellison syndrome - inject secretin to see if gastronoma
block histamine, block acid secretion
gastric phase
food goes in
both vagus and ingested food induce secretion of gastrin and H+
intestinal phase
secretin and CCK in concert with ACh provide buffering and enzymes during intestinal phase
gall bladder contracts in response to CCK and pour bile in duodenum
leptin
167 AA cytokine binds to Jak/Stat family of receptors secreted from adipocytes as a function of energy sufficiency and signals satiety to the hypothalamus creates feeling of satiety rise throughout day
ghrelin
28 AA peptide secreted from cells in stomach to blood in response to energy insufficiency acts centrally by increasing food intake acts through hypothalmic cells too also acts as GH releasing peptide goes up with meals
