Flashcards in Neural/Hormonal control of GI Deck (80):
3 main ways GI prevents invasion of pathogens
largest immune system
microbiota of gut can be influenced by:
2 main goals of intestinal smooth muscle contractions:
How to prevent dehydration in digestion?
reabsorption from lumen
Really bad antibiotic induced diarrhoea can be treated how?
What are the local GI pace-maker cells?
interstitial cells of Cajal
What is GI endocrine system used to communicate with?
intestinal mucosa to brain/pancreas/gall bladder for appetite and secretion
What kind of nerves does the ENS have?
Where does the submucosal plexus lie? what does it control?
between submucosa and mucosa
control water and electrolyte secretion
What does ICC stand for?
interstitial cells of Cajal
95% of seretonin is made where?
within gut mucosa
what cells in the GI release histamine?
enterochromaffin cell-like cells
what are EE cells? what do they contain?
CCK, secretin, somatostatin, glucagon peptides
which cells release serotonin in the GI?
Vago-Vagal reflex does what?
coordinate movement in upper GI
stomach secretion and movement
What is the intestino-intestinal reflex mediated by 3 things:
dorsal root ganglia/spinal cord
Does CNS have any influence on GI?
Yes, anticipation of food (cephalic phase of digestion)
mood such as fear and butterflies in stomach.
GI hormones excite what before entering the blood stream? how?
excite enteric and extrinsic sensory neurons via paracrine action
what modulates enteric neural circuits? 2 things
Can the ICCs be modified?
Yes like the SA and AV nodes, neurons can adjust levels of excitation/inhibition
Appearance of food matter? example?
yes, changes how we experience it
red lollies are sweeter than green ones even with same amount of sugar in them
How does the cephalic phase of digestion operate via?
vagus nerve only
What does the cephalic phase of digestion do to the stomach?
gastric acid/pepsin secretion
relaxation of gastric corpus/fundus
acid secretion comes from which cells?
What 4 mediators help regulate stomach acid secretion?
ACh from ENS via vagus
Gastrin from G-cells
Histamine from ECL cells
Where are G cells located predominantly?
antrum and duodenum
What does somatostatin do?
inhibit parietal and G cells
Where does somatostatin comes from? how stimulated?
D-cells stimulated by acid/gastrin in duodenum
what is Histamine in ECL cells inhibited by?
somatostatin from local D cells
peristalsis is controlled by which nerve?
entirely by vagus
If CNS is not working, can you get peristalsis?
yes ENS can activate secondary peristalsis
Lower oesophageal open or closed normally?
normally closed or else GORD
Stomach can distend how much?
3-4 times it's size
What does stomach distension activate? 3 things
increased acid secretion
What propels food from corpus to antrum to pylorus?
ICC (pacemaker cells)
what happens to fat in the stomach?
separates out to fundus so it's last to come out
what is gastroparesis?
inability for pylorus to open effectively, life threatening for diabetics
what is the order food coming out of stomach?
carbs>proteins>fat at end
failure to neutralize acid in duodenum causes what?
after acid in duodenum, D-cells do what?
release somatostatin to decrease parietal activity
What does Brunner's Glands release?
mucus and bicarbonate
How are Brunner's glands activated?
via vagal afferents: vago-vagal reflex
two things inhibit gastric emptying once acid is detected in the duodenum, they are?
I cells secrete what?
What does CCK do?2 things?
helps with vagovagal reflex
where does secretin come from? what does it release?
initiates bicarb secretions from pancreas
neutralizing acid in duodenum inactivates two things:
somatostatin from D-cells
how do you uninhibit gastric emptying?
once secretin is released it terminated acid stimulated inhibition of gastric emptying
what is retropulsion?
used by duodenum to push pancreatic juices up towards pyloris to get better mixing and neutralize pH
CCK as a hormone causes what 3 main effects
gall bladder contractions
release enzymes from pancreas
satiety factor on hypothalamus
2 ways CCK suppresses appetite:
directly on hypothalamus
can intestinal mucosa sense food texture?
yes, larger chunks of food detected will slow down propulsion
EC and EE cells are not mechanosensitive?
False. some of the are
What does fat and protein do to appetite in lean and obese people?
obese: won't respond
Enterochromaffin cells 'taste'?
Yes, everything from bitter to umami and capsaicin
EC cells release what after tastant activation?
what cells express components of sweet taste receptors?
glucose or artificial sweeteners activates what?
tips of villi and will absorb more carbs.
what is PYY?
pancreatic polypeptide Y
Where is PYY found? what is it for?
in L-cells for appetite and insulin secretion
once you pass duodenum which neural system takes over?
from vagus to enteric
3 motor patterns are activated once food is in duodenum:
segmentation: local constrict/relax
Which is slower? segmentation or peristalsis?
what determines efficacy of digestion and absorption?
rate of transit
Fat emptying from stomach last does what?
surge of CCK to feel really full
what makes contents more viscous as you pass from jejunum to colon?
absorption of water
what happens in proximal colon?
fermentation by microbiome to create short chain fatty acids
What is Hirschsprung's disease?
babies without ENS
what triggers urge to defaecate?
distension of rectum via sacral primary afferent neurons
irritable bowel syndrome causes what to rectum?
reduced threshold and can detect faeces in rectum
What moves faecal matter from colon to rectum?
do you need conscious activity to relax anal sphincter?
yes for normal defecation
what is MMC?
migrating motor complex
What does MMC do?
wave of constriction in antrum propagating to ileocolonic junction
How many MMCs in the small intestine at once?
MMC does what to bacteria?
clears bacteria and cellular debris from an empty lumen?
When does MMC occur?
in the fasted state
how is MMC regulated?
what does Ghrelin do? when released?
during fasted state