GI Overview Flashcards
salivary gland are controlled by SNS or PNS
PNS
what do salivary glands respond to for PNS
Ach & Substance P
water mucus saliva has high amounts of
HCO3- & K+, α-amylase, lingual lipase, mucin secreted
where are touch receptors for gag reflex
pharynx
what nerve resopnds for gag reflex
vagus
describe the vomiting reflex
Expulsion of upper intestinal & gastric contents by reverse peristalsis (Irritation of pharynx via vagal & sympathetic afferents to vomiting center)
what nerves respond for swallowing reflex
cranial nerves including vagus
in body and fundus what does stomach secrete
HCl, IF, Pepsinogen, mucus
in Antrum of stomach what does it secrete
gastrin
what nerve is responsible for the churning of stomach
vagus
what kind of paristalsis for stomach
antral peristalsis
what two agents are used to digest food
hydrochloric acid and pepsin
what is the name for the vigorous mixing of the stomach
antral peristalsis
what secretes intrinsic factor
stomach
intrisic factor is needed for
vitamin B12 absorption
describe receptive relaxation
Fundus/body relax to receive food, water or gas (vagovagal reflex - Vagal release of VIP)
what nerve is responsible for receptive relaxation
vagus
describe the gastrocolic reflex
Mass movements in colon after meal enters stomach (PNS, CCK, gastrin)
describe Gastroileal reflex
Increased segmentation in ileum in response to a meal in the stomach and/or gastric emptying (PNS, CCK, gastrin
describe Ileogastric reflex
– Chyme in ileum decreases gastric emptying (ENS, autonomic nerves)
describe vomitting reflex
Expulsion of upper intestinal & gastric contents by reverse peristalsis (Irritation of stomach via vagal & sympathetic afferents to vomiting center)
the SI absorbs what
carbs
proteins
lipids
what does duodenum secrete
bicarbonate
why does duodenum secrete bicarbonate
to neutralize the stomach acid
in comparing duodenum, jejunum, and ileum, describe the levels of absorption
highest absorption in duodenum, then jejunum, then ileum
describe the Enteroenteric (intestinointestinal) reflex
One area of small intestine overdistended, the rest of the SI will relax, causing cessation of motility (Enteric and autonomic nerves (sympathetic)
exocrine pancreas secretes what
HCO3- and enzymatic component
what is function of pancreas excreting HCO3-
to neutralize the acid from stomach
what is function of pancreas secreting enzymatic component
digest carbohydrates, proteins, and lipids into absorbable molecules.
liver and gall bladder secrete
bile salts
what is function of bile salts
solubilize fats and fat-soluble vitamins and allow these digestion products to be absorbed by enterocytes
what does large intestine absorb
water and salt
how does large intestine mix the
Haustra contractions
what is bacteria’s role in large intestine
helps breakdown undigested CHOs and proteins
describe Colonocolonic reflex
Distension of one area of colon will relax other areas of colon (ENS & sympathetic nerves)
describe Gastrocolic reflex
The motility of proximal and distal colon and the frequency of mass movements increase after a meal enters the stomach. (Mediated by CCK and gastrin)
what does CHO stand for
carbohydrate
describe the Rectosphincteric (defecation) reflex
feces entering rectum causes peristalsis & relax the internal anal sphincter (ENS & PNS)
point to submucosal plexus and myenteric plexus in GI tract
pg 13
what is the name of the intrinsic regulation of the GI system
enteric nervous system
where is enteric nervous system contained
submucosal and myenteric plexuses in the wall of the GI tract
what are the extrinsic components of GI tract
PNS and SNS
what is another name for myenteric plexus
(Auerbach’s plexus
where is myenteric plexus
between the outer longitudinal and middle circular muscle layers
what is another name for submucosous plexus
Meissner’s plexu
where is Submucous plexus located
between the middle circular layer and the mucosa
what does the enteric nervous system control
contractile, secretory, and endocrine functions of the GI tract.
what kind of muscle is in the proximal and distal ends of GI tract
skeletal muscle
most of the GI tract has what kind of muscle
smooth
parasympathetic innervation of GI tract is mainly
vagus and pelvic nerves
what part of nerves for PNS interacts with GI
preganglionic
the preganglionic nerves of PNS often synapse with wht in GI tract
enteric nervous system
what part of sympathetic nervous system joins GI
postganglion
what monitor distension and contraction
Mechanoreceptors or stretch receptors
what monitors the composition of intestinal contents
chemoreceptors
mechanoreceptors and chemoreceptors relay info to the CNS via what nerve
vagus
when mechanoreceptors and chemoreceptors relay info to CNS via vagus nerve, and reflex is triggered, how does that signal travel
efferent vagus
what is a vagovagal reflexes
both afferent and efferent limbs are in the vagus nerve
what percentage of secretions is absorbed
99%
1% is excreted
what is the cephalic phase
start getting salivary secretions. like when you start thinking about eating. PNS
if food irritates pharynx what happens
reverse peristalsis: vomiting reflex.
