GI Motility Flashcards
the trade off for the efficiency of smooth vs. skeletal muscle is
speed of contractions
what part of GI does phasic contractions
antral stomach
SI
large intestine
what part of GI does tonic contractions
sphincters
what is tonus
maintained state of partial contraction
what does BER stand for
basic electric rhythm
oscillating membrane potential is called
slow waves or BER
what is another name for BER
slow waves
what does BER do
sets pace for contractions
slow waves are initiated by
pacemaker cells
what is the name of the pacemaker cell of GI
Interstitial cells of Cajal (ICC
what does ICC stand for
Interstitial cells of Cajal
how many waves per min for stomach
3
how many waves per min for SI
11-12
how many waves per min for large intestine
2-13
hormones can change what regarding contractions
amplitude but not frequency
if there is no extrinsic innervation, GI muscles contract in response to
stretch
electrical slow waves in SI are always
present
even without AP, smooth muscle is not completely relaxed in SI, it exhibits
tonic contraction
if there is action potential on top of slow waves, what happens
phasic contraction
the greater the number of AP on top of slow wave, the
larger the phasic contraction
describe twitches of smooth muscle compared to skeletal
in smooth there are not separate twitches, the twitches summate to one long contraction
AP are generated in response to
neural stimulation
hormonal stimulation
stretching the muscle
what does Ach do to GI
increase strength of contraction by increasing Ca2+ in cells
how does Ach increase strength of contraction
by increasing Ca2+ in cells
what does NE do to GI
inhibits contraction
where are ICC found
stomach
proximal duodenum
mid colon
what set the rate of BER
ICC
how do ICC set rate of BER
gap junction coupling
what are the two motility patterns the enteric NS encodes
segmental & peristaltic
when is the segmental pattern dominant
after eating
what does post-prandial mean
after a meal
when is the peristaltic pattern dominant
fasting
what part of GI does central nervous system have total control
proximal esophagus & anus
what part of GI does central nervous system have partial control
distal esophagus, stomach, and colon
what part of GI does central nervous system have almost no control
SI
what is the major mode of unidirectional propulsion
peristalsis
what contraction type promotes mixing and can limit transit
segmental (rhythmic) contraction
what is another name for segmental contraction
rhythmic
what kind of contractions block transit
tonic
draw out the sphicnters
pg 12
how are sphincters contracted
tonically
describe control of swallowing
initially voluntary but becomes involuntary
what are the three phases involved in swallowing
oral
pharyngeal
esophageal
describe the oral phase
initiated voluntarily by the movement of food to the back of the mouth
describe the pharyngeal phase
reflexive and peristaltic
describe the esophageal phase
slower and peristaltic
what coordinates the involuntary swallowing process
swallowing center in medulla
what kind of receptors are in swallowing center
Somatosensory receptors in the pharynx stimulate the swallowing center in the medulla
what is inhibited in pharyngeal phase
breathing
what covers larynx opening in pharyngeal phase
Epiglottis
what is purpose of epiglottis covering larynx
prevents food from going into trachea
in esophageal phase, bolus is moved down esophageus by
perimary peristaltic wave
if primary peristaltic wave does not clear esophagus, what happens
secondary peristaltic wave
what controls esophageal phase
partly reflexive and partly ENS
1 second of stimulation for initiation of swallowing leads to
9 seconds of programmed muscle contraction
list the steps of esophagus reflex
pg 15
when a person isn’t swallowing what is happening with esophageal sphincter
contracted
when a person isn’t swallowing what is happening with glottis
open