GI motility (Fan)

Question 1

What is the result of mixing food content with various secretions?

Answer 1

reduction in particle size, increased digestion, and enhanced absorption of nutrients

Question 2

What does aboral movement mean?

Answer 2

Towards the anus/away from the mouth (vomiting is the only exception to aboral movement)

Question 3

What is the purpose of phasic contractions?

Answer 3

Generate the force to move material along the tract

Question 4

What is the purpose of tonic contractions?

Answer 4

Normally occurs in sphincters. Creates resistance to movement

Question 5

Function of mastication (chewing)?

Answer 5

(1) reduce particle size (depends on consistency of food)
(2) mixing food with saliva to lubricate the mass and increase exposure to salivary amylase (carbohydrate digestion) and lingual lipase (lipid digestion)
(3) enhance stimulation of taste buds and other receptors in the oral cavity (increase salivation and appreciation of food)

Question 6

Oral phase of swallowing - involuntary or voluntary?

Answer 6

Both

Question 7

When does primary esophageal peristalsis begin?

Answer 7

After the contraction of the UES

Question 8

What is antral systole?

Answer 8

Simultaneous contraction of the terminal antrum and pylorus

Question 9

What is the result of antral systole?

Answer 9

(1) retrograde movement of chyme back into the stomach, leading to effective mixing
(2) shearing forces (grinding of luminal contents), which reduces partil size

Question 10

Personal factors that reduce the frequency of defecation?

Answer 10

1. diet low in insoluble fiber
2. insufficient fluid intake
3. excessive delay of defecation
4. narcotic drugs
5. physical inactivity
6. antibiotics
7. old age (improvable and hopefully correctable)

Question 11

What is the valsalva maneuver?

Answer 11

The Valsalva maneuver or Valsalva manoeuvre is performed by moderately forceful attempted exhalation against a closed airway, usually done by closing one’s mouth, pinching one’s nose shut while pressing out as if blowing up a balloon.
** Facilitates defecation **

Question 12

Describe resting conditions in the colon

Answer 12

rectum is empty and relaxed, the internal anal sphincter is contracted to near maximum tone and the EAS is near minimum tone

Question 13

During defecation, what innervation leads to movement of fecal material in the colon?

Answer 13

enteric and parasympathetic mediated reflexes lead to relaxaion of the internal anal sphincter and further colonic peristaltic contraction.

Question 14

What is special about the external anal sphincter?

Answer 14

under sympathetic and voluntary control

Question 15

how does morphine affect movement of chyme?

Answer 15

morphine increases resistance to movement of chyme/feces by stimulating generalized contractions. This reduces propulsive activity and can result in constipation.

Question 16

what affect does caster oil (ricinoleic acid) have on chyme movement?

Answer 16

decreases resistance to movement of chyme/feces by stimulating generalized contractions

Question 17

What are the three types of contraction occuring in the colon

Answer 17

1. mass movement (rare)
2. peistaltic activity - push stool aborally/to anus (occassional)
3. Segmenting nonperistaltic contactions (also known as haustral shuttling)

Question 18

What contractions occur in the small intestine?

Answer 18

1. segmental type contractions

Question 19

what is mass movement contraction?

Answer 19

sustain peristaltic wave

Question 20

significance of segmenting nonperistaltic contractions (haustral shuttling)?

Answer 20

slows fecal steam; ensures absorption of water and electrolytes

Question 21

How does inactivity affect bowel movements?

Answer 21

Physical inactivity for periods of time will inhibit mass movements (peristalsis). This may be rlated to the observation of constipation with bed rest or long plane trips

Question 22

What are the two set of pacemaker cells in the large intestine motility?

Answer 22

(1) ECA ggenerating cells at the submucosal border of circular muscle
(2) myenteric potential oscillation cells

Question 23

What are myenteric potential oscillation cells?

Answer 23

between circular and longitudinal cells. initiate additional low, irregular amplitude and high frequency chanes in the resting membrane potential. these changes are propagated for short distances. Haustra develop as a result of localized contractions.

Question 24

where is the cecum?

Answer 24

beginning of the large intestine

Question 25

what is the reflex for the ileo-cecal junction for ileal distension?

Answer 25

relaxation

Question 26

what is the reflex for the ileo-cecal junction for cecal distension?

Answer 26

increased contraction

Question 27

What are the functions of the ileocecal sphincter?

Answer 27

(1) to delay transit of chyme into the colon, allowing increased time for absorption
(2) to prevent bacterial overgrowth in the ileum