15 Gut, ENS, Gastrointestinal Motility Flashcards
Nutrient Absorption chiefly occurs where?
small intestine (with less in the colon)
What % immune function of the body is in the gut?
60-70%
Gut Endocrine control includes what 4 substances?
- Gastrin from G cells
- CCK from I cells
- Secretin from S cells
- Motilin
Name the 4 non-peptide transmitters in the gut?
- ACh
- Histamine
- NO
- Norepinephrine
T/F the ENS (enteric nervous sys.) can function w/o the CNS?
T
ENS has how many neurons?
100 million (same # as spinal cord)
IPAN’s do what?
gut afferents to the MEDULLA (& reflex loops ex. vagovagoal), responding to chemicals, stretch, mechanical stimuli
Gut interneurons connect what?
IPANs w/ motor neurons
What 3 kinds of motor neurons are found in the gut?
- Muscle
- Secretomotor
- Vasodilator
Parasympathetics: vagus supplies the whole gut except what?
- Pharynx
- Distal third of colon (done by splanchnics)
Pharyngeal function is what CN’s?
5,9,10,12
T/F sympathetic nerves directly innervate gut cells?
T. (ALSO indirectly innervate via ENS neurons)
Gut CCK affects the brain how?
Induces satiety
Syncytium is what?
Layers of intestinal smooth muscle connected by gap junctions so that the whole layer activates simultaneously
T/F muscularis mucosa assists with motility?
F. Only helps w/ secretion & churning, not travel of food thru the bowel.
A chunk of food gets stuck in your intestine, causing stretch. What happens to the gut proximal and distal to this stretch?
- Proximal: Constricts
- Distal: Relaxes
Gut smooth muscle, once depolarized, constricts by what mechanism?
- voltage-dependent Ca channels &
- Release of internal Ca via G-protein cascade
What is gut slow-wave depolarization?
aboral (toward the anus) direction of depolarization. This is governed by ENS & has a dif. frequency in dif. parts of gut.
What are Interstitial Cells of Cajal?
Provide pacemaker activity for slow-wave gut depolarizations
Mixing/churning is don’t by what kind of contractions?
Segmental/phasic (not propagated downstream)
Food bolus proximal to a sphincter causes the sphincter to?
Open. (bolus distal to sphincter does the opposite)
Sphincters have what 2 functions?
- prevent retrograde flow
- provide reservoir function
Describe the phases of small bowel motility while fasting?
“Migrating Motor Complex (MMC)” phases:
1-quiescent
2-brief intermittent contractions, SOME of which propagate downstream
3-brief high-amplitude contractions that propagate downstream
Describe small bowel motility after feeding?
Strong, irregular contractions similar to phase 2 of fasting (SOME propagate, some not)
