Unit 4 Lecture 29

Question 1

What are the 3 phases of digestion?

Answer 1

1. Cephalic phase (anticipation)
2. Gastric phase (breakdown)
3. Intestinal phase (controlled release)

Question 2

What happens during the cephalic phase?

Answer 2

• prepares mouth and stomach for food

Question 3

How does the cephalic phase prepare the mouth and stomach for food?

Answer 3

Senses of food stimulate PARASYMPATHETIC nervous system to stimulate

1. salivation (facial and glossopharyngeal)
2. Gastric glands to secrete gastric juices (vagus)

Question 4

What are the 2 influences of the gastric phase?

Answer 4

Neural influence and endocrine (hormone) influences

Question 5

What are the neural influences over stomach activity?

Answer 5

• stretch receptors and chemoreceptors (pH) signal bolus entry
• vigorous peristalsis and gastric gland secretions
• chyme periodically released into the duodenum

Question 6

What are the endocrine (hormonal) influences over stomach activity?

Answer 6

• distention/ food in stomach -> G cells secrete gastrin -> increases gastric gland secretions, motility and causes pyloric sphincter to relax

Question 7

How is gastric emptying increased?

Answer 7

as bolus of food enters the stomach

• stimulates contractions of lower esophageal sphincter and relaxes pyloric sphincter

Question 8

What is the main function of the intestinal phase of digestion?

Answer 8

Controlled release of chyme

Question 9

What are the 2 influences of the intestinal phase?

Answer 9

Neural and endocrine (hormone ) influences

Question 10

What is the neural influence of the intestinal phase?

Answer 10

• Distension of the duodenum
• chemical contents of the chyme activates sympathetic nerves which slows gastric activity

Question 11

What reflex is associated with the neural influence of the intestinal phase of digestion?

Answer 11

Enterogastric reflex

Question 12

What is the endocrine influence of the intestinal phase?

Answer 12

• distension of duodenum and contents of chyme triggers hormonal release from enteroendocrine cells in duodenum

* remember small intestine cell, enteroendocrine cell secretes secretin and CCK

Question 13

What are the hormones released from the enteroendocrine cells in the duodenum and what do they do?

Answer 13

• secretin: decreases stomach secretions
• cholecystokinin (CCK): decreases stomach emptying

Question 14

What does secretin do?

Answer 14

stimulates secretion of sodium bicarbonate release

Question 15

What does CCK do?

Answer 15

stimulate secretion of digestive enzyme release