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Veterinary Physiology > Gastrointestinal Motility > Flashcards

Gastrointestinal Motility Flashcards

1
Q

What does motility refer to?

A

contraction and relaxation of walls and sphincters of the GIT
- accomplishes grinding, mixing, and fragmenting food

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2
Q

The contractile tissue of the GIT is composed of?

A

smooth muscle and striated muscle in upper 1/3rd of esophagus, external anal sphincter

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3
Q

What allows for very smooth contraction?

A

unitary smooth muscle

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4
Q

What does unitary smooth muscle have?

A

cells electrically coupled via gap junctions
signals spread rapidly —> allows for smooth contraction

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5
Q

List the types of contractions of smooth muscle in the GIT.

A

phasic contractions
tonic contractions

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6
Q

What does circular muscle do?

A

shortens ring of smooth muscle
- shortens DIAMETER

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7
Q

What does longitudinal muscle?

A

shortens in a longitudinal direction
- shortens LENGTH of SEGMENT

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8
Q

What are phasic contractions? Where does this occur?

A

periodic contractions followed by relaxation
- esophagus, gastric antrum, SI

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9
Q

What are tonic contractions? Where does this occur?

A

maintain a constant level of contraction or tone without regular relaxation
- upper region of stomach, lower esophagus, ileocecal, internal anal sphincters

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10
Q

Define slow wave of GIT.

A

unique to GI smooth muscle
oscillating repolarization and depolarization of membrane potential of smooth muscle cells

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11
Q

T/F: Slow waves may or may not bring membrane potential to threshold i.e. not always an AP

A

TRUE

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12
Q

More AP =

A

stronger contractions

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13
Q

The ______ has the highest contractions at 12/min, and the _______ has the lowest constrictions at 3/min.

A

duodenum
stomach

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14
Q

What is the origin of slow waves?

A

interstitial cells of cajal (myenteric plexus)
interstitial cells

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15
Q

What has depolarizations that occur simultaneously?

A

interstitial cells of cajal

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16
Q

What is the pacemaker for GI smooth muscle?

A

interstitial cells

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17
Q

Depolarization phase and maintenance of the plateau involves ________ in slow wave mechanisms.

A

opening of Ca2+ channels

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18
Q

Repolarization phase involves ________ in slow wave mechanisms.

A

opening of K+ channels

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19
Q

T/F: The frequency of slow waves are influenced by neural and hormonal output.

A

FALSE

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20
Q

List the 3 functions of mastication.

A

mix food with saliva to lubricate
reduce size of food particles
mix ingested carbohydrates with salivary amylase

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21
Q

What is the involuntary component of chewing?

A

mechanoreceptors in mouth relay to brainstem
- initiated by food in mouth

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22
Q

What is the voluntary component of chewing?

A

can override reflex chewing at any time

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23
Q

What is initiated voluntarily in the mouth?

A

swallowing (deglutition)

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24
Q

Where is the control for reflex swallowing located?

A

swallowing center in medulla
- receptors near pharynx detect and send information via vagus and glossopharyngeal nerves

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25
Q

What are the 3 phases in swallowing?

A

oral phase
pharyngeal phase
esophageal phase

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26
Q

Define oral phase.

A

voluntary at first then involuntary
- tongue forces bolus towards pharynx, involuntary swallowing takes over

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27
Q

Define pharyngeal phase.

A

involuntary, propel bolus from mouth through pharynx to esophagus in 4 steps

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28
Q

Explain the 1st step of the pharyngeal phase.

A

soft palate pulled up to narrow passage —> can’t move to nasopharynx

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29
Q

Explain the 2nd step of the pharyngeal phase.

A

epiglottis moves to cover the opening to the larynx
larynx moves up against epiglottis
- cover opening to trachea

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30
Q

Explain the 3rd step of the pharyngeal phase.

A

upper esophageal sphincter relaxes
food passes from pharynx to esophagus

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31
Q

Explain the 4th step of the pharyngeal phase.

A

peristaltic wave to propel bolus to sphincter

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32
Q

Define esophageal phase.

A

controlled by swallowing reflex AND enteric nervous system
- propels bolus to stomach

33
Q

What is the primary wave to push the bolus?

A

swallowing reflex closes upper esophageal sphincter

34
Q

What are the two waves in the esophageal phase?

A

primary peristaltic wave
secondary peristaltic wave (if needed)

35
Q

What is mediated by the ENS?

A

primary and secondary peristaltic waves in the esophageal phase

36
Q

T/F: The upper esophageal sphincter is closed unless bolus needs to pass through the esophagus.

