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Physiology Exam 3 > Lecture 3: Gastrointestinal Motility > Flashcards

Lecture 3: Gastrointestinal Motility Flashcards

1
Q

Name the three things that motility accomplishes

A

Grinding, mixing, breakdown of fragments and ingested food

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2
Q

Contractile tissue of GIT is composed of:

A

Smooth muscle
Striated muscle in pharynx, upper 1/3 of esophagus, external anal sphincter

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3
Q

What type of smooth muscle allows for very smooth muscle contractions?

A

Unitary smooth muscle

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4
Q

Unitary smooth muscles cells are __________ coupled via __________

A

Electrically; gap junctions

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5
Q

Circular muscle decreases ________ of that segment

A

Diameter

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6
Q

Longitudinal muscle decreases ________ of that segment

A

Length

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7
Q

Periodic contractions followed by relaxation

A

Phasic contractions

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8
Q

What type of contractions maintain a constant level of contraction or tone without regular relaxation?

A

Tonic contractions

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9
Q

Where do phasic contractions take place?

A

Esophagus, gastric antrum, SI

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10
Q

Where do tonic contractions take place?

A

Upper region of stomach, lower esophageal region, ileocecal and internal anal sphincters

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11
Q

T/F: Slow waves always bring membrane potential to threshold

A

False

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12
Q

T/F: Slow waves are always present

A

True

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13
Q

T/F: APs are always present

A

False

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14
Q

What happens when a slow wave causes an AP?

A

Contraction

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15
Q

What determines direction and velocity of contractions?

A

Slow waves

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16
Q

What is the frequency of slow waves in the stomach?

A

3 per minute

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17
Q

What is the frequency of slow waves in the duodenum?

A

12 per minute

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18
Q

T/F: Frequency of slow waves is not influenced by neural or hormonal input

A

True

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19
Q

What ion causes the depolarizing phase and maintenance of the plateau of slow waves?

A

Calcium

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20
Q

What ion is responsible for repolarization of slow waves?

A

Potassium

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21
Q

Name the 3 phases of swallowing

A

Oral phase
Pharyngeal phase
Esophageal phase

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22
Q

Oral phase, voluntary or involuntary?

A

Voluntary at first then becomes involuntary

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23
Q

Name the phase of swallowing:
Tongue forces bolus toward pharynx, lots of receptors, then involuntary swallowing takes over

A

Oral phase

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24
Q

Name the phase of swallowing:
Involuntary, propel bolus from mouth through pharynx to esophagus in 4 steps

A

Pharyngeal phase

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25
Q

Name the phase of swallowing:
Controlled by swallowing reflex AND enteric nervous system
Propels bolus through esophagus to stomach
After bolus enters esophagus, swallowing reflex closes sphincter

A

Esophageal phase

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26
Q

In pharyngeal phase, what pulls up so that food cannot move into nasopharynx?

A

Soft palate

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27
Q

In pharyngeal phase, what moves to cover the opening to the larynx?

A

Epiglottis

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28
Q

In pharyngeal phase, when the larynx moves up against the epiglottis, what is covered?

A

Trachea

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29
Q

In pharyngeal phase, what relaxes so food can pass from pharynx to esophagus?

A

Upper esophageal sphincter

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30
Q

In pharyngeal phase, what propels the bolus through the sphincter?

A

Peristaltic wave

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31
Q

What is the esophageal phase controlled by?

A

Swallowing reflex and enteric nervous system

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32
Q

In the esophageal phase, after the bolus enters the esophagus, what reflex closes the sphincter?

A

Swallowing

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33
Q

In the esophageal phase, what pushes the bolus down?

A

Primary peristaltic wave

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34
Q

In the esophageal phase, what happens if the esophagus is still distended (food still in it) after the primary peristaltic wave?

A

Secondary peristaltic wave

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35
Q

Why is esophageal motility needed?

A

To propel bolus from pharynx into the stomach

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36
Q

What is the action of the primary peristaltic contraction?

A

Creates high pressure area behind bolus

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37
Q

What opens as the peristaltic wave and bolus reach it?

A

Lower esophageal sphincter

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38
Q

What is the lower esophageal sphincter mediated by?

A

Vagus nerve and VIP

39
Q

Why is the bolus allowed to move into the stomach?

A

Lower pressure than in esophagus

40
Q

What difference is there between the upper and lower esophagus?

A

Pressure difference

41
Q

Where in the esophagus is pressure lower?

A

Upper

42
Q

What are the three muscle layers of the stomach?

A

Outer longitudinal
Inner circular
Inner oblique

43
Q

What region of the stomach is thin walled?

A

Orad

44
Q

What region of the stomach is thick walled for stronger contractions?

A

Caudad

45
Q

The orad stomach relaxes due to

A

Relaxation of lower esophageal sphincter

46
Q

What does relaxation of the orad stomach do to pressure and volume of the stomach?

