NME 2.18

Question 1

describe the membrane potentials for the interstitial cells of cajalin myenteric plexi?

Answer 1

• unstable membrane potentials

- keep fluctuating below threshold

Question 2

which extrinsic factor is excitatory?

Answer 2

• ACh

Question 3

which extrinsic factor is inhibitory?

Answer 3

• noradrenaline

Question 4

what happens to the small intestine during interdigestive phase?

Answer 4

• tonus activity
• spontaneous contraction of smooth muscle
• inherent mechanisms of tone and rhythmicity may be augmented by a background of transmitters such as ACh
• around 12 contraction/minute
• every fifth contraction is augmented by contraction of teh antrum due to transmission of slow waves crossing the sphincter
• prevent content from flowing back to duodenum

Question 5

what does the migrating myoelectric complex do during interdigestive phase?

Answer 5

• each cycle involves contraction of adjacent segments of small intestine
• last 10 minutes
• begin in stomach and migrate to proximal small intestine
• periodic sweep of contents towards colon
• helps to clean small intestine from residual food and secretion
• prevent migration of colonic bacteria into ileum

Question 6

what happens to the migrating myoelectric complex during interdigestive phase for fasting individuals?

Answer 6

• cycles of smooth muscle contractions with average frequency of around 1.5 hrs

Question 7

during digestive period is there peristaltic propulsion or non propulsive mixing or both?

Answer 7

both

Question 8

what is segmentation?

Answer 8

• contraction of rings of circular muscles along small intestine
• rings of muscle relax then adjacent segments contract
• result in mixing

Question 9

what happens to segmentation when chyme enters duodenum?

Answer 9

• increase in frequency and strength

Question 10

what does mixing do?

Answer 10

• alkaline pancreatic juice

- bile mix with acid

Question 11

what is minute rhythm?

Answer 11

• when segmentation occurs that last 1 minute followed by interval when contraction are weak or absent

Question 12

where does minute rhythm occur?

Answer 12

jejenum

Question 13

are there difference in large intestine during inter-digestive periods?

Answer 13

• no difference

Question 14

describe the bowel motility in large intestine?

Answer 14

• constant non propulsive churning through haustration and propulsive mass peristalsis 1 to 3 times a day

Question 15

what are the 4 components of defecation reflex?

Answer 15

• increase activity of sigmoid colon
• distention of rectum
• reflex contraction of rectum
• relaxation of internal and external anal sphincter

Question 16

what does defecation reflex cause?

Answer 16

• mass movement in the colon moving the faecal material into the rectum

Question 17

is defecation reflex under sympathetic or parasympathetic control?

Answer 17

parasympathetic

Question 18

what reflex is defecation reflex considered as?

Answer 18

spinal reflex and conscious control

Question 19

what influence the defecation reflex?

Answer 19

• mediated by impulses of internal nerve plexi
• refinforced by autonomic reflex transmitted by spinal cord
• influenced by signals from higher centres

Question 20

what happens during mass peristalsis at rectum?

Answer 20

• there will be rectal distention which cause relaxation of internal anal sphincter
• external anal sphincter is maintained and resist increase pressure by further contraction of pudendal nerve

Question 21

what pressure will there be urge to defecate?

Answer 21

18 mmHg

Question 22

what presssure does compulsive defecation occurs?

Answer 22

55 mmHg

Question 23

how is voluntary defecation initiated?

Answer 23

• voluntary relaxation of external anal sphincter

- abdominal muscular contraction

Question 24

what is hirschsprung disease?

Answer 24

• absence of submucosal and myenteric ENS ganglia

- internal anal sphincter does not relax after rectal distention

Question 25

what does hirschsprung disease cause?

Answer 25

• megacolon

- constipation