where is the lowest part the vomitting reflex can take place
upper SI
why is there secondary peristaltic wave
sensory afferents going to CNS telling that there is something stuck in lower 2/3 of esophagus
what does primary peristaltic wave do
move food into stomach
what plexus stimulated for secondary peristaltic wave
aurbauch’s plexus
when stomach recives food what needs to happen to fundus
needs to relax
receptive relaxation
vagovagal reflex
once food is received in stomach, what chemicals are released
HCl
IF
Pepsinogen
Mucus
what does HCl do
breaks food down
lowers pH
pepsinogen only activated if there is
acidic pH
IF stands for
intrinsic factor
what is function of IF
absorption of Vitamin B12
where is IF being released
parietal cells
parietal cells release what
IF and HCl
gastrin is important hormone it is released
from G cells in antrum of stomach
gastrin is important in
motility patterns
stimulates parietal cells to secrete acid
gastrin is a
hormone
gastrin stimualtes parietal cells to
produce acid
antral peristalsis, what is it
non-propuslive churning and mixing in stomach
gastrocolic reflex
meal is in stomach, starts to empty into SI, colin increasing mass movement of previous meal, trying to clear out previous meal
increase in motility in colon to prepare for next meal being processed in stomach
gastroileal reflex
in response to gastric emptying, ileum increases segmentation contraction
tells stomach to slow down if Si isn’t done
where is major digestion absorption
SI
why does SI have major absorption?
has transport proteins on apical and basolateral side
why is there a lot of electrolyte absorption in upper part of SI
osmotic gradient
the cells are much more leaky here
a lot of transport molecules that use sodium
if your pancreas doesn’t function you’ll have
malnutrition
what is main function of large intestine
finish off absorption of salt and water
what are the 2 motility patterns in large intetine
haustra
transit motility
haustra is basically the same as
segmented, they just callit haustra b/c it clamps down on intestine
draw out layers of muscle layers/plexus
pg 14
describe the transcellular path of absorption
substance has to cross the apical membrane, enter inttestinal epithelial cell, and be extruded from cell across basolateral membrane into blood
describe the paracellular of absorption
substances move across the tight junctions between intestinal epithelial cells, through the lateral intercellular spaces, and into the blood.
label the intestinal folds describing their folding
pg 20
what does UES stand for
upper esophageal sphincter
what does LES stand for
lower esophageal sphincter
what does the sphincter of oddi do
controls flow of bile from common bile duct
draw out the sphincters of GI
pg 22
what is function of somatostatin
inhibits secretion of all GI hormones
hormones are released from what cell in GI tract
endocrine cells
name the five GI peptides classified as hormones
gastrin, cholecystokinin (CCK), secretin, gastric inhibitory peptide (GIP or glucosedependent insulinotropic peptide), and motilin.
what does CCK stand for
cholecystokinin
hormones are secreted into
portal circulation
hormones are secreted into portal circulation and then enter
systemic circulation
systemic circulation does what for hormone
delivers hormone to target cell with receptors for that hormone
what are neurocrines
peptides synthesized in neurons of GI tract and released following AP
when are neurocrines released
after AP
name 7 neurocrines
ACh, norepinephrine, vasoactive intestinal peptide (VIP), gastrin-releasing peptide (GRP), enkephalins, neuropeptide Y, and substance P.
what does VIP stand for
vasoactive intestinal peptide
what does GRP stand for
gastrin-releasing peptide
paracrines are secreted by what cells
endocrine cells of GI tract
what is difference b/w paracrines and hormones
paracrines act locally w/in the same tissue that secretes them
name two paracrines
somatostatin
histamine
where is amylase secreted
pancreas & saliva
where is pepsin secreted
stomach
in order to absorb carbohydrates have to get to
monosaccharide level
trypsinogen is the
proenzyme for trypsin
what enzyme stimulates colipase to be active
trypsin
trypsin acts on all
proenzymes to stimulate their activation
what motility pattern predominantes
peristalsis
rhythmic segmentation predominates during
fed state
tonic contraction happens where?
sphincter
tonic contraction allows for
different parts of GI tract to be separated
in response to chyme going into duodenum,
gall bladder contracts
when gall bladder contracts what happens to sphincter of oddi
relaxes
gastrin main effect
secreted from G cells in stomach
goes to parietal cells in stomach and stimulates acid secretion
CCK main effect
stimulates pancreatic acinar cells to secrete digestive enzymes
contracts gall bladder
relaxes sphincter of oddi
inhibits gastric emptying
secretins main effect
released from mast cells in intestine
go to ductal epithelial cells in pancreas, make them release bicarb
GIP main effect
acid secretion
intrinsic factor release
motilin main effect
elevated during fasting state
somatostatin main effect
inhibits almost all GI peptides
histamine main effect
increases acid secretion
