Gastric Motility Flashcards
Gastric motility between meals (interdigstive period)?
Clear undigested debris
Sloughed epithelial cells
Gastric motility after a meal?
Adaptive relaxation = to accommodate ingested food
With little change in intra-gastric pressure (proximal)
Grinds and disperses the meal into fine particles (distal)
The rate contents are delivered to duodenum optimizes what?
Mixing with pancreatic-billiary secretions
Maximal contact with brush boarder of enterocytes
What causes reduction in proximal gastric tone?
Act of swallowing = stimulation of pharynx or esophagus
Relaxation occurs within 10s of swallowing
Reflex relaxation in response to gastric distension
What mediates reflex relaxation in response to gastric distension?
Mechanoreceptors in gastric wall
What is the difference between reflex and adaptive relaxation?
Adaptive relaxation does not require stimulation of pharynx or esophagus
What is gastric adaptive relaxation mediated by?
Vago-vagal reflex arc
Volume
What happens in a truncal or proximal gastric vagotomy?
Decreased gastric distensibility
What triggers feedback relaxation?
Chyme in small intestine
What does pyloric sphincter regulate?
Gastric emptying
What does pyloric sphincter prevent?
Duodenal-gastric reflux
What inhibitory reflexes regulate gastric emptying?
Gastro-gastric
Duodeno-gastric
Entero-gastric
What neural control regulates gastric emptying?
Anger increases emptying
Pain, fear or depression decreases gastric emptying
What hormonal control regulates gastric emptying?
Gastrin increases gastric emptying
CCK, secretin and GIP slows gastric emptying
What foods cause a slower rate of gastric emptying?
Solid meal
Low volume meal
Fat = most potent
Proteins
Chyme w high acidity or osmotic pressure
How are water and isotonic saline emptied?
Emptied rapidly
Half-life = 8-18 minute
What are first-order kinetics and how are they altered?
300mL bolus of saline emptied 2x faster than 150mL = due to 1st order kinetics
Feedback from small intestine alters 1st order kinetics
300mL 11% glucose = 150mL 11% glucose
What causes delated gastric emptying, foodwise?
Nutrients
High caloric density
What is maximum inhibition in gastric emptying?
Maximum inhibition in gastric emptying refers to the greatest degree to which the emptying of gastric contents into the small intestine is slowed or delayed.
What acts on small intestine osmoreceptors?
Carbohydrates and most amino acids
What is the rate of emptying into duodenum?
200 kcal/hr
What factors modify emptying of digestible solids?
Size in ingested food
Levels of fats, triglycerides, or monosaccharides
Liquids are emptied more rapidly than solids in a mixed meal
What is abnormal gastric emptying?
Vomitting
What is activated for projectile vomitting?
Vomit center in the medulla of the brainstem = activated by
Afferent fibres
Irritation due to injury
Increases in intracranial pressure
What makes projectile vomiting different?
Not accompanied by nausea
What is found in the brain stem, associated with projectile vomiting?
Chemoreceptor trigger zone
How is chemoreceptor trigger zone activated?
Activated by afferent nerves originated from GIT when chemoreceptors in stomach or duodenum sense circulating vomitic agents
Name vomitic agents
Apomorphine
Copper sulphate
