Lecture 8- Gastrointestinal Flashcards
3 components that regulate the GI tract
neurons
paracrine mediators
hormones
neurons that regulate the GI tract are from the … and … nervous systems
autonomic
enteric
paracrine mediators are produced by …. and reach target cells via …
local cells
diffusion
hormones are produced by … cells and reach gut via…
endocrine
blood
3 types of neurons involved
motor
interneurons
sensory
3 receptors of the GI system
mechano-
osmo-
chemo-
the receptors of the GI tract (mechano, osmo and chemo) are initiated by …. (4)
distension of the wall
chyme osmolarity
chyme acidity
chyme concentrations
what are the 4 main hormones that play a large role in regulating digestion
gastrin
cholecystokinin (CCK)
secretin
glucose-dependent insulinotropic peptide (GIP)
3 generalizations of GI hormones
- Each hormone participates a in feedback control system to regulate some aspect of the GI lumen
- Each hormone affects more than one type of target cell
- Hormones can have synergistic effects
3 phases of GI control
cephalic
gastric
intestinal
the cephalic phase involves …. nerve fibers affecting the … and they are initiated when receptors in brain are stimulated
parasympathetic
ENS
the gastric phase is involved in … and … neural reflexes and involves the hormone …
short
long
gastrin
the gastric phase occurs during 4 different scenarios
distension
acidity
amino acid breakdown
peptide breakdown
the intestinal phase is involved in .. and … reflexes and involves the hormones … , … and …
short long CCK GIP secretin
the intestinal phase occurs during 4 different scenarios
distension
acidity
osmolarity
various digestive products
where is the majority of bacteria killed in the GI system
stomach
there are … sections of the stomach and … glandular regions
3
2
the 3 sections of the stomach are
fundus
body
antrum
the body of the stomach secretes … , … and …
mucus
pepsinogen
HCl
the antrum of the stomach secretes … , … and …
mucus
pepsinogen
gastrin
what are the 2 glandular regions of the stomach ?
oxyntic (top)
pyloric (bottom)
parietal cells produce … and … in the fundus and body of the stomach (oxyntic gland area)
HCl
intrinsic factor
chief cells produce … in the body and antrum of the stomach (oxyntic and pyloric gland area)
pepsinogen
mucous is secreted by … cells throughout all sections of the stomach
mucous neck cells
HCO3 is secreted by … throughout all sections of the stomach
epithelial cells
Gastrin is secreted by … cells in the ….
G
antrum (pyloric gland area)
Somatostatin is produced by …. cells throughout the stomach at the base of the …. glands
D
gastric
histamine is secreted by ….-like cells
enterochromaffin
… is responsible for the production of HCl
carbonic anhydrase
… is the strongest HCl stimulant
histamine
histamine release can be triggered by … or …
gastrin
Ach
… and … can have direct effects on parietal cells
gastrin and Ach
in all cases of input to parietal cells, activation of receptors results in … activation that increases the ability of parietal cell s to release H+ and Cl-
second messenger
… is a potent inhibitor of HCl secretion
somatostatin
somatostatin has 2 mechanisms in which it can inhibit HCl secretion from the parietal cell
- G cell
- D cell
the cephalic phase is triggered through ….. of food and activates the … and production of …
(also mechanical stimulation from chewing and swallowing)
sigh, smell, taste of food
PNS
Ach
the gastric phase is triggered by …, presence of proteins, peptides and amino acids. this increases…. secretion
distension
gastrin
the intestinal phase initially enhances … secretion but later in digestion, the intestinal phase is ….
HCl
inhibitory
in the intestinal phase, when the pH of chyme is less than 3, … is produced
secretin
in the intestinal phase, high H+, amino acids, and fatty acids stimulate …. which …. HCl production
CCK
decreases
what 2 things prevent HCl and pepsin from degrading gastric tissue
mucus
HCO3- production from gastric epithelial cells
pepsinogen is produced by … cells and … helps to cleave it to pepsin
chief
HCl
pepsinogen is a … meaning it is a proenzyme that needs to be cleaved to become active
zymogen
… is a hormone produced by intestinal cells that inhibit the secretion or motility in the stomach.
enterogastrone
secretin and CCK too
the pancreas is an … gland and it produces … and …
bicarb ions
digestive enzymes
pancreas is important in the secretion of …
trypsinogen
… converts trypsinogen to trypsin
enteropeptidase
CCK secretion is potentiated by …
secretin
an increase in intestinal fatty acids and amino acids will cause an increase in … secretion in the small intestine, leading to increased … in plasma, leading to increase enzyme secretion in the pancreas leading to increased flow of enzymes into the SI and increased digestion of fats and proteins–> absorption
CCK
CCK
CCK strongly potentiates the effects of …
secretin
the … produces bile and secretes it into small ducts called …. which converge and drain into larger bile ducts
liver
bile canaliculi
the liver synthesizes about …. of bile salts a day
but, …. of bile salts are secreted a day
20-60 mg
1200-3600 mg
more bile salts are secreted than synthesized because they are … though the enterohepatic circulation
recycled
increased CCK will cause the gall bladder to …. to increase bile flow into the common bile duct and it will also cause …. of the sphincter of Oddi to increase bile flow into duodenum
contract
relaxation
2 types of smooth muscle contractions in the small intestine
peristalsis
segmentation
… is described as progressive contractions of successive sections of circular smooth muscle
peristalsis
… is described as closely spaced contractions of the circular muscle layer. when this is rhythmic (contract/relax) chyme is mixed and slowly moved downward
segmentation
during absorption, … contractions occur
segmentation
after most absorption has occured, … contractions occur
peristaltic
peristalsis is driven by a migrating …
myoelectric complex
the myoelectric complex starts in lower …. and travels about 2 feet prior to dying out. it is initiated by the intestinal hormone …
stomach
motilin
food bolue enters the large intestine through the … valve
ileocecal
primary purpose of the large intestine is to actively transport … from lumen to blood. also, … secretion is coupled to … absorption
Na+
HCO3
Cl
…. of some food bolus contents maximizes the absorption of nutrients from the food
bacterial fermentation
motility in the large intestine occurs as slow … contractions and ….-like contractions occur 3-4 times per day
segmentation
peristaltic