15 Gut, ENS, Gastrointestinal Motility Flashcards

1
Q

Nutrient Absorption chiefly occurs where?

A

small intestine (with less in the colon)

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2
Q

What % immune function of the body is in the gut?

A

60-70%

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3
Q

Gut Endocrine control includes what 4 substances?

A
  • Gastrin from G cells
  • CCK from I cells
  • Secretin from S cells
  • Motilin
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4
Q

Name the 4 non-peptide transmitters in the gut?

A
  • ACh
  • Histamine
  • NO
  • Norepinephrine
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5
Q

T/F the ENS (enteric nervous sys.) can function w/o the CNS?

A

T

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6
Q

ENS has how many neurons?

A

100 million (same # as spinal cord)

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7
Q

IPAN’s do what?

A

gut afferents to the MEDULLA (& reflex loops ex. vagovagoal), responding to chemicals, stretch, mechanical stimuli

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8
Q

Gut interneurons connect what?

A

IPANs w/ motor neurons

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9
Q

What 3 kinds of motor neurons are found in the gut?

A
  • Muscle
  • Secretomotor
  • Vasodilator
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10
Q

Parasympathetics: vagus supplies the whole gut except what?

A
  • Pharynx

- Distal third of colon (done by splanchnics)

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11
Q

Pharyngeal function is what CN’s?

A

5,9,10,12

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12
Q

T/F sympathetic nerves directly innervate gut cells?

A

T. (ALSO indirectly innervate via ENS neurons)

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13
Q

Gut CCK affects the brain how?

A

Induces satiety

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14
Q

Syncytium is what?

A

Layers of intestinal smooth muscle connected by gap junctions so that the whole layer activates simultaneously

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15
Q

T/F muscularis mucosa assists with motility?

A

F. Only helps w/ secretion & churning, not travel of food thru the bowel.

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16
Q

A chunk of food gets stuck in your intestine, causing stretch. What happens to the gut proximal and distal to this stretch?

A
  • Proximal: Constricts

- Distal: Relaxes

17
Q

Gut smooth muscle, once depolarized, constricts by what mechanism?

A
  • voltage-dependent Ca channels &

- Release of internal Ca via G-protein cascade

18
Q

What is gut slow-wave depolarization?

A

aboral (toward the anus) direction of depolarization. This is governed by ENS & has a dif. frequency in dif. parts of gut.

19
Q

What are Interstitial Cells of Cajal?

A

Provide pacemaker activity for slow-wave gut depolarizations

20
Q

Mixing/churning is don’t by what kind of contractions?

A

Segmental/phasic (not propagated downstream)

21
Q

Food bolus proximal to a sphincter causes the sphincter to?

A

Open. (bolus distal to sphincter does the opposite)

22
Q

Sphincters have what 2 functions?

A
  • prevent retrograde flow

- provide reservoir function

23
Q

Describe the phases of small bowel motility while fasting?

A

“Migrating Motor Complex (MMC)” phases:
1-quiescent
2-brief intermittent contractions, SOME of which propagate downstream
3-brief high-amplitude contractions that propagate downstream

24
Q

Describe small bowel motility after feeding?

A

Strong, irregular contractions similar to phase 2 of fasting (SOME propagate, some not)

25
Q

List functions of the colon?

A
  • Fluid/electrolyte absorption
  • Short chain fatty acid absorption (these are fermented carbs)
  • Reservoir & defecation
26
Q

Describe colon motility pattern?

A
  • segmental contractions for mixing create haustra
  • Mass peristalsis (HAPC’s, high-amplitude propagating contractions) occur several times per day, often stimulated by food in the stomach. This pushes stool into the rectum.
27
Q

When no stool is in rectum, describe anal canal & sphincter

A

both are closed

28
Q

When stool arrives in rectum, what happens?

A

stretching->
reflex relaxation internal anal sphincter & sense of needing to poo->
voluntary relaxation of external anal sphincter + contraction of pelvic floor muscles

29
Q

Describe Hirschsprung’s disease?

A
  • Absence of Meissner’s and Auerbach’s plexuses
  • Absence of rectum stretch reflex if at rectal level (internal anal sphincter doesn’t dilate)
  • Diseased area remains normal due to tonic contraction, while upstream bowel gets very dilated
30
Q

What is Crohn’s disease?

A

inflammatory bowel disease

31
Q

If colon bacteria get into the small intestine (maybe due to a resected ileocecal sphincter), what occurs?

A

Gas

32
Q

Principal neurotransmitter of the gut is?

A

ACh