A

Decreases pressure
Increases volume

47
Q

What reflex is involved in the relaxation of the stomach?

A

Vasovagal

48
Q

For the vasovagal reflex, what is carried on the vagal nerve?

A

Both afferent and efferent limbs

49
Q

Name the three components of gastric motility

A

Relaxation of orad region
Contractions
Gastric emptying

50
Q

What is the purpose of contractions in gastric motility?

A

Reduce bolus size and mix with gastric secretion

51
Q

What do gastric secretion consist of?

A

HCl and Pepsin

52
Q

Describe the path of the contraction waves of gastric motility (begin and move towards where)

A

Begin in middle of body
Move distally along caudal stomach towards pylorus

53
Q

When waves are propelled back and further decrease particle size, what is this called?

A

Retropulsion

54
Q

For slow waves, neural input and hormones can’t alter frequency, but can alter

A

Contraction strength

55
Q

Force of contractions can be increased via

A

PSNS, gastrin, motilin

56
Q

Force of contractions can be decreased via

A

SNS, secretin, GIP

57
Q

Migrating myoelectric complexes are mediated by

A

Motilin

58
Q

What causes migrating myoelectric complexes to occur, and how often?

A

During fasting state at about 90 minute intervals

59
Q

What does gastric emptying consist of?

A

Chyme entering small intestines

60
Q

How often do slow waves occur in duodenum?

A

12 per minute

61
Q

How often do slow waves occur in ileum?

A

9 per minute

62
Q

What coordinates segmentation and peristaltic contractions in the SI?

A

Enteric nervous system

63
Q

Parasympathetic innervates the SI via what

A

Vagus nerve

64
Q

Sympathetic innervates SI via

A

Celiac and superior mesenteric ganglia

65
Q

Parasympathetic innervations will do what to contraction strength?

A

Increase

66
Q

Sympathetic innervations will do what to contraction strength?

A

Decrease

67
Q

What muscle do segmental contractions occur in? (SI)

A

Circular muscle

68
Q

What is the purpose of segmental contraction?

A

Mix chyme expose to pancreatic enzymes

69
Q

Describe movement of segmental contractions

A

Back and forth movement to mix, but NO forward movement

70
Q

T/F: Segmental contractions contain forward movement

A

False

71
Q

What kind of contraction propels chyme toward LI?

A

Peristaltic contractions

72
Q

What kind of muscle involved in peristaltic contractions?

A

Circular and longitudinal

73
Q

Where does the contraction occur in relation to the bolus?

A

Contraction behind bolus, relaxed in front of bolus

74
Q

What kind of cells sense the bolus?

A

Enterochromaffin cells

75
Q

What triggers the peristaltic reflex for moving chyme?

A

Bolus sensed by enterochromaffin cells

76
Q

Explain the course of events that trigger the vomiting reflex

A

Information from vestibular system
Back of throat
GIT and chemoreceptor trigger zone in 4th ventricle?
Vomiting center in medulla
Vomiting reflex

77
Q

Explain the events of the vomiting reflex

A

Reverse peristalsis in SI
Relaxation of stomach and pylorus
Increased abdominal pressure
Movement of larynx up, relaxation of lower esophageal sphincter, closure of glottis
Forceful expulsion

78
Q

During retching, what remains closed

A

Upper esophageal sphincter

79
Q

During retching, what remains open

A

Lower esophageal sphincter

80
Q

What opens to allow contents from SI into cecum?

A

Ileocecal sphincter

81
Q

Describe the course of contents through colon

A

Ascending, transverse, descending, sigmoid colon to rectum and anal canal in ruminants in pigs

82
Q

What do ruminants and pigs have that horses, cats, and dogs don’t?

A

Sigmoid colon

83
Q

Segmentation contraction occurs in which parts of LI?

A

Cecum and proximal colon

84
Q

Segmentation contractions in cecum and proximal colon are associated with what?

A

Haustra

85
Q

Define haustra

A

Saclike segments

86
Q

Do dogs, rats, carnivores, ruminants have haustra?

A

No

87
Q

Do guinea pigs, rabbits, pigs, humans, monkeys, horses have haustra?

A

Yes

88
Q

The mass movements in the LI have what goal?

A

Move contents over long distances

89
Q

How often do mass movements in the LI occur?

A

1-3 times a day

90
Q

External anal sphincter is _______ contracted until defecation

A

Tonically

91
Q

What contracts to create pressure on the external anal sphincter?

A

Smooth muscle

92
Q

Retosphincteric reflex

A

When internal anal sphincter relaxes when rectum fills

93
Q

Gastrocolic reflex

A

Distention of stomach increases motility of colon

94
Q

Gastrocolic reflex is afferent where and efferent where?

A

Afferent in stomach
Efferent in colon

Physiology Exam 3 (13 decks)

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