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GIGU > Motility of the GI > Flashcards

Motility of the GI Flashcards

1
Q

What is motility?

A

Contraction and relaxation of the walls and sphincters of the GI tract

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2
Q

What are the functional layers of the GI tract?

A

Mucosa
Submucosa
Muscularis externa
Serosa/Adventitia

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3
Q

What does the muscularis mucosae control?

A

Shape and surface area changes of the epithelium

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4
Q

What makes up the Enteric nervous system (intrinsic innervation of GI tract)?

A

Submucosal plexus of Meissner

Myenteric plexus of Auerbach

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5
Q

Which plexus mainly controls the GI movements?

A

Myenteric plexus of Auerbach

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6
Q

What are slow waves?

A

Depolarization and repolarization of membrane potential … NOT action potentials

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7
Q

Action potentials in the GI tract are under _____ and _____ control

A

Neural and Hormonal

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8
Q

What are phasic contractions?

A

Periodic contractions followed by a period of relaxation

- Seen in tissues that do most of the mixing and digesting = esophagus, stomach, SI

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9
Q

What are tonic contractions?

A

Constant level of contraction maintained

- ex. = sphincters such as the internal anal sphincter

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10
Q

How do you achieve a larger contraction in the GI system?

A

Increased number of action potentials on top of a slow wave

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11
Q

What stimuli can increase the slow wave amplitude and number of action potentials in the GI tract?

A

Stretch
Acetylcholine
Parasympathetics

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12
Q

What stimuli can decrease the slow wave amplitude in the GI tract?

A

Norepinephrine

Sympathetics

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13
Q

What generates and propagates slow waves?

A

Interstitial Cells of Cajal (ICC)

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14
Q

Describe the activity of the ICCs

A

ICCs spontaneously create slow waves which spread to other ICCs via gap junctions

  • This increases the probability of ca channels opening in smooth muscle cells
  • ICCs drive the frequency of contractions!
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15
Q

Swallowing is voluntary in the oral cavity and then it moves to involuntary reflex control. What controls the involuntary swallowing reflex in the pharynx and esophagus?

A

Medulla

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16
Q

The pharyngeal phase of swallowing propels food through what?

A

UES - upper esophageal sphincter

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17
Q

Describe the 2 types of peristaltic waves in the esophageal phase of swallowing

A
  • Primary peristaltic wave is the continuation of the pharyngeal peristalsis and is under medulla control
  • Secondary peristaltic wave occurs if the primary wave fails to empty esophageal contents and is under medulla AND ENS control
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18
Q

Which esophageal peristaltic wave can occur after a vagotomy? (vagus nerve removal)

A

Secondary peristaltic wave because it is under medulla and ENS control - so even without communication to medulla via vagus nerve, it can still occur

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19
Q

What is the pressure at and slightly below the UES?

A

High pressure

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20
Q

What is the pressure at and below the LES?

A

Low pressure

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21
Q

UES and LES are _____ except for when food is passing

A

Closed

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22
Q

Achalasia

A

INCREASED LES resting pressure

  • Causes difficulty swallowing and backflow of food in throat
    • can be caused by loss of NO/VIP or loss of innervation
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23
Q

GERD

A

DECREASED LES resting pressure

  • Causes acid backwash into esophagus and heartburn
    • can lead to Barrett’s esophagus
24
Q

What are the regions of the stomach based on motility?

A

Orad - towards top

Caudad - towards pylorus

25
Q

Describe the activity of the orad region of the stomach

A

Receptive relaxation = low pressure high volume

- Minimal contractile activity!!

26
Q

Describe the activity of the caudad region of the stomach

A

Mixing and digestion occur here

- Peristaltic contractions increase as the wave approaches the antrum = phase lag decreases

27
Q

Are most contents propelled backward in the stomach once they reach the bottom for further mixing and digestion?

A

Yes

28
Q

How is the rate of gastric emptying INCREASED?

