GI Motility Flashcards
1
Q
the trade off for the efficiency of smooth vs. skeletal muscle is
A
speed of contractions
2
Q
what part of GI does phasic contractions
A
antral stomach
SI
large intestine
3
Q
what part of GI does tonic contractions
A
sphincters
4
Q
what is tonus
A
maintained state of partial contraction
5
Q
what does BER stand for
A
basic electric rhythm
6
Q
oscillating membrane potential is called
A
slow waves or BER
7
Q
what is another name for BER
A
slow waves
8
Q
what does BER do
A
sets pace for contractions
9
Q
slow waves are initiated by
A
pacemaker cells
10
Q
what is the name of the pacemaker cell of GI
A
Interstitial cells of Cajal (ICC
11
Q
what does ICC stand for
A
Interstitial cells of Cajal
12
Q
how many waves per min for stomach
A
3
13
Q
how many waves per min for SI
A
11-12
14
Q
how many waves per min for large intestine
A
2-13
15
Q
hormones can change what regarding contractions
A
amplitude but not frequency
16
Q
if there is no extrinsic innervation, GI muscles contract in response to
A
stretch
17
Q
electrical slow waves in SI are always
A
present
18
Q
even without AP, smooth muscle is not completely relaxed in SI, it exhibits
A
tonic contraction
19
Q
if there is action potential on top of slow waves, what happens
A
phasic contraction
20
Q
the greater the number of AP on top of slow wave, the
A
larger the phasic contraction
21
Q
describe twitches of smooth muscle compared to skeletal
A
in smooth there are not separate twitches, the twitches summate to one long contraction
22
Q
AP are generated in response to
A
neural stimulation
hormonal stimulation
stretching the muscle
23
Q
what does Ach do to GI
A
increase strength of contraction by increasing Ca2+ in cells
24
Q
how does Ach increase strength of contraction
A
by increasing Ca2+ in cells
25
what does NE do to GI
inhibits contraction
26
where are ICC found
stomach
proximal duodenum
mid colon
27
what set the rate of BER
ICC
28
how do ICC set rate of BER
gap junction coupling
29
what are the two motility patterns the enteric NS encodes
segmental & peristaltic
30
when is the segmental pattern dominant
after eating
31
what does post-prandial mean
after a meal
32
when is the peristaltic pattern dominant
fasting
33
what part of GI does central nervous system have total control
proximal esophagus & anus
34
what part of GI does central nervous system have partial control
distal esophagus, stomach, and colon
35
what part of GI does central nervous system have almost no control
SI
36
what is the major mode of unidirectional propulsion
peristalsis
37
what contraction type promotes mixing and can limit transit
segmental (rhythmic) contraction
38
what is another name for segmental contraction
rhythmic
39
what kind of contractions block transit
tonic
40
draw out the sphicnters
pg 12
41
how are sphincters contracted
tonically
42
describe control of swallowing
initially voluntary but becomes involuntary
43
what are the three phases involved in swallowing
oral
pharyngeal
esophageal
44
describe the oral phase
initiated voluntarily by the movement of food to the back of the mouth
45
describe the pharyngeal phase
reflexive and peristaltic
46
describe the esophageal phase
slower and peristaltic
47
what coordinates the involuntary swallowing process
swallowing center in medulla
48
what kind of receptors are in swallowing center
Somatosensory receptors in the pharynx stimulate the swallowing center in the medulla
49
what is inhibited in pharyngeal phase
breathing
50
what covers larynx opening in pharyngeal phase
Epiglottis
51
what is purpose of epiglottis covering larynx
prevents food from going into trachea
52
in esophageal phase, bolus is moved down esophageus by
perimary peristaltic wave
53
if primary peristaltic wave does not clear esophagus, what happens
secondary peristaltic wave
54
what controls esophageal phase
partly reflexive and partly ENS
55
1 second of stimulation for initiation of swallowing leads to
9 seconds of programmed muscle contraction
56
list the steps of esophagus reflex
pg 15
57
when a person isn't swallowing what is happening with esophageal sphincter
contracted
58
when a person isn't swallowing what is happening with glottis
open
59
when person isn't swallowing what is happening with epiglottis
up
60
when is swallowing reflex triggered
when bolus of food reaches the pharynx
61
how does body prevent food from entering trachea
larynx moves up and tips epiglottis over glottis
62
calcium activated potassium channel will produce
repolarization
63
what kind of receptors in back of throat
tactile receptors
64
draw out the vagus nerve and it's innervation in the esophageal phase
pg 18
65
what is the only esophageal motility pattern
peristalsis
66
does esophageal muscle have spontaneous contraction
no
67
draw out the peristalsis of esophageal in regards to what is relaxing and what is contracting as a bolus travels
pg 19
68
draw out the peristalsis mechanism, specifically with the inhibitory interneuron and the excitatory interneuron
pg 20
69
what is the purpose of swallowing manometry
can see if peristalsis is behaving correctly
70
how is the LES different from the UES?
