Digestion 2: Motility Flashcards Preview

PSL301 > Digestion 2: Motility > Flashcards

Flashcards in Digestion 2: Motility Deck (111):
1

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

circular layer;
decrease diameter of the GI tract

2

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

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

3

GI motility is generally controlled by...

ENS

4

Function of motility

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

5

the smooth muscles that line the GI are innervated by...

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

6

distal end of autonomic neurons have ____

varicosities filled with NT

7

smooth muscles of the GI propagate AP by...

gap junctions

8

contraction of smooth muscles in the GI. why?

contract as 1 unit;
AP relayed through all interconnected smooth muscles

9

how might an AP in the GI smooth muscles happen?

slow wave potentials that reach threshold will fire an AP

10

slow wave potentials

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

11

force & duration of muscle contractions depend on...

amplitude & frequency of the AP

12

frequency of AP in the GI depend on...

slow wave potentials

13

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

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

14

smooth muscle cells with pacemaker activity is called...

interstitial cells of Cajal

15

interstitial cells of Cajal (ICC) are responsible for...

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

16

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

amplitude decreases over time as the waves travel

17

can smooth muscle cells generate slow wave potential?

no

18

where are ICCs located?

all regions & layers of the GI tract
- @ interface between nerve fibers & smooth muscle cells

19

frequency of slow waves depend on...

where they are located
- higher in small intestines
- lower in stomach

20

difference between pacemaker in GI and in heart

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

21

ICC pacemaker activity is not dependent on... BUT...

neural / hormone input;
can be MODULATED by neural & hormone input

22

PNS effect on ICC pacemaker activity

Depolarize → easier for slow waves reach AP
- almost guaranteed to have AP every time if there is PNS stimulation

23

SNS effect on ICC pacemaker activity

hyperpolarize → difficult for slow waves to reach AP
- few contractions
- slow waves flatten → no oscillations

24

what stimulates depolarization of ICC?

- stretch
- PNS
- hormones: cholecystokinin, gastrin

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