Hormones and Gastric Secretions

Question 1

Gastrin

• What cells/organ secrete this hormone?
• What is the stimulus that causes the release of this hormone?
• What are its targets?
• What are its effects?

Answer 1

• G cells in stomach (antrum)
• Peptides, distension, Input from CNX that causes release of gastric releasing peptide (GRP) onto G cells
• Targets –> effects:
  
  • GI smooth muscle –> (+) gastric emptying and motility
  • Parietal cells –> (+) HCl and intrinsic factor
  • Enterochromaffin-like (ECL) cells –> (+) secretion of histamine which will increase HCl also

Question 2

Cholecystokinin

• What cells/organ secrete this hormone?
• What is the stimulus that causes the release of this hormone?
• What are its targets?
• What are its effects?

Answer 2

• I cells of duodenum
• Peptides and fatty acids
• Targets –> Effects:
  
  • Gallbladder –> (+) contraction to release bile into duodenum
  • GI smooth muscle –> (-) gastric motility and (+) intestinal motility
  • Pancreatic acinar cells –> (+) pancreatic enzyme secretion

Question 3

Secretin

• What cells/organ secrete this hormone?
• What is the stimulus that causes the release of this hormone?
• What are its targets?
• What are its effects?

Answer 3

• S-cells of duodenum
• Protons from gastric acid reaching duodenum or fatty acids in duodenum
• Targets –> Effects:
  
  • GI smooth muscle –> (-) gastric motility and secretion and (+) intestinal motility
  • Pancreatic duct cells –> (+) pancreatic duct secretion (water and bicarb)

Question 4

Glucose dependent insulinotropic Peptide (GIP)

• What cells/organ secrete this hormone?
• What is the stimulus that causes the release of this hormone?
• What are its targets?
• What are its effects?

Answer 4

• K-cells in duodenum and jejunum
• Carbs
• Targets –> Effects:
  
  • GI smooth muscle –> (-) gastric motility, (+) intestinal motility
  • Parietal cells –> (-) HCl secretion
  • Pancreatic beta cells –> (+) insulin secretion

Question 5

Motilin

• What cells/organ secrete this hormone?
• What is the stimulus that causes the release of this hormone?
• What are its targets?
• What are its effects?

Answer 5

• M cells in duodenum
• Fasting
• Targets –> Effects:
  
  • GI smooth muscle –> (+) gastric motility (+) small bowel motility

Question 6

What are the important neurocrine factors to know? What is a neurocrine factor?

Answer 6

VIP

GRP

Endorphins

These are synonymous with neurotransmitters (see image for example)

Question 7

VIP

• Leads to production of what compound?
• Effect on GI and vascular smooth muscle?
• Effect on secretion?

Answer 7

• NO
• Relaxation
• (+) pancreatic and intestinal secretion

Question 8

GRP

• Where is this released from?
• What does it stimulate?

Answer 8

• Released from post-ganglionic fibers of Vagus nerve
• Stimulates gastrin release from g cells

Question 9

Endorphins / Enkephalins

• When are these released
• What do they do
• How are they used clinically

Answer 9

Question 10

What are the 2 important paracrine factors to know for GI system?

Answer 10

Histamine

Somatostatin

Question 11

Histamine

• Source
• Stimulus
• Function

Answer 11

• ECL cells
• Gastrin and Ach
• (+) H+ secretion from parietal cells

Question 12

Somatostatin

• Source
• Stimulus
• Function

Answer 12

• (1) D-cells in stomach and duodenal mucosa (2) pancreas
• Protons
• Inhibit gastric motility and acid secretion

Question 13

In the region of the stomach circled in blue in the image:

• What are the major secretions?
• What are the glands called?
• Decribe the motility happening in region.

Answer 13

• Mucus and HCO3-
• Cardiac glands
• Prevention of reflux of stomach contents, entry of food

Question 14

In the region of the stomach circled in yellow in the image:

• What are the major secretions?
• What are the glands called?
• Decribe the motility happening in region.

Answer 14

Question 15

In the region of the stomach circled in green in the image:

• What are the major secretions?
• What are the glands called?
• Decribe the motility happening in region.

Answer 15

Question 16

Mucus glands:

• Location?
• Secretion?

Answer 16

• Throughout stomach
• Mucus, HCO3-

Question 17

Chief cells:

• Location?
• Secretion?

Answer 17

• Fundus and body of stomach
• Pepsinogen

Question 18

Parietal cells:

• Location?
• Secretion?

Answer 18

• Fundus and body
• HCl, intrinsic factor

Question 19

ECL cells:

• Location?
• Secretion?

Answer 19

• Near parietal cells
• Histamine

Question 20

D cells:

• Location?
• Secretion?

Answer 20

• Throughout GI tract (stomach, intestines, pancreas)
• Somatostatin

Question 21

G cells:

• Location?
• Secretion?

Answer 21

• Antrum and duodenum
• Gastrin

Question 22

Describe the composition of gastric juice.

Answer 22

Question 23

What are the major stimulatory regulators of Gastric secretion?

Answer 23

Gastrin

GRP

Histamine

Ach

Question 24

What are the major inhibitory regulators of Gastric secretion?

Answer 24

Somatostatin

GIP

Secretin

CCK

Question 25

How do parietal cells produce acid?

Answer 25

Have carbonic anhydrase in cell that makes H+ and HCO3-. HCO3- is secreted into blood, H+ is moved into vesicles which are then trafficked to apical membrane to release H+ when signaled to do so by gastrin, histamine and Ach. When bicarb is moved to blood, Cl- enters cell –> this is secreted with H+ into stomach as HCl

Question 26

When acid is present in the antrum of the stomach, […] will act to decrease gastrin release and acid secretion.

Answer 26

Somatostatin

Question 27

When acid is present in the duodenum, […] will act to decrease gastrin and acid secretion.

Answer 27

Secretin

Question 28

When fats and peptides are present in the duodenum, […] will be released to decrease acid secretion.

Answer 28

CCK

Question 29

When carbohydrates are present in the duodenum, […] will be released to decrease gastrin and acid secretion.

Answer 29

GIP

Question 30

How do the following OTC drugs lead to inhibition of gastric acid secretion:

• Zantac
• Prilosec
• Tums

Answer 30