GI tract motility Flashcards
Types of Gi motility
peristalsis
segmentation
migrating motility complexes
when nutrient are present and digestive/absorptive process is ongoing.
digestive/absorptive period
interdigestive/post-absorptive
when digestion and absorption of nutrients are completed
what is the mechanism of GI motility?
Basic Electrical Rhythm
Electric membrane potential in GI smooth muscle cells (SMCs)are not stable, they spontaneously fluctuate constantly
-80/-40
t/f BER is a fast wave
false, is slow
interstitial cells of Cajal
pacemaker cells that initiate the slow wave and spreads to adjacent smooth muscle cells
the depolarization caused by the slow wave causes what channels to open
Ca
the nerual stimulus is transmited to smooth m. cells by
ICC network, pacemaker cells
slow wave causes what type of contraction
minor contractions
spike potentials cause what type of contraction of smooth m. cells
major contraction of smooth m. cells
3 stimulis causing spike potentials
stretch
ACh
PSNS-pilocarpine
in slow wave there is no action potential, what Ca channels are open?
transient Ca channels
spike potentials occur action potentials, what type of Ca channel are opened?
long lasting calcium channels
From esophagus to rectum:
A circular contraction behind the bolus stretch and an area of circular relaxation in front of it.
A longitudinal contraction for propulsion
peristalsis
peristalsis requires an active_____ and _______INTEGRATION
myenteric plexus = Auerbach’s plexus and ENS
A bolus of chyme stimulates
intrinsic afferents (sensory neurons with cell bodies in the myenteric plexus) that activate enteric interneurons, which in turn stimulate enteric motor neurons
eneteric motor neurons inn.
smooth m. cells and cells of cajal
Longitudinal smooth muscle contraction for anterograde direction is stimulated by the neurotransmitters
ACh
Circular smooth muscle contraction is stimulated by the neurotransmitters
ABOVE THE BOLUS
ACh
substance P
Circular smooth muscle relaxation is stimulated by
BELOW THE BOLUS
nitric oxide (NO) and vasoactive intestinal peptide (VIP)
Mostly occurs in small intestine:
Localized contractions of circular smooth muscle only.
No longitudinal contraction for propulsion
Segmentation
help mix chyme in intestine
segmentation
These contractions isolate (squeeze) small sections of the intestine, moving their contents back and forth while continuously subdividing, breaking up, and mixing the contents.
segmentation
It is also called a ‘housekeeping wave’,
induces peristalsis
occurs every 90–120 minutes during fasting
MMC migrating motor complex
responsible for stomach growling when hungry
MMC
triggers peristalsis waves
facilitate removal of indigestible substances past ileocecal sphincter into colon
transports bacteria from small to large intestine and inhibit mkigartion of colonic bacteria back into ileum
MMC
impairment of MMC causes
bacterial overgrowth
t/f MMC is a giant contraction
true
No spike potential, no contraction. Lasting 45-120min, a prolonged period of quiescence
PHASE 1 of MMC
Irregular (sporadic) spike potential and contraction. Lasting 20-30min
phase 2 of MMC
Regular (intense) spike potential and contraction. Lasting 5–10 minutes;
phase 3 of MMC
