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Phys > Exam 4: Lecture 54: Gastrointestinal Motility > Flashcards

Exam 4: Lecture 54: Gastrointestinal Motility Flashcards

1
Q

What is the purpose of motility?

A
  • propel digesta through the tract
  • mixing
  • grinding
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2
Q

Circular muscle produces what type of contraction of the GIT?

A

Shortening of ring of smooth muscle - decrease the diameter of the segment

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3
Q

Longitudinal muscle produces what type of contraction?

A

Shortening in longitudinal direction

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4
Q

Phasic contractions produce what type of contraction?

A

Periodic contractions followed by relaxation

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5
Q

Tonic contractions produce what type of contraction?

A

They maintain a constant level of contraction without regular relaxation

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6
Q

Which part of the stomach is subject to tonic contraction?

A

Upper region of stomach - only relaxes when food drops from the esophagus.

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7
Q

What is the oscillating depolarization and repolarization of membrane potential of smooth muscle cells in the GIT?

A

Slow waves

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8
Q

T/F: The slow wave will always bring membrane potential to threshold.

A

False - they amy or may not bring it to threshold. Just because a slow wave is present does not mean an AP will be.

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9
Q

What is the frequency of the slow waves in the stomach?

A

~3/min

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10
Q

At which point in the GIT is the slow waves have the highest frequency?

A

Duodenum

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11
Q

Slow waves originate where?

A

Interstitial cells of Cajal - myenteric plexus

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12
Q

What cells are known as the pacemaker for the GI smooth muscle cells?

A

Interstitial cells of Cajal

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13
Q

To make a slow wave, what channels are opened to maintain the plateau?

A

Ca channels

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14
Q

Which channels are opened to start the repolarization of slow waves?

A

K+ channels

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15
Q

What are the three main functions of chewing?

A
  • Mix food with saliva to lubricate
  • Reduces size of food particles
  • Mixes ingested carbohydrates with salivary amylase
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16
Q

Involuntary/Voluntary component of chewing:
Initiated by food in mouth

A

involuntary

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17
Q

Involuntary/Voluntary component of chewing:
Can override reflex chewing

A

voluntary

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18
Q

Involuntary/Voluntary component of chewing:
Mechanoreceptors in mouth relay to brainstem

A

Involuntary

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19
Q

Reflex swallowing is controlled by what part of the brain?

A

Swallowing center in the medulla

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20
Q

Put the three phases of swallowing in order:
A. Pharyngeal phase
B. Oral phase
C. Esophageal phase

A

B, A, C

21
Q

Which phase of swallowing has voluntary properties?

A

Oral phase

22
Q

Which system(s) control the esophageal phase of chewing?

A

Swallowing reflex and enteric nervous system

23
Q

When during the oral phase, does the control become involuntary?

A

Once swallowing starts

24
Q

What is the first step of the pharyngeal phase of swallowing?

A

Soft palate is pulled up, narrows passage - bolus can’t move to the nasopharynx

25
Q

What is the second step of the pharyngeal phase of swallowing?

A

Epiglottis covers the opening to the larynx, larynx moves against epiglottis - covers the trachea

26
Q

What is the third step of the pharyngeal phase of swallowing?

A

Upper esophageal sphincter to open - food moves from pharynx to esophagus

27
Q

What is the last step of the pharyngeal phase of swallowing?

A

Peristaltic wave propels bolus

28
Q

In order for the lower esophageal sphincter to open what must occur?

A

A receptive relaxation of upper region in stomach

29
Q

The pressure is (higher/lower) in the thorax than the abdomen

A

Lower

30
Q

Gastric motility is comprised of what three components?

A
  • relaxation
  • contractions
  • gastric emptying
31
Q

What are the three muscle layers of the stomach?

A

Outer longitudinal
Middle circular
Inner oblique

32
Q

The relaxation of the lower esophageal sphincter has what effect on the orad stomach?

A

Relaxation

33
Q

What reflex is involved with receptive relaxation?

A

Vagovagal reflex

34
Q

Migrating myoelectric complexes are mediated by what hormone?

A

Motilin

35
Q

What are the three goals of SI motility?

A
  • Mix chyme with enzymes and secretions
  • Expose nutrients to intestinal mucosa for absorption
  • Propel chyme into LI
36
Q

Enteric nervous system coordinates __________________ and ________________ contractions.

A

segmentation; peristaltic

37
Q

The PSNS via vagus n. has what effect on the SI?

A

Increase contraction and strength

38
Q

The SNS via celiac and superior mesenteric ganglia have what effect on the SI?

A

Decrease contraction strength

39
Q

A contraction that has back and forth movement with no forward movement is called what?

A

Segmentation contractions

40
Q

Contractions that propels chyme towards the LI?

A

Peristaltic contractions

41
Q

Which hormone will decrease the force of contractions in the stomach?

A

Secretin

42
Q

What is the difference between emesis and retching?

A

Emesis has expulsion of stomach contents; in retching the upper esophageal sphincter is closed and nothing comes out.

43
Q

Which parts of the LI have segmentation contractions?

A

Cecum and proximal colon

44
Q

What are haustra?

A

sac-like segments - mirroring in a side to center fashion

45
Q

Which species does NOT have haustra?

A

Dogs, rats, carnivores, or ruminants

46
Q

Which species does have haustra?

A

guinea pigs, rabbits, pigs, humans, monkeys, and horses

47
Q

Describe the rectosphincteric reflex

A

Internal anal sphincter relaxes

48
Q

When the distention of the stomach increases the motility of the colon is called what?

A

Gastrocolic reflex

Phys (13 decks)

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