Lecture 39 11/16/23

Question 1

What are the characteristics of gastrointestinal hormones?

Answer 1

-produced by enteroendocrine cells
-released by physiologic stimuli
-circulate in blood
-bind to receptors at distant sites
-evoke biological response

Question 2

What are the phases of gastrointestinal secretions?

Answer 2

-cephalic
-gastric
-intestinal

Question 3

What triggers the cephalic secretory phase?

Answer 3

sight, smell, or thought of food

Question 4

What triggers the gastric secretory phase?

Answer 4

presence of food in stomach

Question 5

What triggers the intestinal secretory phase?

Answer 5

presence of food in intestines

Question 6

What secretions are produced during the cephalic secretory phase?

Answer 6

-majority of salivary secretion
-20-30% of gastric and pancreatic secretions

Question 7

What secretions are produced during the gastric secretory phase?

Answer 7

-60% of gastric acid secretion
-5-10% of pancreatic secretions

Question 8

What secretions are produced during the intestinal secretory phase?

Answer 8

-70% of pancreatic secretions
-10% of gastric acid secretion

Question 9

Which organs/glands receive parasympathetic vagus nerve input during the cephalic phase?

Answer 9

-salivary glands
-gastric glands
-pancreas

Question 10

Which nerves provide parasympathetic innervation to just the salivary glands?

Answer 10

-glossopharyngeal nerve
-facial nerve

Question 11

What are the functions of saliva?

Answer 11

-lubricate food
-begin digestion process
-antibacterial activity
-evaporative cooling
-pH regulation

Question 12

How does saliva play a role in pH regulation?

Answer 12

bicarbonate in saliva neutralizes acids produced by bacteria

Question 13

What type of saliva is produced by animals with simple stomachs?

Answer 13

neutral saliva

Question 14

What type of saliva is produced by ruminants?

Answer 14

basic saliva with high concentrations of phosphate ions (in large quantities)

Question 15

What are the two functional areas of the stomach?

Answer 15

-oxyntic glands
-pyloric glands

Question 16

Which cells are found within the oxyntic glands?

Answer 16

-parietal cells
-enterochromaffin-like cells
-D-cells
-chief cells

Question 17

Which cells are found within the pyloric glands?

Answer 17

-D-cells
-G-cells

Question 18

What are the stimuli for gastrin release?

Answer 18

-stretch
-peptides
-amino acids
-acetylcholine

Question 19

What are the effects of gastrin?

Answer 19

-activation of parietal cells
-activation of enterochromaffin-like cells
-promotion of epithelial growth in stomach/duodenum
-activation of pancreatic acinar cells

Question 20

What is the stimulus for histamine release?

Answer 20

gastrin

Question 21

What is the effect of histamine?

Answer 21

activation of parietal cells

Question 22

What are the characteristics of parietal cells?

Answer 22

-secrete HCl
-activated by 3 secretagogues: acetylcholine, gastrin, and histamine

Question 23

What happens once a parietal cell is activated?

Answer 23

-conformational change in which luminal membranes become enfolded; increases surface area for gastric acid secretion
-insertion of H+/K+/ATPases in the membrane, which become proton pumps

Question 24

Which type of receptor does histamine interact with on parietal cells?

Answer 24

H2

Question 25

Which secretagogue is the most potent for parietal cells?

Answer 25

histamine

Question 26

What are the characteristics of parietal cell proton pumps?

Answer 26

-secrete acid solution with 0.8 pH
-carbonic anhydrases catalyze combination of CO2 and OH- to produce bicarbonate
-bicarbonate is secreted into interstitial fluid while Cl- ions enter cell

Question 27

Which cells produce pepsinogen?

Answer 27

chief cells

Question 28

What are the stimuli for pepsinogen production?

Answer 28

-acetylcholine
-HCl

Question 29

What is pepsinogen?

Answer 29

enzyme precursor of pepsin

Question 30

When does pepsinogen get activated into pepsin?

Answer 30

in the presence of acid

Question 31

What are the characteristics of pepsin?

Answer 31

-begins protein digestion
-mostly digests collagen
-only provides 10-20% of total protein digestion

Question 32

What is the stimulus for somatostatin secretion?

Answer 32

rapid drop in gastric pH

Question 33

What are the actions of somatostatin?

Answer 33

-inhibit gastrin secretion
-inhibit parietal cell acid secretion
-inhibit gastric motility