A

TRUE

37
Q

The primary peristaltic contraction creates _______

A

high pressure area behind bolus

38
Q

When the peristaltic wave and bolus reach the lower esophageal sphincter, it _______, and is mediated by _______.

A

opens
vagus n. and VIP (neuromodulator)

39
Q

When bolus reaches the lower esophageal sphincter, there is __________ in the stomach, which causes pressure to _______.

A

receptive relaxation of upper region of stomach
pressure DECREASES

40
Q

The secondary peristaltic wave (if needed) _______

A

clears esophagus of any remaining food

41
Q

T/F: There is a pressure difference between upper and lower esophagus which is important.

A

TRUE

42
Q

What are the 3 components of gastric motility?

A

relaxation of orad region in stomach
contractions
gastric emptying

43
Q

What is hormonally regulated?

A

gastric emptying

44
Q

The caudad region is _______ for __________.

A

thick-walled
stronger contractions

45
Q

The stomach has ______ and _______ innervation.

A

external
internal

46
Q

What are the 3 muscle layers of the stomach?

A

outer longitudinal
middle circular
inner oblique

47
Q

Receptive relaxation of orad stomach is caused by the relaxation of lower esophageal sphincter, which will ______ pressure and ______ volume of stomach

A

decrease
increase

47
Q

What is the vasovagal reflex involved in? What limbs of the nerve?

A

receptive relaxation of the stomach
afferent and efferent

48
Q

Contractions begin in the ______

A

caudad region of stomach

49
Q

Waves begin in the ______

A

middle of body of stomach

50
Q

The waves become more ______ the closer you get to pylorus

A

rigorous

51
Q

During mixing and digestion, there may be retropulsion, which is ________

A

bolus propelled back, further reduction of particle size

52
Q

For slow waves, neural input and hormones can’t alter frequency, BUT they can alter ________

A

contraction strength

53
Q

Gastrin and motilin _______ force of contraction via _______

A

increase
PSNS

54
Q

Secretin and GIP _______ force of contraction via _______

A

decrease
SNS

55
Q

Migrating myoelectric complexes are mediated by _____ during fasting, to clear any remaining food.

A

motilin

56
Q

What are the goals of SI motility?

A

mix chyme with enzymes and secretions
expose nutrients to intestinal mucosa for absorption
propel chyme to LI

57
Q

Slow waves are more frequent in the ______

A

duodenum

58
Q

There is parasympathetic innervation in the small intestine via the _______, which will _______ contraction strength

A

vagus nerve
increase

59
Q

There is sympathetic innervation in the small intestine via the _______, which will _______ contraction strength

A

celiac and superior mesenteric ganglia
decrease

60
Q

What does the enteric nervous system coordinate in the small intestine?

A

segmentation
peristaltic contractions

61
Q

What are segmentation contractions

A

part of intestine that contractis to split digests and allow it to re-mix

62
Q

How does segmentation contractions mix chyme?

A

back and forth movement
NOT FORWARD

62
Q

For peristaltic contractions there is a ______ behind the bolus and _______ in front of bolus.

A

contraction behind
relaxation in front

63
Q

You need the _______ and ________ to work together during peristalsis.

A

circular muscle
longitudinal lmuscle

64
Q

What senses the bolus?

A

enterochromaffin cells

65
Q

What are enterochromaffin cells?

A

cells that sense the bolus
involved in peristaltic reflex for moving chyme

65
Q

What happens during vomiting?

A

information from vestibular system, back of throat, GIT, and chemoreceptor trigger zone in 4th ventricle
vomiiting center in medulla —> vomiting reflex

66
Q

What happens during 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

67
Q

Define retching

A

upper esophageal sphincter remain closed, lower open, contents return to stomach

68
Q

What sphincter opens to allows contents into cecum, then contracts to close?

A

ileocecal sphincter

69
Q

The colon in pigs forms a spiral colon where?

A

ascending colon

70
Q

What has no sigmoid colon?

A

dog, cat, horse

71
Q

Where do segmentation contractions occur in the large intestine? They are associated with _____

A

cecum
proximal colon
haustra

72
Q

Define haustra.

A

sac-like segments

73
Q

What has no haustra? What does?

A

NO: dogs, rats, carnivores, ruminants
YES: guinea pigs, rabbits, pigs, humans, monkeys, horses

74
Q

Define defecation

A

rectum fills and smooth muscle wall contracts
internal anal sphincter relaxes
external anal sphincter tonically contracted until defecation

75
Q

Define gastrocolic reflex. There is the afferent limb in the _______ and efferent limb in _______

A

distention of stomach increases motility of colon
afferent: stomach
efferent: colon

Veterinary Physiology (26 decks)

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