Physiology: GI motility Flashcards
What is the rate of slow waves in the stomach?
The stomach has the lowest frequency of slow waves at 3 per minute
Where is the highest frequency of slow waves in the GI tract?
Duodenum (12 per minute)
Where do slow waves originate from?
interstitial cells of cajal
What causes slow wave depolarizations?
Influx of Ca
What causes slow wave repolarizations?
Efflux of K+
Where is the swallowing control center located and how does it function?
The swallowing control center is located in the medulla and it receives signals from the somatosensory receptors in the pharynx via CN IX and X
What is the process of LES relaxation?
Food approaches LES –> vasovagal reflex –> Release of VIP –> Relaxation of LES
What factors increased gastric contractions?
Parasympathetics, gastrin, motilin
What factors decrease gastric contractions?
Sympathetics, gastrin, GIP
How is gastric emptying regulated?
high fat –> increased CCK –> decreased gastric empyting
increased acidity in duodenum –> decreased gastric emptying
What are migrating myoelectric complexes?
Periodic contractions every 90 minutes during fasting that clear the GI tract of residual food/chyme
Where is vomiting regulated?
Medulla
What is the rectosphincteric reflex?
When the rectum is 25% full the internal anal sphincter will relax and there will be an urge to defecate.
What is the Gastrocolic reflex?
Distention of stomach by food –> Increased motility of colon
Afferent = parasympathetic Efferent = CCK and gastrin
What effect does osmolarity have on gastric emptying?
Isotonic solutions are emptied more rapidly
Hypotonic or hypertonic solutions are emptied more slowly.
