Lecture 6 - GI Hormones

Question 1

How many forms of gastrin are there and what are they?

Answer 1

1. ) Big - 34 amino acids
2. ) little - 17 amino acids
3. ) mini - 14 amino acids

all of these active forms have the same c terminal 5 chain AA

Question 2

How are gastrin released?

Answer 2

released by the stomach and duodenum from G cells. It is also present in the CNS in the pituitary and hypothalamus

Question 3

What is the stimuli for gastrin?

Answer 3

Protein digestion products
nervous physical distention
calcium, coffee, wine

Question 4

What inhibits gastrin?

Answer 4

Acidification of antrum - decreased pH and also somatostatin

Question 5

What is the action of gastrin?

Answer 5

1. ) stimulates acid secretion by gastric mucosa
2. ) Stimulates growth of parietal cells of the gastric mucosa
3. ) Stimulates mucosal blood flow
4. ) stimulates pepsin release

Question 6

What is gastrinoma or also known as zollinger ellison syndrome?

Answer 6

Gastrin secreting tumor, non beta cell tumor of pancreas (80%) or G cell tumor in duodenum (20%). It continually secretes gastrin into the blood.

Question 7

Symptoms of gastrinoma?

Answer 7

duodenal ulcers, diarrgea, steatorrhea, hypokalemia. Increased parietal cell mass and constant stimulation of hyperplastic mucosa.

Question 8

What is cholecystokinin?

Answer 8

polypeptide with many forms like 58,39, 33, and 8 AA. The 8 amino acid form has full biological potency.

Question 9

What secreted CCK?

Answer 9

I cells in duodenum and jejenum

Question 10

What stimulates CCK secretion?

Answer 10

Fatty acids or AA in the duodenum, negative feedback between the CCK secretion and its stimulus.

Question 11

What inhibits CCK secretion?

Answer 11

Somatostatin

Question 12

What are the physiological effects of CCK?

Answer 12

1. ) emptying of gallbladder by contracting the gallbladder and relaxation of sphincter.
2. ) pancratic exocrine function - potent stimulator of enzyme secretion
3. ) inhibits gastric emptying
4. ) Trophic effect - exocrine pancreas and gallbladder mucosa
5. ) induces satiety

Question 13

What is secretin?

Answer 13

29 AA released from S cells in the duodenum

Question 14

What stimulates the release of secretin?

Answer 14

Acid in duodenum - when its less than 4.5

Fatty acids in the duodenum

Question 15

Physiological effects of secretin (nature’s antiacid)

Answer 15

1. ) Inhibits gastric acid secretion
2. ) Stimulates pancreatic and bile bicarbonate secretion
3. ) Stimulates pepsin secretion
4. ) Trophic effect on exocrine pancreas
5. ) May have a role in food intake

Question 16

What is gastric inhibitory peptide (GIP)?

Answer 16

9 AA identical to secretin

Question 17

Stimuli for GIP?

Answer 17

Released from duodenum and proximal jejenum. All major foodstuffs

Question 18

Physiological effects of GIP?

Answer 18

Stimulates insulin release and inhibits gastric acid secretion.

Question 19

What is motilin?

Answer 19

22 AA peptide

Question 20

What is the stimuli for motilin?

Answer 20

Released from the duodenum and proximal jejenum during fasting at 100 min intervals. Release under neural control.

Question 21

What is the physiological effects of motilin?

Answer 21

Stimulates the upper GI motility and accounts for the migrating motility complex.

Question 22

What is somatostatin?

Answer 22

14 amino acids or 28

Question 23

Where is somatostatin found?

Answer 23

In the hypothalamus throughout the CNS and gut (including the pancreas)

Question 24

What does somatostatin inhibit?

Answer 24

Major inhibitory peptide of the gut:

1. ) insulin
2. ) glucagon
3. ) CCK
4. ) secretin
5. ) gastrin
6. ) VIP
7. ) somatostatin (autocrine)