Motility of GI tract Flashcards
what types of smooth muscle contraction aid in digestion?
tonic
phasic
Which parts of the digestive tract utilize phasic?
esophagus
gastric body and antum
small intestine
colon
what are 4 types of phasic contractions
- peristalisis
- mixing segmenting contractions
- migrating motility complex
- colonic mass movement
When do peristalic contractions (via pacemaker cells) occur in stomach, intestine, and colon?
when chyme is present
True or False. The frequency of peristalic contractions is 20/min.
False 3/min
what is the force of mixing contractions regulated by?
parasympathetic and sympathetic activity
where do mixing contractions occur?
small and large intestine
when do migrating motility contractions start and stop?
stop – when next meal enters stomach
start – when stomach almost empty
purpose of migrating motility contractions?
load chyme from last meal into proximal colon
controled by hormone— motilin
What determines rate of segmenting and peristalic contractions? Is it mechanical or electrical
slow waves.
electrical
True or False. Gastric peristaltic waves involve SLOW contraction of inner circular muscle and RAPID contraction of outer longitudinal muscle
False: vice versa
What factors increase gastric muscle excitibility?
- vagal (parasympathetic) stimulation of ENS
- excitory neurotransmitters
- gastrin
What factors decrease gastric muscle excitibity?
- enterogastrons (secretin, CCK)
- sympathetic innervation
- inhibitory neurotransmitters
what cause the release of enterogastrons?
increased (in the duodenum)
fat, acidity, amino acids
hypertonicity
distension
how long does it take to digest and absorb a meal?
3 - 8 hours
what is the exact mechanism that allows chyme to advance into colon?
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.
What type of contractions occur in the colon
sustained peristaltic contractions
Defecation reflex
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
symptoms of hirschsprung’s disease in infants
constipation
megacolon
narrow segment of colon in the rectum.
what is lacking in hirschsprung’s disease?
ganglion cells in the submucosal and myenteric plexus.
What is a consequence of poor motility?
greater Na and H2O absorption im transverse colon leading to constipation
excess motility results in less absorption = diarrhea
