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PSL301 > Digestion 2: Motility > Flashcards

Digestion 2: Motility Flashcards

1
Q

which layer of the muscle is closer to the lumen? what is its function?

A

circular layer;

decrease diameter of the GI tract

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2
Q

which layer of muscle is further from the lumen? what is it’s function?

A 
longitudinal layer (lies on top of the circular layer);
shortens the GI tract
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3
Q

GI motility is generally controlled by…

A

ENS

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4
Q

Function of motility

A

1) move food from mouth → anus
2) mixing: helps absorption
3) mechanical breakdown

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5
Q

the smooth muscles that line the GI are innervated by…

A

ANS (involuntary), which release NT to send AP through the smooth muscle system

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6
Q

distal end of autonomic neurons have ____

A

varicosities filled with NT

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7
Q

smooth muscles of the GI propagate AP by…

A

gap junctions

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8
Q

contraction of smooth muscles in the GI. why?

A

contract as 1 unit;

AP relayed through all interconnected smooth muscles

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9
Q

how might an AP in the GI smooth muscles happen?

A

slow wave potentials that reach threshold will fire an AP

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10
Q

slow wave potentials

A

rhythmic depolarization & repolarization of membrane potentials, but doesn’t always reach threshold

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11
Q

force & duration of muscle contractions depend on…

A

amplitude & frequency of the AP

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12
Q

frequency of AP in the GI depend on…

A

slow wave potentials

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13
Q

some specialized smooth muscle cells have ____ activity, meaning they generate ____.

A

pacemaker;

slow wave potentials generators (allow cells beside them to generate slow waves)

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14
Q

smooth muscle cells with pacemaker activity is called…

A

interstitial cells of Cajal

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15
Q

interstitial cells of Cajal (ICC) are responsible for…

A

Generating slow wave potentials in normal muscle cells; propagates through gap junctions

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16
Q

amplitude of slow wave potentials generated by ICC as a function of distance

A

amplitude decreases over time as the waves travel

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17
Q

can smooth muscle cells generate slow wave potential?

A

no

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18
Q

where are ICCs located?

A

all regions & layers of the GI tract

- @ interface between nerve fibers & smooth muscle cells

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19
Q

frequency of slow waves depend on…

A

where they are located

  • higher in small intestines
  • lower in stomach
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20
Q

difference between pacemaker in GI and in heart

A 
heart:
- frequency 80/min (steady)
- always reach threshold
- nodes
ICC:
- frequency varies through GI
- no nodes (emit slow waves anywhere)
- does not always reach threshold
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21
Q

ICC pacemaker activity is not dependent on… BUT…

A

neural / hormone input;

can be MODULATED by neural & hormone input

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22
Q

PNS effect on ICC pacemaker activity

A

Depolarize → easier for slow waves reach AP

- almost guaranteed to have AP every time if there is PNS stimulation

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23
Q

SNS effect on ICC pacemaker activity

A

hyperpolarize → difficult for slow waves to reach AP

  • few contractions
  • slow waves flatten → no oscillations
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24
Q

what stimulates depolarization of ICC?

