Gastrointestinal Regulatory Substances Flashcards

1
Q

What substances regulate GI functions?

A

GI peptides:
hormones
neurocrines
paracrines

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2
Q

What are the release sites of GI peptides?

A

from endocrine cell or neurons (neurocrine)

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3
Q

What are the routes taken of GI peptides?

A

travel through blood
OR
act within same tissue

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4
Q

T/F: GI peptides are released from endocrine cells of GIT, not glands.

A

TRUE

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5
Q

Where do hormones enter?

A

portal circulation, liver, systemic circulation, target cells

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6
Q

What’s the target(s) of GI hormones?

A

in GIT or elsewhere

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7
Q

List the 4 GI hormones

A

gastrin
cholecystokinin (CCK)
secretin
glucose-dependent insulinotropic peptide

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8
Q

Glucose-dependent insulinotropic peptide is also called…

A

gastric inhibitory peptide (GIP)

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9
Q

Define GI paracrines.

A

secreted by endocrine cells of GIT
act LOCALLY within SAME tissue

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10
Q

What is the major GI paracrine hormone? What actions does it have?

A

somatostatin
major inhibitory actions

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11
Q

Define GI neurocrines.

A

synthesized in neurons of GIT and released after an AP

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11
Q

What are some major neurocrines.

A

acetylcholine
norepinephrine
gastrin-releasing peptide (GRP)
enkephalins
neuropeptide Y
substance P

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11
Q

Fill in the blanks

A
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11
Q

Fill in the blanks

A
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12
Q

Fill in the blanks

A
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13
Q

What is the function of gastrin?

A

promote hydrogen ion secretion (stomach releases HCl)
stimulate growth of gastric mucosa
increase gastric motility

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14
Q

Gastrin is secreted by ______ in the ______

A

G cells, stomach

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15
Q

What are the two forms of gastrin?

A

big and little

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16
Q

When is big gastrin secreted?

A

between meals and low basal levels

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17
Q

When is little gastrin secreted?

A

in response to a meal —> distention of stomach in presence of AMINO ACIDS and PEPTIDES

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18
Q

Gastrin is a local vagal reflex, where ____ is released from vagal nerves onto G cells.

A

GRP (gastrin-releasing peptide)

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19
Q

What inhibits gastrin secretion?

A

low gastric pH
somatostatin (paracrine)

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20
Q

What is Zollinger-Ellison syndrome?

A

overgrowth of gastrin mucosa
gastronoma (gastrin-secreting tumor)
INCREASES H+ ions
non-beta cell pancreas

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21
Q

What secretes cholecystokinin (CCK)? Where?

A

I cells of duodenal & jejunal mucosa

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22
Q

CCK is secreted in response to…

A

presence of fatty acids
amino acids
peptides

23
Q

What are the 5 actions of CCK?

A

contraction of gallbladder (emulsify bile)
secretion of pancreatic enzymes (lipases to release FA amylase for starch, proteases for protein)
secretion of HCO3- from pancreas
growth of exocrine pancreas & gallbladder
inhibition of gastric emptying (increases digestion)

24
Q

Fill in the blanks of CCK actions.

A
25
Q

What is secretin secreted by?

A

S cells of duodenum

26
Q

What is secretin secreted in response to?

A

H ions
fatty acids present in small intestine

27
Q

What does secretin inhibit?

A

gastrin release from G cells in stomach

28
Q

Fill in the blanks of secretin actions.

A
29
Q

What is gastric-inhibitory peptide (GIP) secreted by?

A

K cells of duodenum and jejunum

30
Q

What is GIP secreted in response to?

A

glucose, amino acids, and fatty acids

31
Q

What does GIP stimulate?

A

insulin secretion

32
Q

What stimulates GIP?

A

ORAL glucose load
NOT intravenous

33
Q

What does GIP inhibit?

A

gastric H ion secretion
gastric emptying and motility

34
Q

List the candidate hormones.

A

motilin
pancreatic polypeptide
enteroglucagon
glucagon-like peptide-1 (GLP-1)

35
Q

What are candidate hormones?

A

not considered true GI hormones because they fail to meet one or more criteria
- secreted by GIT

36
Q

What is motilin secreted by?

A

upper duodenum during FASTING

37
Q

What does motilin stimulate?

A

GI motility
interdigestive myoelectric complexes at 90 minute intervals
- trigger peristaltic waves

38
Q

What is pancreatic polypeptide secreted by?

A

pancreas in response to ingestion of carbs, proteins, and lipids

39
Q

What does pancreatic polypeptide do?

A

self-regulates pancreatic secretion
inhibits pancreatic secretion of HCO3- and enzymes

40
Q

What is enteroglucagon secreted by?

A

intestinal cells in response to decreased blood glucose

41
Q

What does enteroglucagon stimulate?

A

stimulate liver to increase glyconolysis and gluconeogenesis

42
Q

What does glucagon-like peptide-1 (GLP-1) stimulate?

A

insulin secretion from pancreatic beta cells

43
Q

Glucagon-like peptide-1 (GLP-1) is secreted by?

A

L cells of small intestine

44
Q

What is secreted in response to nutrient indigestion?

A

glucagon-like peptide-1 (GLP-1)

45
Q

What does glucagon-like peptide-1 inhibit?

A

inhibits glucagon secretion
inhibits gastric emptying
inhibits appetite

46
Q

What is somatostatin secreted by? In response to what?

A

D cells of GI mucosa
in response to decreased luminal pH

47
Q

What does somatostatin inhibit?

A

secretion of other GI hormones
gastric H ion secretion

48
Q

Where is major secretion of histamine?

A

H-ion secretion area of stomach

49
Q

What does histamine stimulate?

A

H ion secretion by gastric parietal cells

50
Q

Histamine is a _________.

A

paracrine

51
Q

Where are neurocrines synthesized?

A

cell bodies of GI neurons

52
Q

An ________ causes a release of a neurocrine.

A

action potential

52
Q

Where is a release point for neuromodulators? (peptidergic)

A

postganglionic non-cholinergic parasympathetic neurons
- VIP
- substance P
- GRP
- enkephalins
- neuropeptide Y

53
Q

Where is the satiety center located?

A

ventromedial nucleus (VPN) of hypothalamus
- something to do with arcuate nucleus

54
Q

What does the satiety center do?

A

inhibit appetite even in presence of food

55
Q

_________ neurons release pro-opiomelanocortin (POMC)

A

anorexigenic
- satiety center

56
Q

Where is the feeding center located?

A

lateral hypothalamic area (LHA)
- something to do with arcuate nucleus

57
Q

_______ neurons release neuropeptide Y

A

orexigenic
- feeding center

58
Q

Fill in the blanks.

A