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PHGY-210 > GIT - Lecture 5 > Flashcards

GIT - Lecture 5 Flashcards

1
Q

What is vomiting?

A

the emptying of the contents of the upper GIT

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2
Q

What does vomiting result from?

A

an increase in intraabdominal pressure

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3
Q

What increases intraabdominal pressure during vomiting?

A

the action of the diaphragm and the abdominal muscles

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4
Q

Is the GIT passive or active during vomiting?

A

passive

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5
Q

What happens to the proximal stomach and above before vomiting?

A

they relax

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6
Q

What happens to the upper duodenum and distal stomach before vomiting?

A

they contract

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7
Q

What happens to the diaphragm and the abdominal muscles during vomiting?

A

diaphragm: lowers
abdominal muscles: contract

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8
Q

During vomiting, the intraabdominal pressure overcomes ___.

A

LES

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9
Q

What is the vomiting centre near?

A

fourth ventricle

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10
Q

What activates the vomiting centre?

A

afferents

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11
Q

What can send afferents to the vomiting centre? (6)

A

 Pharyngeal Stimulation
 GIT or urogenital distension
 Pain, cardiac ischemia
 Biochemical disequilibrium
 Vestibular Signals
 Psychogenic Factors

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12
Q

What does the vomiting centre activate once it has activated?

A

efferents

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13
Q

What are the 4 efferent outputs of the vomiting centre?

A
  1. widespread autonomic discharge
  2. nausea
  3. retching
  4. emesis
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14
Q

Why do you feel cold/sweaty when you want to vomit?

A

because the efferents are involved in both the sympathetic and the parasympathetic system which are imbalanced

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15
Q

What do the efferents lead to in the parasympathetic and the sympathetic activities?

A

an imbalance

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16
Q

What actions precede and accompany vomiting?

A

sweating, vasoconstriction, salivation, alternating bradycardia, tachycardia

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17
Q

What does emesis do to the upper GI tract + pyloric antrum and duodenum?

A

upper GI tract: relaxation
pyloric antrum and duodenum: spasm

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18
Q

What does emesis do to the abdominal muscles and diaphragm?

A

contraction

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19
Q

What is the second region in the brain that can lead to vomiting?

A

chemoreceptor trigger zone

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20
Q

Is the chemoreceptor trigger zone inside or outside the blood-brain barrier?

A

outside

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21
Q

What can act on the chemoreceptor trigger zone within the medulla?

A

circulating emetic agents

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22
Q

Where does the CTZ send signals to?

A

the vomiting centre

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23
Q

Why is it important that the CTZ is outside the blood-brain barrier?

A

so that it can be activated by the circulating emetic agents

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24
Q

What are the 3 stages of vomiting?

A
  1. nausea
  2. retching
  3. emesis
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25
Q

What is nausea?

A

a psychic experience

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26
Q

What is retching?

A

abrupt, uncoordinated respiratory movements with glottis closed

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27
Q

What is emesis?

A

actual expulsion of contents of upper GIT

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28
Q

What is the process of vomiting?

A

the individual takes a deep breath, glottis closes, abdominal
muscles contract, exerting pressure on gastric contents

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29
Q

What happens to the thoracic pressure and diaphragm once emesis is completed?

A

thoracic pressures: negative -> positive
diaphragm: displaced upwards

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30
Q

Where does most digestion and all absorption of nutrients occur?

A

the small intestine

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31
Q

What are the 3 regions of the small intestine?

A
  • duodenum
  • jejunum
  • ileum
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32
Q

What are the 4 functions of the upper small intestine (mostly duodenum)?

A
  1. neutralization
  2. osmotic equilibration
  3. digestion
  4. absorption
33
Q

Why does chyme entering the stomach need to be rapidly neutralized?

A

because it is highly acidic

34
Q

Which mucosa is well protected from acid? Which one isn’t?

A

stomach mucosa is, small intestine isn’t

35
Q

When will chyme be isotonic?

A

by the time it leaves the duodenum

36
Q

What are the 2 motor activities of the small intestine?

