Ward, Gastric Phys Part 2 (continued from Week 1)

Question 1

What are the three ways that gastric secretion is regulated?

Answer 1

neural, hormonal, and paracrinal factors

Question 2

How is gastric secretion regulated neurally?

Answer 2

vagal nerve stimulation

Question 3

How is gastric secretion regulated hormonally?

Answer 3

via histamine and gastrin :)

Question 4

What does ACh do for gastric secretion?

Answer 4

it stimulates the secretion of substances such as pepsinogen, HCL, mucus and gastrin

Question 5

What does Gastrin and Histamine do?

Answer 5

Stimulate release of HCl by parietal cells.

Question 6

What receptors does histamine work on? Knowing what histamine does and what receptors it works on, how would we reduce acid secretion?

Answer 6

H2 receptors
use cimentidine (an antagonist of H2 receptors)

Question 7

Where do we get histmaine?

Answer 7

via mast cells in LP

Question 8

What is this:
Occurs before the food bolus enters the stomach. Initiated by smell, sight, taste etc. The greater the appetite the more intense the stimulation.

Answer 8

cephalic phase

Question 9

Describe the innervation of the cephalic phase i.e how we get to be mouth watering

Answer 9

Cerebral cortex/ amygdala/ hypothalamus-»vagus to the stomach-> stimuate GRP (gastrin releasing peptide)–> G cells release gastrin–> stimulate parietal cells.

Question 10

What percentage of gastric secretion is associated with cephalic phase?

Answer 10

20-30%

Question 11

What is this:
Gastric distension and partially digested proteins stimulate mechano-receptors which stimulate paretial cells through short local enteric reflexes and long vagovagal reflexes.

Answer 11

Gastric Phase

Question 12

Explain the innervation of the gastric phase?

Answer 12

gastric distention and partially digested proteins

• ->local enteric reflexes, long vagovagal reflexes
• -> gastric secretion

Question 13

What percentage of gastric secretion is associated with gastric phase?

Answer 13

60%

Question 14

When we think about stimulating parietal cells what 2 things should we be thinking about?

Answer 14

Ach

gastrin

Question 15

What is this:
The presence of proteins in the duodenum can cause the release of small amounts of gastric juices possibly through release of gastrin. Distension of the intestine also causes acid secretion possibly through the release of enterooxyntin, a hormone from endocrine cells.

Answer 15

Intestinal Phase

Question 16

Explain the intestinal phase

Answer 16

Distension of intestion->release of enterooxyntin–>acid secretion

Question 17

What percentage of gastric secretion is associated with the intestinal phase?

Answer 17

10%

Question 18

Main Instigator of Gastric secretion:
Cephalic?
Gastric?
Intestinal?

Answer 18

Cephalic-> vagus
Gastric-> local reflex, vagal reflex, gastrin
Intestinal-> nervous and hormonal

Question 19

The vagal efferents tend to innervated the gut at the (blank) however the vagus affarents lie in the (blank).

Answer 19

nerve plexus
enteric plexus (or plexus independent)

Question 20

What is the main target of all three phases of gastric secretion?

Answer 20

stimulating those G cells to secrete gastrin :)

Question 21

How can we decrease secretion of acid?

Answer 21

Enterogastric reflexes:
distention, acid in intestine, protein breakdown products and irritation of mucosa will inhibit secretion via ENS and vagal nerves

Question 22

It seem like what stimulates acid is what inhibits it?

Answer 22

there is a balance, so if we are too acidic, enteric and vagal will sense this etc.

Question 23

What will acid, fat protein breakdown products, hyper-hypo osmotic fluids make the intestines release?

Answer 23

secretin, somatostatin and CCK

Question 24

(blank) is important for inhibiting gastric emptying as well as playing a significant role in the emptying of bile from the gallbladder

Answer 24

CCK

Question 25

VIP and gastric inhibitory peptide (GIP) inhibit what?

Answer 25

secretion and gastric motility

Question 26

When the stomach gets too acidic (below 3) how do we get G cells to stop making gastrin so that Parietal cells to stop producing gastric acid (HCl)?

Answer 26

endocrine cells (D cells) in the antrum release somatostatin the inhibits gastring and gastric secretion

Question 27

Where do we find the most parietal cells?

Answer 27

the fundus

Question 28

What all stimulate parietal cells to secrete acid?

Answer 28

gastrin Ach histamine

Question 29

How do we inhibit gastrin release and inhibition acid secretion in the antrum?

Answer 29

somatostatin

Question 30

What does the nervous reflex of the duodenum inhibit?

Answer 30

acid secretion

Question 31

When you have a hyperosmotic solution in the duodenum what happens?

