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HDSO Digestion System > Physiology -- Intestinal Motility > Flashcards

Physiology -- Intestinal Motility Flashcards

1
Q

4 functions of the upper small intestine

A
  • Neutralization
  • Osmotic equilibration
  • Digestion
  • Absorption
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2
Q

2 motor activities of the small intestine

A
  • Effective mixing
  • Slow propulsion
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3
Q

Time for food to be propulsed through the small intestine

A

2 - 4 hours

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4
Q

5 characeristics of intestinal BER

Note the wave form

A
  • Constantly present (not initiative of contractions)
  • Propagated from cell to cell
  • Constant frequency for a given region
  • Detectable in both longitudinal and circular muscle
  • Unknown origin, but probably ICC
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5
Q

7 characteristics of intestinal ERA

A
  • Intermittent
  • Phase-locked to BER
  • Stimulus = ACh and stretch
  • Ca++ independent
  • In longitudinal and circular fibers
  • Cell to cell propagation
  • # spikes/burst proportional to magnitude of stimulus
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6
Q

Describe how the action potential propagates through the intestinal muscle

A

When an AP is elicited in intestinal muscle fibre, it travels (via gap-junctions) and activates adjacent fibres which contract (synchronously along circumference and sequentially along the longitudinal axis)

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7
Q

Describe the intrinsic frequency of intestinal BER

A

Depends on the cells (i.e. the portion of the small intestine) –> decreases distally

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8
Q

Compare the coupling of intestinal cells versus stomach in terms of BER

A

Not as good

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9
Q

Compare 3 aspects of proximal SI BER versus distal SI BER and what these mean

A
  • f of BER is greater in proximal
  • Excitability of smooth muscle is great in proximal
  • Thickness of smooth muscles is greater in proximal

THEREFORE, both frequency and amplitude of contraction is greater in proximal SI

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10
Q

Most common type of contractile activity

A

Sementation

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11
Q

Myogenic properties of segmentation in SI

A
  • Stimulus = distension
  • Only circular muscle involved
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12
Q

ENS properties of segmentation in SI

A
  • Organizes over longer distances
  • Pattern-generated circuity –> alternating segments become disinhibited and therefore capable of contracting
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13
Q

Modulatory factors for segmentation in SI

A

ANS (vagus, sympathetic) and hormones

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14
Q

Function of segmentation in SI

A

Mixing

Slow propulsion

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15
Q

Pressure produced by segmentation in SI

A

5 - 10 mmHg

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16
Q

Length of segments in SI segmentation

A

1 - 5 cm

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17
Q

Define slow net aboral movement

A

Slowness of meal movement through SI (2-4 to 6 hours)

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18
Q

Describe peristalsis in the intestine

A
  • Infrequent, irregular
  • Weak, shallow
  • Travels for short (a few cm) distances only
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19
Q

What controls intestinal peristalsis

A
  • Local reflexes (integrity of ENS essential)
  • Modulated by ANS and hormones
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20
Q

Descibre intestinal peristalsis relative to bolus position (Law of the Intestine)

A

Radial stretch –> receptors –> neural nediation–>

Behind bolus:

  • Circular muscle contracts
  • Longitudinal muscle relaxes

Ahead of bolus

  • Circular muscle relaxes
  • Longitudinal muscle contracts
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21
Q

Describe the circuitry involved in bolus movement by peristalsis according to the Law of the Intestine

A
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22
Q

Describe the pressure changes in the ileocecal sphincter based on the location of distension

A
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23
Q

Normal state of ileocecal sphincter and why

A

High pressure state (+40 mmHg) = closed

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24
Q

Effect of circular muscle contracting in colon

A

Production of haustra

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25
Q

Volume of output from small intestine

26
Q

Volume of output from colon

27
Q

Function of colon

A
  • Mixing
  • Propulsion
  • Storage
28
Q

Purpose of mixing in colon

A

Promotion of absorption of water and ions

29
Q

Rate of propulsion through colon

A

50 - 60 hours

30
Q

Location of functions in colon

31
Q

Describe the BER of the colon

32
Q

Motor activities of the colon

A

Segmentation and peristalsis (very sluggish)

33
Q

Rate of contraction in ascending colon

A

5 - 12 per min

34
Q

Rate of contraction in transverse colon

A

8 - 12 per min

35
Q

Rate of contraction in descending colon

A

6 - 8 per min

36
Q

Rate of contraction in sigmoid colon

A

17 per min

37
Q

3 colic reflexes

A
  • Gastroileal reflex
  • Gastrocolic reflex
  • Ileocolic reflex
38
Q

Describe the organization of GI motility during the interdigestive period

A

Intense pattern of cyclic myoelectric activity

  • Recurring at regular intervals (~90 min)
  • Moving sequentially over stomach, small intestine, up to distal ileum (2 - 10 cm/min)
39
Q

Describe phase I of the migrating myoelectric complex

A
  • 60 min duration
  • No spike potentials
  • No contractions
40
Q

Describe phase 2 of the migrating myoelectric complex

A
  • 20 min duration
  • Irregular spike potentials and contractions
41
Q

Describe phase 3 of the migrating myoelectric complex

A
  • 10 min duration
  • Regular spike potentials and contractions
42
Q

Propagation rate of the MMC

43
Q

Describe the onset and progression of MMC

44
Q

How is the MMC initiated?

A

ENS essential: periodic activation of pattern-generating circuitry

Unsure of role of CNS< ANS and gut peptides

45
Q

How is the MMC propagated?

A

ENS with modulation via ANS and gut peptides

46
Q

How is the MMC interrupted?

A

Intake of a new meal

47
Q

2 functions of MMC functions

A
  • “Housekeeping” (accompanied by secretory migrating complex)
  • Gastric emptying of large non-digestible particles
48
Q

Purpose of housekeeping by MMC

A

Prevention of bacterial overgrowth

49
Q

State of pyloric sphincter during MMC

A

Open during phase II (reason why large non-digestible particles can pass)

50
Q

Bristol Stool Chart type 1

A

Separated hard lumps, like nuts (hard to pass)

51
Q

Bristol Stool Chart type 2

A

Sausage-shaped but lumpy

52
Q

Bristol Stool chart type 3

A

Like a sausage, but with cracks on its surface

53
Q

Bristol Stool Chart type 4

A

Like a sausage or snake, smooth and soft

54
Q

Bristol Stool Chart type 5

A

Soft with clear-cut edges (passed easily)

55
Q

Bristol Stool Chart type 6

A

Fluffy pieces with ragged edges; a mushy stool

56
Q

Bristol Stool Chart type 7

A

Watery, no solid pieces (entirely liquid)

57
Q

Predominant gender affected by irritable bowel syndrome

58
Q

Percent of North America affected by IBS

A

At least 20%

59
Q

3 classic symptoms of IBS

A
  • Chronic abdominal pain or discomfort associated with chaotic bowel mobility
  • Heightened visceral sensitivity
  • Constopation dominant IBS, diarrhea dominant
60
Q

Rome III Criteria for IBS

A

At least 12 weeks or more, with onset of at least 6 months previously of recurrent abdominal pain or discomfort associated with two or more of the following:

  • Improvement with defecation
  • Onset associated with a change in frequency of stool
  • Onset associated with a change in form (appearance) of stool
61
Q

3 pathogenic possibilites for IBS

A
  • Post-infectious IBS
  • Interstitial cells of Cajal issue
  • Serotonin pathway issue

HDSO Digestion System (29 decks)

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