A
  • effective mixing
  • slow propulsion
37
Q

How long can an eaten meal be in the small intestine for?

A

2-6 hours

38
Q

What are the intestinal contractions governed by?

A

electrical characteristics of smooth muscle

39
Q

What is frequency of the small intestine governed by?

A

BER (ECA)

40
Q

What are the spikes of the small intestine initiated by?

A

stretch or ACh

41
Q

What is the amplitude of contraction of the small intestine related to?

A

the number of spikes/burst of ERA

42
Q

What does intrinsic frequency of BER vary in the small intestine?

A

different cells of the small intestine

43
Q

What happens to the frequency of BER from proximal to distal intestine?

A

it declines

44
Q

What is present along the entire length of the SI?

A

pacemaker cells

45
Q

What is the frequency of BER in the duodenum compared to the ileum?

A

duodenum: 12 cycles/min
ileum: 8 cycles/min

46
Q

What do the contractions of the small intestine contribute to?

A

the foreward movement of contents

47
Q

Both the frequency and the amplitude of muscle contractions are ___ in the proximal small intestine.

A

greater

48
Q

Does the maximal contractile activity in the small intestine exceed the BER frequency of that gut segment?

A

no, it cannot

49
Q

What is the most common type of contractile activity in the SI after a meal?

A

segmentation

50
Q

What initiates segmentation in the SI?

A

myogenic response to distention

51
Q

What coordinates and organizes contraction over a length of small intestine in the GI?

A

ENS

52
Q

What can modulate what happens at the musculature of the SI?

A

ANS and hormones

53
Q

What happens to parasympathetic and sympathetic in the SI after a meal?

A

parasympathetic: increases
sympathetic: decreases

54
Q

What is the function of segmentation?

A

mixing and slow propulsion

55
Q

How does mixing cause slow propulsion?

A

since there are more contractions and stronger contractions
proximally, there will be a slow, net aboral propulsion of contents

56
Q

Proximal:
___ contractions

A

more + stronger

57
Q

Distal:
___ contractions

A

fewer + weaker

58
Q

How is peristalsis in the small intestine characterized?

A
  • infrequent, irregular
  • weak, shallow
  • travels for short distances
59
Q

What is intestinal peristalsis mediated by?

A

a series of local reflexes

60
Q

Intestinal peristalsis involves interactions of which 2 muscles?

A

longitudinal and circular

61
Q

Maximum frequency ___ exceed frequency of BER.

A

cannot

62
Q

What is intestinal peristalsis modulated by (2)?

A

ANS and hormones

63
Q

What is the pathway of the “Law of the Intestine”?

A

radial stretch -> receptors -> neurally mediated

64
Q

When does contraction of longitudinal muscle and relaxation of circular muscle occur?

A

ahead of the bolus

65
Q

What is found between the ileum and the colon?

A

ileocecal sphincter

66
Q

What is the first portion of the colon called?

A

cecum

67
Q

Is the ileocecal sphincter open or closed normally?

A

closed

68
Q

What is the colon contractile activity similar to?

A

SI but slower and more sluggish/irregular

69
Q

What does the colon absorb?

A

water and some ions

70
Q

How much water enters the ileocecal sphincter per day?

A

1500 mL

71
Q

How much water is expelled from the colon each day?

A

200 mL

72
Q

What are the functions of the colon?

A
  1. mixing
  2. propulsion
  3. storage
73
Q

What is the rate of colon propulsion?

A

slow

74
Q

How long does the colon take to convert chyme to feces?

A

50-60 hours

75
Q

What is governed by irregular BER in the colon?

A

segmentation and peristalsis

76
Q

How and when does the large intestine empty its contents?

A

2-3x a day, corresponding to the intake of a new meal

77
Q

Why does the large intestine empty its contents?

A

because there is increased activity in the colon and distal SI

78
Q

What are the 3 reflexes produces after the intake of a meal?

A
  • gastroileal reflex
  • gastrocolic reflex
  • ileocolic reflex

PHGY-210 (36 decks)

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