Regulation of GI Function II Flashcards

1
Q

The active hormone gastrin is generated from a

A

Prepropeptide

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2
Q

What are the two major forms of Gastrin?

A

G-34 (10%)

G-17 (85%)

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3
Q

The terminal 4-aa sequence of Gastrin has

A

Biological activity

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4
Q

Which two receptors have over 50% sequence homology?

A

CCK-1 and CCK-2

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5
Q

Has a 1000-fold affinity for CCK

A

CCK-1

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6
Q

Has a high affinity for both CCK and Gastrin

A

CCK-2/gastrin receptor

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7
Q

Regulates gastric acid secretion both directly and indirectly

A

Gastrin

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8
Q

Gastrin DIRECTLY stimulates gastric acid secretion by acting directly on

A

Parietal cells via CCK-2 receptors

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9
Q

Acts indirectly via enterochromaffin-like (ECL) cell mediated histamine release to stimulate parietal cells

A

Gastrin

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10
Q

Gastrin acts indirectly to stimulate parietal cells via

A

Enterochromaffin-like (ECL) cell-mediated histamine release

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11
Q

Vagal activation stimulates multiple responses to regulate

A

Acid secretion

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12
Q

Stimulates gastric motility, helping to propel the food bolus distally

A

Gastrin

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13
Q

Also stimulates mucosal proliferation

A

Gastrin

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14
Q

Due to gastrin stimulation, we see an increase in ECL number resulting in

A

ECL hyperplasia

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15
Q

Gastrin stimulates mucosal proliferation and this increases the number of

A

Parietal cells

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16
Q

What three things stimulate Gastrin secretion?

A
  1. ) Meals (proteins, peptides, AAs)
  2. ) High Gastric pH
  3. ) Vagal stimulation
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17
Q

What are the two types of vagal stimulation that stimulate gastrin release?

A

Gastrin-releasing peptide and Gastric distension

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18
Q

What are the 4 factors that inhibit gastrin release?

A
  1. ) Fasting
  2. ) Low gastric pH
  3. ) SOMATOSTATIN
  4. ) CCK
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19
Q

We can see dilation of gastric glands and elongated parietal cells as the result of

A

Long-standing PPI use

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20
Q

Has molecular forms that range in size from 4-83 amino acids

A

Cholescystokinin (CCK)

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21
Q

The predominant molecular form of CCK is

A

CCK-58

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22
Q

Concentrated in the proximal small intestine (and brain)

-Responsible for CCK secretion

A

I cells

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23
Q

CCK is mostly distributed and secreted in the

A

Duodenum and Jejunum

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24
Q

Gastrin is mostly distributed and released in the

A

Pyloric antrum (and some duodenum)

25
Q

Extend neuropods that allow paracrine and neurocrine actions

A

CCK

26
Q

What are the two main biologic actions of CCK?

A
  1. ) Stimulates gallbladder contraction

2. ) Relaxes sphincter of Oddi

27
Q

Stimulates pancreatic enzyme secretion

A

CCK

28
Q

Delays gastric emptying and inhibits gastric secretion

A

CCK

29
Q

CCK inhibits the rate and force of

A

SMC contraction

30
Q

By delaying gastric emptying, CCK contributes to the feeling of

A

Satiety

31
Q

Found in the duodenum and jejunum (and brain)

A

Secretin (or S-cells)

32
Q

S-cells are classified as

A

pH sensors

33
Q

Granule contents are released from the basolateral surface of

A

S cells

34
Q

Secretin has a half life of

A

2-3 minutes

35
Q

Secretin is distributed and released in the

A

Duodenum, Jejunum, and Ileum

36
Q

Stimulates bicarbonate production

A

Secretin

37
Q

Secretin stimulates bicarbonate production by the

A

Pancreatic duct cells, cholangiocytes, and Brunner’s glands in the duodenum

38
Q

What are the three effects of secretin on the stomach

A
  1. ) Reduces acid secretion
  2. ) Slows gastric emptying
  3. ) Inhibits gastrin secretion
39
Q

Secretin increases cAMP to activate

A

PKA

40
Q

What is the main function of secretin from an ion standpoint?

A

Increases conductance of the CFTR channel leading to outflow of chloride

41
Q

What regulates secretin secretion?

A

Acid

42
Q

Acidification of the duodenal lumen causes which two things?

A
  1. ) Secretin release into the plasma

2. ) Pancreatic HCO3- secretion is increased

43
Q

Secretin levels can also be increased by

A

Fatty Acids

44
Q

There is increased bicarbonate-rich secretion by

A

Cholangiocytes

45
Q

What are the two major forms of somatostatin?

A

S-28 and S-14

46
Q

Secrete somatostatin

-closely coupled to target cells

A

D Cells

47
Q

Functions to decrease acid and pepsinogen secretion

A

Somatostatin

48
Q

Somatostatin also decreases

A

Pancreatic and small intestine secretion as well as gall bladder contraction

49
Q

The most important hormone during the interdigestive period

-sets it apart from other hormones

A

Motilin

50
Q

Motilin is released cyclically during

A

Fasting

51
Q

Motilin has a PRO-kinetic effect. I.e. it enhances

A

Bowel motility

52
Q

Enhances phase 3 contractions

A

Motilin

53
Q

Produced in the stomach and duodenum where it stimulates gastric contraction and enhances stomach emptying

A

Ghrelin

54
Q

Ghrelin stimulates appetite and promotes

A

Weight gain

55
Q

Serotonin (5-HT) is released by

A

EC cells

56
Q

Functions to initiate peristaltic and segmentation activity in the small intestine

A

Serotonin

57
Q

Seratonin functions in neural-mediated secretion of

A

Chloride and Bicarbonate

58
Q

Functions in vasodilation

A

Seratonin

59
Q

Tryptophan metabolism regulates

A

Seratonin