Answer 31

it stimulates the inhibition of acid secretion

Question 32

(blank) is a proteolytic enzyme that is active at low pH

Answer 32

pepsin

Question 33

(blanK) secreted from mucous and chief cells can be activated by acidic environments (i.e HCl)

Answer 33

pepsinogen

Question 34

THe binding of secretagoues (a substance that produces secretion) to oxyntic cells (secretory cells) is coupled to at least 2 intracellular messengers which are (blank) and (blank)

Answer 34

intracellular calcium | cAMP

Question 35

How does ACh influence calcium?

Answer 35

it causes influx of Calcium into the oxyntic cell, resulting in acid secretion.

Question 36

The weak stimulatory effect on gastrin is also (blank) dependent

Answer 36

calcium

Question 37

Does histamine need extracellular calcium for acid secretion? WHat does it need?

Answer 37

no | cAMP

Question 38

(blank) and (Blank) cause the release of gastrin from pyloric galnds.

Answer 38

vagal and local stimulation

Question 39

What are the 2 forms gastrin comes in?

Answer 39

G34 and G17

Question 40

(blank) is absorbed and carried in the blood stream and stimulates the release of histamine from ECL cells and HCL from parietal cells

Answer 40

gastrin

Question 41

What allows for B12 to be released from dietary protein?

Answer 41

gastric acid and pepsin

Question 42

What is IF?

Answer 42

Intrinsic factor that i secreted by parietal cells

Question 43

What is essential for the absorption of vit B12 in the ileum?

Answer 43

Intrinsic Factor

Question 44

So explain the mechanism for B12 absorption

Answer 44

B12 gets released from protein by gastric acid and pepsin--> B12 binds to R protein in acidic environment-> in upper intestine B12 binds to IF-> B12 and IF bind to ileal receptor and get absobred-> B12 transported to tissues by transcobalamin II :)

Question 45

So what will B12 bind to in acidic environments?

Answer 45

R protein

Question 46

What will B12 bind to in less acidic environments?

Answer 46

IF

Question 47

What will happen to B12 when it binds with IF?

Answer 47

it gets absorbed in ileum :)

Question 48

Once B12 is absorbed how does it get to the tissues?

Answer 48

via transcobalamin II

Question 49

Where do we find IF and R protein?

Answer 49

Saliva :)

Question 50

What happens if we dont have IF?

Answer 50

we get pernicious anemia (vit B12 is needed for maturation of RBCs)

Question 51

What kind of protein is IF?

Answer 51

a glycoprotein

Question 52

What kind of cells do we find in the gastric gland?

Answer 52

``` mucous neck cells parietal cells enterchromaffin like cells Chief cells D cells G cells ```

Question 53

What do mucous neck cells secrete?

Answer 53

mucus and bicarb

Question 54

What do parietal cells secrete?

Answer 54

``` gastric acid (HCl) Intrinsic factor ```

Question 55

What do enterochromaffin-like cells secrete?

Answer 55

histamine

Question 56

What do chief cells secrete?

Answer 56

pepsin(ogen) and gastric lipase

Question 57

What do D cells secrete?

Answer 57

somatostatin

Question 58

What do G cells secrete?

Answer 58

gastrin

Question 59

What stimulated mucus release from mucous neck cells?

Answer 59

tonic secretion; increased with irritation of mucosa

Question 60

What stimulates bicarb release from mucous neck cells?

Answer 60

secreted with mucous

Question 61

What stimulates gastric acid (HCl) and IF release from parietal cells?

Answer 61

ACh, gastrin, histamie

Question 62

What stimulates pepsin(ogen) and gastric lipase from chief cells?

Answer 62

ACh, acid, secretin

Question 63

What stimulates somatostatin release from D cells?

Answer 63

acid in stomach

Question 64

What stimulates gastrin release from G cells?

Answer 64

ACh, peptides, AAs

Question 65

What is the physical barrier between lumen and epithelium?

Answer 65

mucus

Question 66

What bufferes gastric acid to prevent damage to epithelium?

Answer 66

bicarbonate

Question 67

What activates pepsin and kills bacteria?

Answer 67

gastric acid (HCl)

Question 68

What complexes with vitamin B12 to permit absorption?

Answer 68

Intrinisic Factor (IF)

Question 69

What stimulates gastric acid secretion?

Answer 69

histamine and gastrin

Question 70

What digests proteins?

Answer 70

pepsin(ogen)

Question 71

What digests fats?

Answer 71

gastric lipase

Question 72

What inhibits gastric acid secretion?

Answer 72

somatostatin

Question 73

(blank) allow for timed release of gastric contents into the duodenum?

Answer 73

pyloric openings