GI Regulatory Substances

Question 1

What are the four GI functions?

Answer 1

• contraction/relaxation of smooth muscle and sphincters
• secretion of enzymes, fluid, and electrolytes
• trophic effects on tissues
• secretion of other GI peptides

Question 2

What substances regulate GI functions?

Answer 2

• GI peptides (short amino acid sequences) including hormones (proteins), neurocrines, and paracrines

Question 3

What are the four GI hormones?

Answer 3

• gastrin
• cholecystokinin (CCK)
• secretin
• glucose dependent insulinotropic peptide (AKA gastric inhibitory peptide (GIP))

Question 4

GI peptides can be hormones, paracrines, or neurocrines depending on what?

Answer 4

where subtance is released and the route taken to reach the target cell

Question 5

What type of GI peptide is released from endocrine cells of GIT (not glands) then enters the portal circulation, liver, systemic circulation, or target cells?

Answer 5

Hormones

Question 6

What type of GI peptide is secreted by endocrine cells of GIT and acts locally within the same tissue that secretes them?

Answer 6

paracrines

Question 7

What is the major GI paracrine hormone?

Answer 7

somatostatin (major inhibitory actions)

Question 8

What type of GI peptide is synthesized in neurons of GIT and released after an action potential?l

Answer 8

neurocrines

Question 9

What are the major neurocrines?

Answer 9

• acetylcholine
• norepinephrine
• vasoactive intestinal polypeptide (VIP)
• gastrin releasing peptide (GRP)
• enkephalins
• neuropeptide Y
• substance P

Question 10

What GI hormone functions to promote hydrogen ion secretion by gastric parietal cells, stimulate growth of gastric mucosa, and increase gastric motility?

Answer 10

gastrin

Question 11

What are the two forms of gastrin?

Answer 11

• big gastrin
• little gastrin

Question 12

Which form of gastrin is secreted between meals at low basal levels?

Answer 12

big gastrin

Question 13

Which form of gastrin is secreted in response to a meal (distension of stomach, presence of amino acids and peptides)?

Answer 13

little gastrin

Question 14

What is the local vagal reflex of gastrin?

Answer 14

Gastrin releasing peptide (GRP) released from vagal nerves onto G cells

Question 15

How is gastrin secretion inhibited?

Answer 15

• low gastric pH
• somatostatin

Question 16

Gastrin is secreted by what cells in stomach?

Answer 16

G cells

Question 17

What GI hormone is secreted in response to presence of fatty acids, amino acids, and peptides?

Answer 17

Cholecystokinin (CKK)

Question 18

Cholecystokinin (CKK) is secreted by what type of cells in the duodenal and jejunal mucosa?

Answer 18

I cells

Question 19

What are the five actions of cholecystokinin (CKK)?

Answer 19

• contraction of gallbladder
• secretion of pancreatic enzymes (lipase, amylase, protease)
• secretion of bicarbonate from pancrease
• growth of exocrine pancreas and gallbladder
• inhibition of gastric emptying

Question 20

What is the function of the exocrine pancreas?

Answer 20

makes enzymes and bicarbonate

Question 21

What is the function of the endocrine pancreas?

Answer 21

produce insulin and hormones

Question 22

When cholecystokinin increases gastric emptying time, it allows for what?

Answer 22

adequate time for digestion and absorption

Question 23

What GI hormone is secreted in response to H ions and fatty acids present in small intestine?

Answer 23

Secretin

Question 24

Secretin is secreted by what type of cells in the duodenum?

Answer 24

S cells

Question 25

What is the function of secretin?

Answer 25

- stimulates secretion of pancreatic and biliary bicarbonate - inhibits gastrin release from G cells in stomach

Question 26

What GI hormone is secreted in response to glucose, amino acids, and fatty acids?

Answer 26

Gastric inhibitory peptide (GIP)

Question 27

Gastric inhibitory peptide is secreted by what cells of duodenum and jejunum?

Answer 27

K cells

Question 28

Does intravenous glucose stimulate gastric inhibitory peptide?

Answer 28

No, only oral glucose load

Question 29

What are the functions of gastric inhibitory peptide (GIP)?

Answer 29

- stimulates insulin secretion - inhibits gatric H ion secretion and gastric emptying

Question 30

What type of hormones are not cisdered true GI hormone due to not meeting one or more criteria?

Answer 30

candidate hormones

Question 31

What are the four candidate hormones?

Answer 31

- motilin - pancreatic polypeptide - enteroglucagon - glucagon like peptide 1 (GLP 1)

Question 32

Which candidate hormone is secreted by the upper duodenum during fasting?

Answer 32

motilin

Question 33

What candidate hormone is secreted by pancreas in response to ingestion of carbs, proteins, and lipids?

Answer 33

Pancretic polypeptide

Question 34

Which candidate hormone is secreted by intestinal cells in response to decreased blood glucose?

Answer 34

enteroglucagon

Question 35

Which candidate hormone is secreted by L cells of small intestine in response to nutrients?

Answer 35

glucagon like peptide 1 (GLP 1)

Question 36

What is the function of motilin?

Answer 36

increase GI motility by initiating "interdigestive myoelectric complexes" at 90 minute intervals to move indigestible substances and bacteria to colon

Question 37

What is the function of pancreatic polypeptide?

Answer 37

self regulates pancreatic secretion by inhibiting pancreatic secretion of bicarbonate and enzymes

Question 38

What is the function of enteroglucagon?

Answer 38

stimulates liver to increase glycogenolysis and increase gluconeogenesis

Question 39

What is the function of GLP 1?

Answer 39

stimulates insulin secretion from panreatic beta cells to inhibit glucagon secretion, decrease gastric emptying, and inhibit appetite

Question 40

What are the GI paracrines?

Answer 40

- somatostatin - histamine

Question 41

Which GI paracrine is secreted by D cells of GI mucosa in response to decreased luminal pH?

Answer 41

Somatostatin

Question 42

What is the function of somatostatin?

Answer 42

inhibits secretion of other GI hormones and gastric H ion secretion

Question 43

Which GI paracrine has major secretion from H ion secreting area of stomach?

Answer 43

histamine

Question 44

What is the function of histamine?

Answer 44

stimulates H ion secretion by gastric parietal cells

Question 45

Where is the statiety center?

Answer 45

located in ventromedial nucleus of hypothalamus

Question 46

Where is the feeding center?

Answer 46

located in lateral hypothalamic area

Question 47

What occurs is satiety center?

Answer 47

anorexigenic neurons release pro-opiomelanocortin to decrease appetite

Question 48

What occurs in feeding center?

Answer 48

orexigenic neurons release neuropeptide Y to increase appetite

Question 49

What substances can influence (stimulates) anorexigenic neurons to derease appetite?

Answer 49

- leptin - insulin - GLP-1 - Peptide YY

Question 50

What substances can influence (stimulates) orexigenic neurons to increase appetite?

Answer 50

ghrelin

Question 51

What cells secrete ghrelin?

Answer 51

gastric cells

Question 52

Peptide YY is secreted by what type of cells/

Answer 52

intestinal L cells

Question 53

Peptide YY has a direct affect on what?

Answer 53

hypothalamus

Question 54

What inhibits ghrelin?

Answer 54

Peptide YY

Question 55

GLP is synthesized and secreted by what cells?

Answer 55

intestinal L cells

Question 56

Leptin is secreted by what cells?

Answer 56

fat cells