Gastric Motility

Question 1

Gastric motility between meals (interdigstive period)?

Answer 1

Clear undigested debris
Sloughed epithelial cells

Question 2

Gastric motility after a meal?

Answer 2

Adaptive relaxation = to accommodate ingested food
With little change in intra-gastric pressure (proximal)
Grinds and disperses the meal into fine particles (distal)

Question 3

The rate contents are delivered to duodenum optimizes what?

Answer 3

Mixing with pancreatic-billiary secretions
Maximal contact with brush boarder of enterocytes

Question 4

What causes reduction in proximal gastric tone?

Answer 4

Act of swallowing = stimulation of pharynx or esophagus
Relaxation occurs within 10s of swallowing

Reflex relaxation in response to gastric distension

Question 5

What mediates reflex relaxation in response to gastric distension?

Answer 5

Mechanoreceptors in gastric wall

Question 6

What is the difference between reflex and adaptive relaxation?

Answer 6

Adaptive relaxation does not require stimulation of pharynx or esophagus

Question 7

What is gastric adaptive relaxation mediated by?

Answer 7

Vago-vagal reflex arc
Volume

Question 8

What happens in a truncal or proximal gastric vagotomy?

Answer 8

Decreased gastric distensibility

Question 9

What triggers feedback relaxation?

Answer 9

Chyme in small intestine

Question 10

What does pyloric sphincter regulate?

Answer 10

Gastric emptying

Question 11

What does pyloric sphincter prevent?

Answer 11

Duodenal-gastric reflux

Question 12

What inhibitory reflexes regulate gastric emptying?

Answer 12

Gastro-gastric
Duodeno-gastric
Entero-gastric

Question 13

What neural control regulates gastric emptying?

Answer 13

Anger increases emptying

Pain, fear or depression decreases gastric emptying

Question 14

What hormonal control regulates gastric emptying?

Answer 14

Gastrin increases gastric emptying

CCK, secretin and GIP slows gastric emptying

Question 15

What foods cause a slower rate of gastric emptying?

Answer 15

Solid meal
Low volume meal
Fat = most potent
Proteins
Chyme w high acidity or osmotic pressure

Question 16

How are water and isotonic saline emptied?

Answer 16

Emptied rapidly
Half-life = 8-18 minute

Question 17

What are first-order kinetics and how are they altered?

Answer 17

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

Question 18

What causes delated gastric emptying, foodwise?

Answer 18

Nutrients
High caloric density

Question 19

What is maximum inhibition in gastric emptying?

Answer 19

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.

Question 20

What acts on small intestine osmoreceptors?

Answer 20

Carbohydrates and most amino acids

Question 21

What is the rate of emptying into duodenum?

Answer 21

200 kcal/hr

Question 22

What factors modify emptying of digestible solids?

Answer 22

Size in ingested food
Levels of fats, triglycerides, or monosaccharides
Liquids are emptied more rapidly than solids in a mixed meal

Question 23

What is abnormal gastric emptying?

Answer 23

Vomitting

Question 24

What is activated for projectile vomitting?

Answer 24

Vomit center in the medulla of the brainstem = activated by
Afferent fibres
Irritation due to injury
Increases in intracranial pressure

Question 25

What makes projectile vomiting different?

Answer 25

Not accompanied by nausea

Question 26

What is found in the brain stem, associated with projectile vomiting?

Answer 26

Chemoreceptor trigger zone

Question 27

How is chemoreceptor trigger zone activated?

Answer 27

Activated by afferent nerves originated from GIT when chemoreceptors in stomach or duodenum sense circulating vomitic agents

Question 28

Name vomitic agents

Answer 28

Apomorphine
Copper sulphate