Motility of GI tract

Question 1

what types of smooth muscle contraction aid in digestion?

Answer 1

tonic

phasic

Question 2

Which parts of the digestive tract utilize phasic?

Answer 2

esophagus
gastric body and antum
small intestine
colon

Question 3

what are 4 types of phasic contractions

Answer 3

1. peristalisis
2. mixing segmenting contractions
3. migrating motility complex
4. colonic mass movement

Question 4

When do peristalic contractions (via pacemaker cells) occur in stomach, intestine, and colon?

Answer 4

when chyme is present

Question 5

True or False. The frequency of peristalic contractions is 20/min.

Answer 5

False 3/min

Question 6

what is the force of mixing contractions regulated by?

Answer 6

parasympathetic and sympathetic activity

Question 7

where do mixing contractions occur?

Answer 7

small and large intestine

Question 8

when do migrating motility contractions start and stop?

Answer 8

stop – when next meal enters stomach

start – when stomach almost empty

Question 9

purpose of migrating motility contractions?

Answer 9

load chyme from last meal into proximal colon

controled by hormone— motilin

Question 10

What determines rate of segmenting and peristalic contractions? Is it mechanical or electrical

Answer 10

slow waves.

electrical

Question 11

True or False. Gastric peristaltic waves involve SLOW contraction of inner circular muscle and RAPID contraction of outer longitudinal muscle

Answer 11

False: vice versa

Question 12

What factors increase gastric muscle excitibility?

Answer 12

1. vagal (parasympathetic) stimulation of ENS
2. excitory neurotransmitters
3. gastrin

Question 13

What factors decrease gastric muscle excitibity?

Answer 13

1. enterogastrons (secretin, CCK)
2. sympathetic innervation
3. inhibitory neurotransmitters

Question 14

what cause the release of enterogastrons?

Answer 14

increased (in the duodenum)
fat, acidity, amino acids

hypertonicity

distension

Question 15

how long does it take to digest and absorb a meal?

Answer 15

3 - 8 hours

Question 16

what is the exact mechanism that allows chyme to advance into colon?

Answer 16

gastroileal reflex…..
when the stomach fills with a new meal the ileum contracts and ileocecal sphincter relaxes, advancing chyme into the colon. Then, contact of chyme with the colonic wall reflexly causes the ileocecal sphincter to contract. This reflex serves to clear chyme from small intestine, advancing it into the colon.

Question 17

What type of contractions occur in the colon

Answer 17

sustained peristaltic contractions

Question 18

Defecation reflex

Answer 18

feces enter rectum, expand walls, excites ENS which contracts smooth muscle of descending and sigmoid colon and rectum. The internal anal sphinchter relaxes. The external anal sphincter is under voluntary control , hence either relaxes to allow defecation, or remains contracted

Question 19

symptoms of hirschsprung’s disease in infants

Answer 19

constipation
megacolon
narrow segment of colon in the rectum.

Question 20

what is lacking in hirschsprung’s disease?

Answer 20

ganglion cells in the submucosal and myenteric plexus.

Question 21

What is a consequence of poor motility?

Answer 21

greater Na and H2O absorption im transverse colon leading to constipation

excess motility results in less absorption = diarrhea