Lecture 29 Unit 4

Question 1

what are the three phases in regulation of digestion

Answer 1

• cephalic phase
• gastric phase
• intestinal phase

Question 2

what happens in the cephalic phase

Answer 2

• anticipation

- prepares the mouth and stomach for food

Question 3

what is stimulated in the cephalic phase

Answer 3

the cerebral cortex

Question 4

what happens in the cerebral cortex in the cephalic phase

Answer 4

sight, smell, taste, and thoughts of food stimulate the parasympathetic nervous system to stimulation salivation and gastric glands to secrete gastric juices

Question 5

what nerves increase salivation

Answer 5

facial and glossopharyngeal nerves

Question 6

what nerve stimulates gastric gland to secrete gastric juice

Answer 6

vagus nerve

Question 7

what happens in the gastric phase

Answer 7

breakdown of material

Question 8

in the gastric phase what are the neural influences over stomach activity

Answer 8

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

Question 9

in the gastric phase what are the endocrine influences over stomach activity

Answer 9

-distension and presence of food in stomach cause G cells to secrete gastrin into bloodstream; gastrin increases gastric gland secretions and motility and causes pyloric sphincter relaxation

Question 10

what happens in neural and hormonal regulation in gastric emptying

Answer 10

• distention of the stomach and presence of undigested contents increase the secretion of gastrin hormone and vagal nerve impulses
• stimulates contraction of the lower esophageal sphincter and the stomach as well as relaxation of the pyloric sphincter for emptying

Question 11

what happens in the intestinal phase

Answer 11

controlled release of chyme

Question 12

what happens when chyme enters duodenum

Answer 12

slows gastric activity and increases intestinal activity

Question 13

what are the neural influences in the intestinal phase

Answer 13

distension of the duodenum and chemical contents of the chyme activate sympathetic nerves which slow gastric activity (enterogastric reflex)

Question 14

what are the endocrine influences in the intestinal phase

Answer 14

distention of duodenum and contents of chyme trigger hormonal release from enteroendorcrine cells in the duodenum

Question 15

what are the hormones secreted in the intestinal phase and what do they do

Answer 15

• secretin-hormone decreases stomach secretions

- cholecystokinin (CCK)- decreases stomach emptying

Question 16

what does the enterogastric reflex do

Answer 16

regulates the amount of chyme released into the duodenum

Question 17

what is the entrogastric reflex initiated by

Answer 17

distension of duodenum and contents of the chyme

Question 18

how does the enterogastric reflex work

Answer 18

sensory impulses sent to the medulla inhibit parasympathetic stimulation of the stomach

Question 19

what are the hormones released by the enterogastric reflex and what do they do

Answer 19

cholecystokinin and secretin stimulate sympathetic impulses both inhibiting gastric emptying

Question 20

what does secretin do

Answer 20

acidity in intestine causes increased sodium bicarbonate release

Question 21

what does CCK do

Answer 21

fats and proteins cause increased digestive enzyme releasee

Question 22

what are the steps in regulation of pancreatic secretions by enteroendocrine cells

Answer 22

1. parasympathetic impulses along vagus nerves stimulate secretion of pancreatic enzymes
2. acidic chyme containing partially digested fats and proteins
3. CCK and secretin are released
4. stimulates secretion of pancreatic juices rich in bicarbonate ions and digestive enzymes

Question 23

what are the steps in the regulation of bile secretion by enteroendocrine cells

Answer 23

1. parasympathetic impulses along vagus nerves stimulate bile production in the liver
2. fatty acids and amino acids in chyme entering the duodenum stimulate secretion of CCK and secretin into blood
3. CCK causes contraction of gallbladder
4. secretin enhances flow of bile rile HCO3- from liver