GIT —> Gastric Secretion

Question 1

What are the 3 important phases of gastric secretion?

Answer 1

1- Cephalic (accounts for 1/3 of the gastric juice, that is secreted by the stomach)
2- Gastric (accounts for 2/3)
3- Intestinal

Question 2

Which phase is main one for gastric acid secretion?

Answer 2

• Gastric phase

Question 3

What can stimulate the cephalic phase ?

Answer 3

1- sight of food
2- thought of food
3- smell of food
4-taste of food

Question 4

When the gastric juice producing within the cephalic phase ?

Answer 4

All this gastric juice that were producing within the cephalic phase occurs before food even enters into the stomach.

Question 5

What are the main cells in GI ?

Answer 5

• Partiel cells
• Chief cells

Question 6

What chemical produced by parietal cells and chief cells?

Answer 6

• Hydrochloric acid (HCL)
• Pepsinogen (pepsin)

Question 7

What are the main contents of the gastric juice ?

Answer 7

• Pepsin
• Hydrochloric acid

Question 8

What can inhibit the cephalic phase ?

Answer 8

Anything that activate the sympathetic nervous system, it could be :
- Stress
- Emotional upset

Question 9

What can stimulate the gastric phase ?

Answer 9

• Distension (stretch)
• Partially digested proteins

Question 10

The stretch receptors found in the stomach are coupled with what nerve?

Answer 10

• Cranial nerve 10 (vagus)

Question 11

What are the special cells in the antrum of the stomach?

Answer 11

• Entero endocrine G cells

Question 12

What chemical does G cells secrete?

Answer 12

• Gastrin (a hormone)

Question 13

Gastrin binds on receptors in which cells?

Answer 13

• Parietal cells
• Chief cells

Question 14

In parietal cells Gastrin hormone will act on what receptor?

Answer 14

• Cholecystokinin (CCK-2)

Question 15

In parietal cells What will Cholecystokinin (CCK-2) do inside the cell?

Answer 15

• Increase intracellular calcium

Question 16

In parietal cells What will intracellular calcium stimulate?

Answer 16

• Proton pump (H+ out, K+ in)
  Hydrochloric acid

Question 17

In chief cells, Gastrin hormone will act on what receptor?

Answer 17

• Cholecystokinin (CCK-1)

Question 18

In chief cells What will Cholecystokinin (CCK-1) do inside the cell?

Answer 18

• Increase calcium levels, which stimulate the vesicles to fuse with the cell membrane

Question 19

In chief cells, what will happen if the vesicles fuses with the cell membrane?

Answer 19

• Formation of exocytosis (like a pocket)

Question 20

The formation of exocytosis in chief cells, what does it contain?

Answer 20

• Pepsinogen molecules

Question 21

How is pepsinogen (inactive) is converted to pepsin (active) ?

Answer 21

• A lot of protons (hydrochloric acid) will stimulate the conversion of pepsinogen into pepsin

Question 22

Gastrin hormone acting on Parietal cells receptor, i will result in?

Answer 22

• Hydrochloric acid (protons H+)

Question 23

Gastrin hormone acting on Chief cells receptor, i will result in?

Answer 23

• Pepsinogen

Question 24

What is the PH range for pepsin?

Answer 24

• 1.8 - 3.5

Question 25

What can inhibit the gastric phase ?

Answer 25

1- Anything that activate the sympathetic nervous system, it could be :
- Stress
- Depression
- Anxiety
2- Somatostatin :
It’s stimulus is really low PH (High H+)

Question 26

What is somatostatin?

Answer 26

• it’s a hormone produced in many locations, including:
• GIT
• Pancreas
• NCS
• Hypothalamus

Question 27

What does somatostatin do ?

Answer 27

• It inhibits gastric secretion

Question 28

What are the major endocrine cells in the stomach?

Answer 28

• Gastrin G cells
• Somatostatin D cells

Question 29

What is the function of G cells found in the stomach?

Answer 29

• Presence of gastric secretion

Question 30

What is the function of D cells found in the stomach?

Answer 30

• Modulate (tone down) gastric release and gastric acid secretion