LES has thick band of muscle and will form vestibule (pocket) so acid doesn't leak out
71
LES is innervated by
vagal excitatory fibers
| vagal inhibitory fibers
72
relaxation of LES is associated with what happening in its innervation
increased frequency of AP for vagal inhibitory fibers
| decreased frequency of AP for vagal excitatory fibers
73
what portion of stomach must relax to accept food bolus
orad
74
what are the three anatomic regions of the stomach
fundus
body
antrum
75
what does fundus do during feeding
relaxes
76
the fundus relaxes during feeding, this is called
receptive relaxation/accomodation
77
what is the orad portion of the stomach
thin walled, receives food bolus through receptive relaxation
78
the stomach can accomodate large volumes without change in
pressure
79
receptive relxation is what kind of reflex
vagovagal
80
vagovagal reflex in stomach is elicited by
stretching of the stomach
81
what does CCK do to the orad area
makes it more distendible
82
what is the caudad portion of the stomach
thick walled, produces contractions
83
where does contraction begin in the stomach
middle of body through caudad
84
what is Retropulsion
Not all chyme goes into duodenum as contractions also close pylorus propelling contents back into stomach for further mixing and reduction
85
what is function of pyloric sphincter
sieves material, prevents particles that are too big (more than 1 mm) from leaving stomach
prevents reflux of duodenal material
86
what 2 major factors slow or inhibit gastric emptying
Fat & H+ in duodenum
87
effects of fat is mediated by
CCK
88
if there is too much H+ in stomach what happens
deteced by ENS
slows gastric smooth muscle
permits more time for HCO3- to neutralize
89
before a solid meal can be emptied from the stomach, there is what phase
lag phase
90
what is the lag phase
allows time for the food to be reduced to small enough size to enter SI
91
PNS increases contraction of SI through what 4 neuropeptides
ACh, Substance P, enkephalins, motilin
92
what are the two patterns of contraction in the SI
segmentation & peristaltic
93
what is quiescent contraction
no contraction
94
what are the phases of fasting motility pattern
I: quiescent
II: random contractions
III: migrating myoelectric complex
95
what does MMC stand for
migrating myoelectric complex
96
phase III/MMC is correlated with rise in levels of what hormone
motilin
97
how long does it take MMC to move down SI
90 min
98
what is the fed motility pattern
irregular spikes from meals → segmental contractions mixed with short perstalic waves
99
what is the function of segmented contraction
mixes food and exposes it to all the "juices"
100
what happens when intestines contract in segmented contraction in SI
bolus of food is split in orad and caudad directions
101
what happens when intestins relax in segmented contraction in SI
the split bolus merges back together
102
what is the function of peristalic contraction in SI
propels chyme along SI to LI
103
what neurotransmitters are involved in orad contraction
ACh & Substance P
104
what neurotransmitters are involved in caudad relxation
VIP
| NO
105
peristalic reflex of SI depends on what nervous system
enteric
106
intestinointestinal reflex depends on what nervous system
extrinsic
107
what is purpose of Intestinointestinal reflex
Severe distention in one area inhibits contractions in the remaining bowel.
108
describe the peristaltic reflex in SI
Distention of the SI causes contraction above and relaxation below distension.
109
describe the Gastroileal reflex in SI
Movement of ileal contents into large intestine is stimulated by the presence of food in the stomach
110
emesis =
vomitting
111
prlonged vomitting can result in
alkalosis, hypokalemia, and dehydration.
112
retching =
dry heaving
113
in dry heaving, what happens regarding UES & LES
LES open
| UES closed
114
what are the main anatomical regions of LI
ascending, transverse, descending, sigmoid colon and the rectum
115
what kind of contractions occur in cecum and proximal colon of LI
segmentation contractions
116
movements in colon are coordinated by
BER
117
describe segmented contraction in LI
occur in cecum and proximal colon: mixes contents; are associated with sac-like segments called haustra. Fibers in external muscle layer form outpouchings.
118
the colon is divided into segments called
haustra
119
b/w haustral pockets there are
segments of contracted circular muscle
120
what do inhibitory neurons do regarding haustra
they maintain the relxation in the haustra/pockets
121
segmented contractions in LI facilitate
absorption
122
describe the Colonocolonic reflex
Distention of one part of the colon elicits reflex relaxation in other parts of the colon → partly mediated by the sympathetic fibers
123
describe the Gastrocolic reflex
The motility of proximal and distal colon and the frequency of mass movements increase after a meal enters the stomach.
124
colonocolic reflex is mediated by
sympathetic fibers
125
the gastrocolic reflex is mediated by
CCK & gastrin
126
Rectosphincteric reflex is also called
defecation reflex
127
describe the Rectosphincteric reflex
As rectum fills with feces, smooth muscle wall contracts in the rectum and internal anal sphincter relaxes – no defecation as external anal sphincter tonically contracted
128
when do you get the urge to defecate
when the rectum is filled to 25% of its capacity
129
what does the Valsalva maneuver do
increase intra-abdominal pressure
130
what does CCK do to gastric emptyin
inhibits
131
describe the defecation reflex
pg 41
132
during mass movement of colon what happens
segmentation stops and haustra disappear, peristaltic contractions move material from one section to another
133
why does H+ slow down gastric emptying
too much hydrogen means digestive enzymes wont work need bicarb.
134
compare gastric emptying depending on composition of meal
solid goes much slower than semisolid which goes slower than liquid
135
after 60 min how much of solid meal is still in stomach
60%
136
if there is semisolid meal how much is still in stomach after 60 min
40%
137
if there is liquid meal how much is in stomach after 60 min
10%
138
what is lag phase?
secretions
| mechanical breakdown
139
is there lag phase for liquid
no
140
MMC starts where
antrum of stomach
141
MMC cycle is how long
90 min
142
what is major pattern after meal
rhythmic segmentation
143
how does segmentation contraction work
contract right in the middle of the food bolus until its small enough to move forward
144
contracting in peristaltic contraction via
Ach
| Substace P
145
relaxing in peristaltic contraction via
VIP
| NO
