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Block D - Digestion and Metabolism > 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
Volume of output from small intestine
1500 mL
26
Volume of output from colon
200 mL
27
Function of colon
* Mixing * Propulsion * Storage
28
Purpose of mixing in colon
Promotion of absorption of water and ions
29
Rate of propulsion through colon
50 - 60 hours
30
Location of functions in colon
31
Describe the BER of the colon
Irregular
32
Motor activities of the colon
Segmentation and peristalsis (very sluggish)
33
Rate of contraction in ascending colon
5 - 12 per min
34
Rate of contraction in transverse colon
8 - 12 per min
35
Rate of contraction in descending colon
6 - 8 per min
36
Rate of contraction in sigmoid colon
17 per min
37
3 colic reflexes
* Gastroileal reflex * Gastrocolic reflex * Ileocolic reflex
38
Describe the organization of GI motility during the interdigestive period
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
Describe phase I of the migrating myoelectric complex
* 60 min duration * No spike potentials * No contractions
40
Describe phase 2 of the migrating myoelectric complex
* 20 min duration * Irregular spike potentials and contractions
41
Describe phase 3 of the migrating myoelectric complex
* 10 min duration * Regular spike potentials and contractions
42
Propagation rate of the MMC
5 cm/min
43
Describe the onset and progression of MMC
44
How is the MMC initiated?
ENS essential: periodic activation of pattern-generating circuitry Unsure of role of CNS\< ANS and gut peptides
45
How is the MMC propagated?
ENS with modulation via ANS and gut peptides
46
How is the MMC interrupted?
Intake of a new meal
47
2 functions of MMC functions
* "Housekeeping" (accompanied by secretory migrating complex) * Gastric emptying of large non-digestible particles
48
Purpose of housekeeping by MMC
Prevention of bacterial overgrowth
49
State of pyloric sphincter during MMC
Open during phase II (reason why large non-digestible particles can pass)
50
Bristol Stool Chart type 1
Separated hard lumps, like nuts (hard to pass)
51
Bristol Stool Chart type 2
Sausage-shaped but lumpy
52
Bristol Stool chart type 3
Like a sausage, but with cracks on its surface
53
Bristol Stool Chart type 4
Like a sausage or snake, smooth and soft
54
Bristol Stool Chart type 5
Soft with clear-cut edges (passed easily)
55
Bristol Stool Chart type 6
Fluffy pieces with ragged edges; a mushy stool
56
Bristol Stool Chart type 7
Watery, no solid pieces (entirely liquid)
57
Predominant gender affected by irritable bowel syndrome
Females
58
Percent of North America affected by IBS
At least 20%
59
3 classic symptoms of IBS
* Chronic abdominal pain or discomfort associated with chaotic bowel mobility * Heightened visceral sensitivity * Constopation dominant IBS, diarrhea dominant
60
Rome III Criteria for IBS
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
3 pathogenic possibilites for IBS
* Post-infectious IBS * Interstitial cells of Cajal issue * Serotonin pathway issue

Block D - Digestion and Metabolism (29 decks)

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