endocrine control of digestion - lecture

Question 1

insulin shock

Answer 1

if too much insulin
get hyperglycemia
fuzzy headed, forgetful, pass out, can go into coma and die
give epinephrine (substance E)

Question 2

functions of GI system

Answer 2

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

Question 3

oral cavity functions

Answer 3

lubrication, mastication, discrimination, air-lock portal

Question 4

functions of stomach

Answer 4

decontamination of food, mainly with acid
pepsin also breaks down bacterial cell walls
in antrum, grind up food

Question 5

functions of small intestine (duodenum)

Answer 5

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

Question 6

functions of large intestine

Answer 6

bacteria that breaks down food

absorption of water and salts

Question 7

innervation of GI tract

Answer 7

both intrinsic and extrinsic autonomic nervous system

secretion and actions of gut hormones intimately associated with ANS innervation of the GI tract

Question 8

peptide hormones

Answer 8

secreted into blood by endocrine cells scattered along the GI tract
act both at level of digestive organs and the CNS

Question 9

parasympathetic innervation of digestion

Answer 9

via cholinergic pathways
activates digestion
from vagus nerve

Question 10

sympathetic innervation of digestion

Answer 10

adrenergic
to three ganglia
then postganlionic fibers that release norepi

Question 11

enteric system

Answer 11

ANS
2 major networks/plexuses of nerves
interconnect all portions of GI tract
meissner's plexus is submucosal
auerbach's plexus is myenteric

Question 12

gastrin family of hormones

Answer 12

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

Question 13

important actions of gastrin

Answer 13

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

Question 14

gastrin levels after meal

Answer 14

peak within 20 minutes

Question 15

things that stimulate gastrin release

Answer 15

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

Question 16

things that inhibit gastrin release

Answer 16

acid with pH below 3.5 = indirect effect through release of somatostatin through paracrine effect = negative feedback loop

Question 17

important actions of CCK

Answer 17

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

Question 18

factors that stimulate release of CCK

Answer 18

by I cells
peptides and AA (tryp and phe) in chyme - major control
fats and acidity (weak control)

Question 19

secretin/glucagon family

Answer 19

need aminoterminal residue - knock that off and loses all bioactivity

Question 20

important actions of secretin

Answer 20

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)

Question 21

control of secretin release

Answer 21

released with introduction of acid into the upper small intestine (pH of less than 4)
S cells sense it an release secretin

Question 22

secretion by region of stomach

Answer 22

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

Question 23

release of H+ from parietal cells

Answer 23

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

Question 24

gastric phase

Answer 24

food goes in

both vagus and ingested food induce secretion of gastrin and H+

Question 25

intestinal phase

Answer 25

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

Question 26

leptin

Answer 26

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

Question 27

ghrelin

Answer 27

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