A
  • stretch
  • PNS
  • hormones: cholecystokinin, gastrin
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25
Muscles in GI are influenced by...
- ICC - ENS - PNS / SNS - hormones
26
main effect of hormones: motility // secretion?
secretion
27
which hormones increase gut motility?
motilin
28
which hormones decrease gut motility?
CCK, secretin
29
mass movement is specific to...
large intestines
30
__ and __ regulate movement between different regions of the GI
sphincters; | valves
31
MMC stands for...
migrating motor complex
32
MMC is specific to...
motility pattern specific to interdigestive state (between meals)
33
define: MMC
waves of activity that sweep through the intestines in a regular cycle during a fasting state - trigger peristalsis - gets rid of indigestible material to anus
34
MMC begins in the ... and goes to...
in the stomach; | small intestines
35
if particles in stomach are larger than __, they are not allowed to leave
1 mm
36
function of MMC
- stomach: flushes > 1mm food particles out of stomach - small intestines: flush bile through - sweeps up bacteria
37
disruption of MMC is associated with...
bacteria overgrowth
38
MMC is coordinated by...
ENS
39
3 phases of MMC
3) regular contractions of circular muscles 2) irregular contractions 1) no contractions
40
1 MMC cycle takes about ___ min. It will continue until...
80 - 110; | cycles from stomach to small intestines until there is FOOD in the duodenum (nutrients will not stop MMC)
41
Material in the stomach will stop MMC at...
the stomach, but MMC will still occur in the small intestine
42
motilin is secreted by...
M cells in crypts of duodenum & jejunum
43
which hormone regulates MMC in humans?
motilin
44
when is motilin secreted?
during interdigestive state
45
Motilin acts on ___ neurons and ____ cells to regulate (but NOT ____) MMC
myenteric; smooth muscle; initiate
46
DEGLUTITION
process of swallowing
47
steps of deglutition
1) tongue pushes bolus against soft palate → triggers swallowing reflex & closes nasal cavity 2) upper esophageal sphincter relaxes, epiglottis close to keep material out of lungs 3) food moves down esophagus (peristalsis & gravity), upper esophageal sphincter contracts
48
voluntary swallowing is initiated by...
- front of tongue pushing against hard palate | - something must be in mouth
49
___ is inhibited during swallowing
respiration
50
___ controls involuntary swallowing (at ____)
ANS; | lower esophagus
51
CNS control of swallowing (voluntary)
food → CN IX, X → swallowing center in medulla/lower pons → CN V, IX, X, XII → movement of tongue
52
CN IX
glossopharyngeal never
53
CN X
vagus nerve
54
CN V
trigemial never
55
CN XII
hypoglossal nerve
56
CNS control of swallowing (involuntary)
food in pharynx → CN X → swallowing center → CN V, VII, IX, X, XII
57
CN VII
facial nerve
58
involuntary swallowing process
1) food against soft palate → CNS 2) larynx moves forward allowing bolus go down pharynx, epiglottis & trachea closes 3) after bolus enters esophagus, upper esophageal sphincter closes
59
___ pushes food into esophagus
base of tongue
60
CNS control of esophagus
food enters the stomach → CN X → swallowing center → CN X → myenteric plexus → peristalsis in esophagus & relaxation of lower esophageal sphincter
61
peristalsis is stimulated by...
distension
62
steps of peristalsis
1) contraction of circular muscles behind food 2) contraction of longitudinal muscles ahead of food 3) contraction of circular muscle layer forces food mass forward
63
PERISTALSIS
cycle of contractions & relaxations of circular muscle & longitudinal muscles
64
2 types of peristalsis
1. primary | 2. secondary
65
primary peristalsis
bolus into pharynx → top of esophaglus
66
primary peristalsis is driven by...
extension of the esophagus
67
when does secondary peristalsis occur? When does it stop?
when bolus gets stuck in esophagus / primary peristalsis couldn't push it down; until stuck bolus enters the stomach
68
process of secondary peristalsis
1) triggered by food stuck in esophagus - stretch receptors (local reflex) 2) push bolus down to stomach
69
secondary peristalsis is controlled by..
medulla oblongata
70
peristalsis in esophagus is controlled by...
entirely by ENS
71
purpose of excitatory & inhibitory neurons of the ENS during peristalsis
excitatory: contract muscles behind & around bolus inhibitory: relax muscles in front of bolus
72
which NT are responsible for excitatory neurons controlling peristalsis?
ACh, substance P
73
which NT are responsible for inhibitory neurons controlling peristalsis?
NO, vasoactive intestinal peptide, ATP
74
what is triggered when gastric contents splash up the esophagus?
peristalsis activated: | - irritants on lining of esophagus activates secondary peristalsis
75
orad portion of stomach
closer to mouth
76
receptive relaxation
relaxation of orad portion of stomach to make room for food entering
77
receptive relaxation is initiated by ___ reflex
vagovagal
78
vagovagal reflex
Stomach → brain → stomach reflex 1) afferent fibres from stomach → dorsal-vagal complex in medulla 2) efferent muscle fibre → allow stretch to happen
79
cutting the vagus nerve will stop ___ , but not ___
receptive relaxation; | peristalsis
80
what happens if there is no receptive relaxation?
no stretch happens when food enters stomach → pain
81
vagovagal reflex integrates...
dorsal vagal complex
82
caudad portion
lower portion of stomach
83
mechanical digestion in the stomach
retropulsion - peristalsis cause high pressure chyme - grinds food particles against each other
84
purpose of segmentation
- move food back and forth, allowing for mixing of chyme with digestive enzymes in small intestines - more time for absorption
85
what cells absorb nutrients in the small intestines?
transport epithelial cells
86
there is higher frequency of segmentation in the ___ portion of the small intestine than the __ portion
proximal; | distal
87
peristalsis in the small intestines is due to...
change in segmentation frequency at the various regions
88
which movement pattern does not propel the material forward?
segmentation
89
Segmentation
localized concentric contractions of circular muscles | *Think: squeeze right fist then left alternating
90
purpose of ileocecal valve
- control emptying of small intestines → large intestines | - prevent backflow
91
how to open ileocecal valve? how to close?
open: distension of ileum & gastroileal reflex close: distension / buildup of chyme in cecum
92
ileum empties into ___
cecum
93
gastroileal reflex
presence of food in the stomach cause ileocecal valve to open
94
mass movement happens at... (specific)
large intestines: transverse colon & some parts of descending colon
95
Which segment of the large intestines is used as a storage area?
sigmoid colon
96
dehydration of feces occurs in the ... (specific)
transverse colon
97
gastrocolic reflex
presence of food in the stomach initiates mass movement (to make room for new food coming in)
98
gastrocolic reflex is controlled by...
ENS
99
__ stimulates mass movement, while ___ inhibits it
PNS; | SNS
100
frequency of mass movement
1-3 times / day (after meals)
101
mass movement
infrequent waves of contraction in the large intestines that move content large distances at a slow rate
102
process of defecation
1) pressure in rectum → ENS → peristalsis in rectum & relaxation of internal sphincter 2) distension also stimulate PNS → enhance mass movement in descending & sigmoid colon 3) relaxation of external sphincter if appropriate 4) contraction of abs → expulsion of feces
103
defecation is the result of..
mass movement
104
what happens when we want to poop but no toilet?
feces move back up sigmoid colon until next mass movement
105
EMESIS
vomitting
106
where in the brain is responsible for emesis?
vomiting center in medulla
107
body responses to emesis goes through which nerves/areas?
- vagus - spinal nerves - phrenic nerve - stomach
108
emesis: vagus nerve
- enhance salivation (lube) - relax esophagus & lower esophageal spincter - contract pylorus (lower stomach)
109
emesis: spinal nerves
- inspiration (less pressure on esophagus) | - contract abs (pressure)
110
emesis: phrenic nerve
diaphragm descend
111
emesis: stomach
reverse peristalsis

PSL301 (29 decks)

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