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Block 3 Week 3 Dani > Ward, Gastric Phys Part 2 (continued from Week 1) > Flashcards

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

1
Q

What are the three ways that gastric secretion is regulated?

A

neural, hormonal, and paracrinal factors

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2
Q

How is gastric secretion regulated neurally?

A

vagal nerve stimulation

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3
Q

How is gastric secretion regulated hormonally?

A

via histamine and gastrin :)

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4
Q

What does ACh do for gastric secretion?

A

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

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5
Q

What does Gastrin and Histamine do?

A

Stimulate release of HCl by parietal cells.

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6
Q

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

A 
H2 receptors
use cimentidine (an antagonist of H2 receptors)
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7
Q

Where do we get histmaine?

A

via mast cells in LP

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8
Q

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.

A

cephalic phase

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9
Q

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

A

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

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10
Q

What percentage of gastric secretion is associated with cephalic phase?

A

20-30%

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11
Q

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.

A

Gastric Phase

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12
Q

Explain the innervation of the gastric phase?

A

gastric distention and partially digested proteins

  • ->local enteric reflexes, long vagovagal reflexes
  • -> gastric secretion
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13
Q

What percentage of gastric secretion is associated with gastric phase?

A

60%

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14
Q

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

A

Ach

gastrin

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15
Q

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.

A

Intestinal Phase

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16
Q

Explain the intestinal phase

A

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

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17
Q

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

A

10%

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18
Q

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

A

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

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19
Q

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

A 
nerve plexus
enteric plexus (or plexus independent)
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20
Q

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

A

stimulating those G cells to secrete gastrin :)

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21
Q

How can we decrease secretion of acid?

A

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

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22
Q

It seem like what stimulates acid is what inhibits it?

A

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

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23
Q

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

A

secretin, somatostatin and CCK

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24
Q

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

A

CCK

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25
Q

VIP and gastric inhibitory peptide (GIP) inhibit what?

A

secretion and gastric motility

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26
Q

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)?

A

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

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27
Q

Where do we find the most parietal cells?

A

the fundus

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28
Q

What all stimulate parietal cells to secrete acid?

A

gastrin
Ach
histamine

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29
Q

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

A

somatostatin

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30
Q

What does the nervous reflex of the duodenum inhibit?

A

acid secretion

31
Q

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

A

it stimulates the inhibition of acid secretion

32
Q

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

A

pepsin

33
Q

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

A

pepsinogen

34
Q

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)

A

intracellular calcium

cAMP

35
Q

How does ACh influence calcium?

A

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

36
Q

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

A

calcium

37
Q

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

A

no

cAMP

38
Q

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

A

vagal and local stimulation

39
Q

What are the 2 forms gastrin comes in?

A

G34 and G17

40
Q

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

A

gastrin

41
Q

What allows for B12 to be released from dietary protein?

A

gastric acid and pepsin

42
Q

What is IF?

A

Intrinsic factor that i secreted by parietal cells

43
Q

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

A

Intrinsic Factor

44
Q

So explain the mechanism for B12 absorption

A

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 :)

45
Q

So what will B12 bind to in acidic environments?

A

R protein

46
Q

What will B12 bind to in less acidic environments?

A

IF

47
Q

What will happen to B12 when it binds with IF?

A

it gets absorbed in ileum :)

48
Q

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

A

via transcobalamin II

49
Q

Where do we find IF and R protein?

A

Saliva :)

50
Q

What happens if we dont have IF?

A

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

51
Q

What kind of protein is IF?

A

a glycoprotein

52
Q

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

A 
mucous neck cells
parietal cells
enterchromaffin like cells
Chief cells
D cells
G cells
53
Q

What do mucous neck cells secrete?

A

mucus and bicarb

54
Q

What do parietal cells secrete?

A 
gastric acid (HCl)
Intrinsic factor
55
Q

What do enterochromaffin-like cells secrete?

A

histamine

56
Q

What do chief cells secrete?

A

pepsin(ogen) and gastric lipase

57
Q

What do D cells secrete?

A

somatostatin

58
Q

What do G cells secrete?

A

gastrin

59
Q

What stimulated mucus release from mucous neck cells?

A

tonic secretion; increased with irritation of mucosa

60
Q

What stimulates bicarb release from mucous neck cells?

A

secreted with mucous

61
Q

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

A

ACh, gastrin, histamie

62
Q

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

A

ACh, acid, secretin

63
Q

What stimulates somatostatin release from D cells?

A

acid in stomach

64
Q

What stimulates gastrin release from G cells?

A

ACh, peptides, AAs

65
Q

What is the physical barrier between lumen and epithelium?

A

mucus

66
Q

What bufferes gastric acid to prevent damage to epithelium?

A

bicarbonate

67
Q

What activates pepsin and kills bacteria?

A

gastric acid (HCl)

68
Q

What complexes with vitamin B12 to permit absorption?

A

Intrinisic Factor (IF)

69
Q

What stimulates gastric acid secretion?

A

histamine and gastrin

70
Q

What digests proteins?

A

pepsin(ogen)

71
Q

What digests fats?

A

gastric lipase

72
Q

What inhibits gastric acid secretion?

A

somatostatin

73
Q

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

A

pyloric openings

Block 3 Week 3 Dani (10 decks)

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