A
  • Decrease distensible property of orad region
  • Increase for of peristaltic contractions in caudad region = parasymp, gastrin, motilin
  • Decrease tone of pylorus
  • Increase diameter of proximal duodenum
29
Q

How is the rate of gastric emptying DECREASED?

A
  • Increase distensibility of orad region - CCK
  • Decrease peristaltic contraction forces in caudad region - symp, secretin, GIP
  • Increase tone of pylorus
  • Decrease diameter of proximal duodenum
    ENTEROGASTRIC REFLEX
30
Q

What is the Enterogastric reflex?

A

Negative feedback from the duodenum to SLOW gastric emptying

– CCK, Secretin and GIP released!

31
Q

What does the duodenum release with the enterogastric reflex?

A

Secretin
CCK
GIP

32
Q

Gastroparesis

A

Slow emptying of gastric contents even without obstruction

- feeling full, loss of appetite and weight, nausea, vomiting

33
Q

With what disease is gastroparesis common?

A

Diabetes mellitus OR injury to the vagus nerve

34
Q

What does the MMC (migrating myoelectric complex) do?

A

Periodic bursting contractions in order to empty large particle of undigested residue

  • regulated by motilin
    • prevents small intestine bacterial overgrowth (SIBO)
35
Q

When does MMC occur?

A

In 90 minute intervals during FASTING

36
Q

What types of contractions does the small intestines have?

A 
Segmentation = back and forth movements
Peristaltic = wave like to propel forward
37
Q

Is slow wave activity always present even if there are no contractions occurring?

A

Yes

38
Q

In the small intestine, what hormone can stimulate contractions?

A

Serotonin

39
Q

What coordinates the vomiting reflex?

A

Medulla

40
Q

Describe the order of events of the vomiting reflex

A
  • reverse peristalsis in the small intestine
  • relaxation of stomach and pylorus
  • forced inspiration causes increase in abdominal pressure
  • LES relaxes
    = expulsion of contents
41
Q

The flow of contents from the SI to the LI is regulated at what juntion?

A

Ileocecal

42
Q

Describe how contents pass from the ileum to the cecum (colon)

A
  • Distention of ileum
  • Causes relaxation of sphincter
    = contents pass
43
Q

Describe how contents do NOT pass from the ileum to the cecum

A
  • Distention of colon
  • Causes contraction of sphincter
    = NO contents pass
44
Q

The internal and external anal sphincters are under different neural control. What controls the external anal sphincter?

A

Somatic Pudendal nerves

45
Q

What type of muscles are in the internal anal sphincter and external anal sphincter?

A

Internal anal sphincter = smooth muscle

External anal sphincter = skeletal muscle

46
Q

Describe the motility in the colon

A

Mass movements that occur 1-3 times a day

47
Q

What is the rectosphincteric reflex?

A

As the rectum fills with feces, the smooth muscle walls contract and the internal anal sphincter relaxes

48
Q

The frequency of slow waves DECREASES as you move towards what?

A

Ileum

49
Q

What stimuli inhibit the peristaltic contractions in the small intestine?

A 
Sympathetics
Epinephrine
Secretin 
Glucagon
NO/VIP
50
Q

What stimuli activate the peristaltic contractions in the small intestine?

A

Parasympathetics - Ach
Serotonin
Gastrin, motilin, insulin

51
Q

Parasympathetic innervation of the cecum, ascending colon and transverse colon?

A

Vagus nerve

52
Q

Parasympathetic innervation of the descending colon, sigmoid colon and rectum?

A

Pelvic splanchnic nerve (S2-S4)

53
Q

Levels of sympathetic innervation to the large intestine?

A

T10 - L2

54
Q

What ganglion contribute to the sympathetic innervation of the large intestine?

A

Superior mesenteric
Inferior mesenteric
Hypogastric plexus

55
Q

What is the innervation of the external anal sphincter?

A

Somatic pudendal nerve

GIGU (29 decks)

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