The Basics Flashcards
Submucosal plexus controls and is located in
secretions, circulation, muscularis mucosae contraction
mixing motion of contraction
submucosa
enteric NS is made of what 2 plexuses?
Submucosal
myenteric
myenteric plexus is located where and controls what
between muscle layers
controls motility
Ach
increases activity of enteric NS
also used by ANS
VIP
increases secretion
decreases motility
vasodilates
Norepi
decreases avtivity, especially motilit
also used by extrinsic ANS
NItric oxide
major inhibitory NT of enteric
required to cause relaxation
DZ ass’d with NO
Hirschbrungs= restriction tightly contracted. obstruction Aclasia= LES doesnt relax, swallowing painful. AI prolem
Endorphins action
action to decrease peristalsis
increase mixing motions
net effect= slow down and absorb more H20
when given opiods for pain releif, constipation is a frequent occurence
Sympathetic effects in GI
Sympathetic has effects on enteric decreases activity of intrinisc neurons decreases GI functions Decreases BF (which will cause a decrease in secretions) decrease motility increases sphincter tone
Parasympathetic effects on GI
increase activity of intrinisc neurons increase most GI functions increase BF increase secretion increase motility relaxation of sphincters
Local reflexes in the gut
distension in stomach increases gastric motility clear out the distention moves stuff on into the small intestine neurons located entirely in enteric NS no involvement of CNS or ANS
Long loop reflexes
distention in stomach
relaxation in colon
“get ready here comes food”
afferent to sympathetic ganglia, then back to gut.
something in one area of GI causes an effect that will be somewhere else in the GI. via sympathetic chain
Longest reflexes in GI
cell body in dorsal root ganglinon (not enteric) to CNS back to gut ie= response to pain. created when another sytem gets involved
Gastrin - function
increases motility
increases acid secretion
increases pancreatic enzyme secretion
Gastrin - released by
G cells in pyloric glands in response to distension
Secretin - released by
S cells of intestine, in response to acid in the duodenum
Secretin - function
MAIN FXN= protection against acid
stomach - decrease gastrin, decrease acid, decrease motility, increase enzymes
pancreas - increase bicarb, increase enzyme
liver - increase bicarb
CCK-PZ - released from
I cells of intestine, in response to fats in duodenum
CCK-PZ - function
MAIN ROLE - increase enzyme secretion from pancreas, deal w/fats
pancreas - increase enzyme secretion (pancreozymin)
Gall bladder - contraction of the gallbladder, relax sphincter of oddi
Brain, liver - satiety
GLP-1 - released from
L cells, in response to nutrieents, particularly fats and fiber in the intestine
GLP-1 - function
Pancreas - increase insulin secretion
stomach - decrease gastric acid, decrease motility
these are activated later in the intestine
GLP - 2 - released from
L cells of intestine
in response to nutrients, primarily fats and dietary fiber,
ALSO INTESTINAL INJURY
GLP-2 - function
trophic factor for intestine
growth of villi, mucosal, hyperplasia
Motilin - released from
stomach, SI, colon
stimulus unknown.
increases every 100 minutes btwn meals
Motilin function
excitatory to GI motility, particulary the occurence of the
MIGRATING MOTOR COMPLEX
ANS control of GI BF
sympathetic - vasoconstriction, may totally occlude
parasympathetic - dilation
Describe counter current BF in villus
due to the counter current of BF, O2 from artery diffuses across to venous blood down concentration gradient,
the tip of the villus is hypoxic ALL the time
bc of hypoxia, cells at tip of villus have a short life span and are routinely shed from villus into lumen
P glycoprotein - What is it?
MDR-1 gene product
multi drug resistant
protein survived drug doses that were fatal to other cells
P-glycoprotein - What does it do?
remove drugs/ other exogenous substances from cell lumen (prevent absorption). substrate comes into cell, and Pglycoprotein sees it and kicks it back out into the lumen.
Think about this when given drugs, taking in new things.
if given 50mg penicilin orally, might only take in 10 mg.
P-glycoprotein - Why study?
influence on drug absorption and therefore effect on efficacy of drug. less p-glycoprotein expression –> more drugs in plasma and vice versa.
polymophisms also suggested in susceptibility to inflammatory bowel dz and colon cancer.
possible that toxins made by intestinal flora are normally extruded from intestinal cells by p-glycoproteiin. in humans, a region on chromosome 7 has been linked to susceptibiltity to IBD and colon cancer.
