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603 Physiology > GI 2 > Flashcards

GI 2 Flashcards

1
Q

3 Regulatory Substances

A
  1. Neurocrines
  2. Paracrines
  3. Hormones
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2
Q

Neurocrine

A

from the neurons of the GI tract, released following an AP, and can travel up to the length of the axon and across a synapse to act on target cells

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3
Q

Hormones

A

release from endocrine cells and secreted into the blood to travel to target (long distance)

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4
Q

Paracrine

A

secreted by endocrine cells and act locally within the same tissue that secretes them (short distance)

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5
Q

Examples of Neurocrines

A

acetylcholine, norepinephrine, vasoactive intestinal peptide (VIP), gastrin releasing peptide (GRP)

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6
Q

Are neurocrines excitatory or inhibitory?

A

BOTH, can promote secretion while also inhibiting contracting, or vice versa

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7
Q

4 Criteria to be a GI Hormone

A
  1. Secretion in sponse to physiological stimuli
  2. Independent of any neural activity
  3. Can be isolated and identified
  4. Can reproduce physiologic effect following injection into bloodstream
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8
Q

“open” endocrine cells

A

endocrine cells which contact the intestinal lumen

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9
Q

When are hormones released into the GI tract (in response to what?)

A

in response to nervous activity, chmical, and mechanical signals conincidents with food digestion

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10
Q

Morphology of an Enteroendocrine cell

A

Narrow apex with a broad base, full of vesicles with hormones and paracrines

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11
Q

What is the only hormone you will find in the stomach?

A

gastrin

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12
Q

What part of the GI tract will you find the most hormones?

A

duodenum and jejunum (major site of digestion and absorption)

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13
Q

What hormones might you find in the ileum?

A

CCK and secretin, in small amounts

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14
Q

Will you find any hormones in the colon?

A

No (if you do it could be a sign of disease)

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15
Q

How do GI hormones act on the digestive tract?

A

they act distally from where they are released

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16
Q

What hormone can have a feedback reflex to the stomach to reduce movement?

A

CCK

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17
Q

crosstalk

A

hormones that bind to receptors in afferent nerves and amplify their action by simultaneous recruitment of neurocrines

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18
Q

4 Gastrointestinal Hormones

A
  1. Gastrin
  2. Cholecystokinin (CCK)
  3. Secretin family
  4. Motilin family
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19
Q

What do gastrin and CCK have in common?

A

identical C-terminal AAs, they are initially long peptides and then cleaved to active forms

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20
Q

Secretin family

A

includes secretin, gastric inhibitory peptide (GIP), and vasoactive inhibitory polypeptide (VIP), share some AA sequence

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21
Q

Where does the secretin family of hormones bind?

A

bind to G-protein recptors to increase intracellular levels of cyclic AMP (cAMP)

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22
Q

Where do gastrin and CCK bind?

A

bind to G-protein coupled receptors they both increase cytoplasmic calcium level

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23
Q

In what state are motilin hormones relased?

24
Q

Migrating motor complex

A

an interdigestive phase to clear ingesta residues

25
Q

Function of Motilin

A

to stimulate gastrointestinal motility during the interdigestive phase

26
Q

Gastrin function

A

to acidify the lumen of the stomach

27
Q

Where is gastrin synthesized?

A

G cells of the antrum mucosa
forms G17, the short form of gastrin

28
Q

Gastrin target cells

A

acid-secreting parietal cells and enterochromaffin-like cells

29
Q

Direct Effect of Gastrin

A

binds to CCK2 on parietal cells to inc. acid secretion

30
Q

Indirect Effect of Gastrin

A

binds to CCK2 on ECLs to stimulate histamine release which also inc. acid secretion from parietal cells

31
Q

cephalic phase

A

no food in stomach or small intestine

32
Q

Gastrin stimuli

A

cephalic phase, breakdown products, physical distension of the stomach

33
Q

Somatostatin

A

paracrine which inhibits gastrin, secretin, and CCK release

34
Q

Cholecystokinin (CCK) functions

A
  1. Promote pancreatic enzyme secretion
  2. Promote bile secretion
  3. Inhibit gastric emptying
  4. Generate satiety
35
Q

Where is CCK synthesized?

A

I cells of the duodenum and jejunum

36
Q

What stimulates the release of CCK?

A

digestion of FAT (and protein)

37
Q

4 Organs that are the Target of CCK

A
  1. Brain
  2. Gallbladder
  3. Pancreas
  4. Stomach
38
Q

CCK effect on gallbladder

A

release of bile (relaxation of sphincter of Oddi and contraction of the gallbladder)

39
Q

CCK effect on brain

A

tells you not to eat more (satiety - fullness)

40
Q

CCK effect on stomach

A

inhibits gastric emptying to provide time for digestion and absorption

41
Q

CCK effect on pancreas

A

targets to acinar cells to secrete pancreatic enzymes, and secondarily bicarbonate secretion

42
Q

What is the master regulator of the duodenal cluster unit?

43
Q

Secretin function

A

neutralize acid in the lumen of the small intestine

44
Q

Where is secretin synthesized?

A

S cells of the duodenum

45
Q

Main stimulation of secretin release?

A

Duodenal pH of less than 4.5
(also fatty acids)

46
Q

What is substance P an inhibtor of?

47
Q

“Nature’s Antacid”

48
Q

Targets of Secretin

A
  1. Stimulate Duoednum, Pancreas, and Liver to secrete bicarbonates
  2. Inhibit gastrin release in the Stomach
49
Q

Two Paracrines

A
  1. Somatostatin
  2. Histamine
50
Q

Is somatostatin inhibitory or excitatory?

A

Inhibitory

51
Q

Where is somatostatin synthesized?

A

D cells in the gastric and duodenal mucosa

52
Q

Is histamine a peptide?

53
Q

What does somatostatin inhibit in the stomach?

A

inhibits release of gastrin, histamine, and acid from parietal cells

54
Q

What does somatostatin inhibit in the intestine, pancreas, and liver?

A

inhibits release of GI hormones (secretin, CCK)

55
Q

Histamine Target Cells

A

ECLs and mucosal mast cells

56
Q

Main Function of Histamine in the GI

A

stimulate acid secretion

603 Physiology (22 decks)

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