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Physiology Exam 3 > Lecture 2: Gastrointestinal Regulatory Substances > Flashcards

Lecture 2: Gastrointestinal Regulatory Substances Flashcards

1
Q

Where are GI peptide-hormones released?

A

Endocrine cells of GIT

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2
Q

What is the route taken by GI peptide-hormones?

A

Portal circulation, liver, systemic circulation, target cells

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3
Q

Where is the target located for GI peptide-hormones?

A

Could be GIT or somewhere else

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4
Q

Where are GI paracrines released?

A

Endocrine cells of GIT

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5
Q

What is the route taken by GI paracrines?

A

Only need to diffuse short distance through interstitial fluid, or carried short distance in capillaries

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6
Q

What is the target of GI paracrines/where do they act?

A

Act locally and do not enter circulation

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7
Q

Do GI paracrines enter circulation?

A

No

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8
Q

Where are GI neurocrines synthesized?

A

In cell bodies of GI neurons

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9
Q

What causes the release of GI neurocrines?

A

Action potentials

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10
Q

Where is gastrin secreted and what by?

A

G cells in stomach

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11
Q

Which gastrin is secreted between meals at low basal levels?

A

Big gastrin

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12
Q

Which gastrin is secreted in response to a meal and is responsible for distention of stomach, presence of AA and peptides?

A

Little gastrin

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13
Q

What is the stimulus for secretion of gastrin?

A

Local vagal reflex

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14
Q

How does local vagal reflex act to cause release of gastrin?

A

Gastrin releasing peptide is released from vagal nerves on to G cells

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15
Q

Which of the following are functional effect of gastrin?
a. Secretion of bicarbonate from pancreas
b. Promotes hydrogen ion secretion by gastric parietal cells
c. Stimulates growth of gastric mucosa
d. Stimulates secretion of biliary HCO3
e. Increases gastric motility

A

B, C, E

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16
Q

What inhibits the release of gastrin?

A

Low gastric pH (don’t need anymore H+ secretion) AND somatostain

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17
Q

What is cholecystokinin (CCK) secreted by?

A

I cells by duodenal and jejunal mucosa

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18
Q

What is CCK secreted in response to?

A

Presence of fatty acids, amino acids, peptides

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19
Q

Name the 5 functional effects of CCK

A
  1. Contraction of gallbladder (ejects bile into lumen and small intestine to emulsify fat)
  2. Secretion of pancreatic enzymes (lipases going to digest lipids/fats; amylase digests starch; proteases digest proteins)
  3. Secretion of bicarbonate from pancreas (need to increase pH of digests entering small intestine)
  4. Growth of exocrine pancreas (insulin) and gallbladder
  5. Inhibition of gastric emptying: increase gastric emptying time, allow adequate time for digestion and absorption
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20
Q

Where is secretin secreted and what by?

A

S cells of duodenum

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21
Q

What is secretin secreted in response to?

A

Secreted in response to H ions and fatty acids presence in SI

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22
Q

Which of the following are functional effects of secretin?
a. Stimulates secretion of pancreatic and biliary HCO3
b. Increases gastric motility
c. Stimulates insulin secretion
d. Inhibits gastrin release from G cells in stomach

A

Answer: A and D

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23
Q

Why does secretin inhibit gastrin release from G cells in stomach?

A

Because gastrin release is inhibited by low gastric pH, secretin lowers gastric pH with HCO3

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24
Q

Where is gastric inhibitory peptide (GIP) secreted and what by?

A

Secreted by K cells of duodenum and jejunum

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25
Q

What is GIP secreted in response to?

A

Glucose, amino acids, fatty acids

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26
Q

Which of the following are functional effects of GIP?
a. Oral glucose load stimulates (intravenous does not)
b. Growth of exocrine pancreas
c. Increase gastric motility
d. Stimulates insulin secretion
e. Inhibits gastric H ion secretion and gastric emptying

A

A, D, E

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27
Q

Where is motilin secreted?

A

Upper duodenum

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28
Q

What is the stimulus for motilin secretion?

A

Fasting

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29
Q

Functional effects of motilin

A

Increases GI motility, initiates interdigestive myelectric complexes at 90 minute intervals, triggers peristaltic waves, indigestive substances + bacteria

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30
Q

Where is pancreatic polypeptide secreted?

A

Pancreas

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31
Q

What is pancreatic polypeptide secreted in response to?

A

Ingestion of carbs, proteins, lipids

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32
Q

What is the functional effect of pancreatic polypeptide?

A

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

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33
Q

What is enteroglucagon secreted by?

A

Interstitial cells

34
Q

What is enteroglucagon secreted in response to?

A

Decreased blood glucose

35
Q

What are the functional effects of enteroglucagon?

A

Stimulates the liver to increase glycolysis (breakdown of glucose store in liver) and gluconeogenesis (makes glucose from glycogenic AA and glycerol)

36
Q

What is glycolysis?

A

Breakdown of glucose stored in liver

37
Q

What is gluconeogenesis?

A

Making glucose from glycogenic amino acids and glycerol

38
Q

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

A

Secreted by L cells of SI

39
Q

What is Glucagon-like-peptide-1 (GLP-1) secreted in response to?

A

Nutrient ingestion

40
Q

Which of the following are functional effects of GLP-1?
a. Stimulates insulin secretion from pancreatic beta cells
b. Decreases gastric emptying
c. Inhibits glucagon secretion
d. Inhibits appetite

A

A, B, C, D

41
Q

Where is somatostain secreted and what by?

A

D cells of GI mucosa

42
Q

What is somatostatin released in response to?

A

Decreased luminal pH

43
Q

Which of the following are functional effects of somatostain?
a. Decreases gastric emptying
b. Inhibits secretion of other GI hormones and gastric H ion secretion
c. Inhibits glucagon secretion
d. Inhibits appetite

44
Q

Which of the paracrines is responsible for major inhibitory actions in the GIT?

A

Somatostatin

45
Q

Where is histamine secreted?

A

H ion secreting area of stomach

46
Q

What are the functional effects of histamine?

A

Stimulates H ion secretion by gastric parietal cells

47
Q

Acetylcholine is a

A

Neurotransmitter

48
Q

What type of neurons is acetylcholine secreted by?

A

Cholinergic neurons

49
Q

What are the functional effects of Ach?

A

Contraction of smooth muscle in wall
Relaxation of sphincters
Increases salivary secretion
Increases gastric secretion
Increases pancreatic secretion

50
Q

From what neurons is norepinephrine secreted?

A

Adrenergic

51
Q

What are the functional effects of norepinephrine?

A

Relaxation of smooth muscle in wall
Contraction of sphincters
Increases salivary secretion

52
Q

What neurons secrete VIP? (type and location)

A

Postganglionic non-cholinergic parasympathetic neurons
Neurons of mucosa and smooth muscle

53
Q

What are the functional effects of VIP?

A

Relaxation of smooth muscle
Increases intestinal secretion
Increases pancreatic secretion

54
Q

What neurons secrete GRP? (Type and location)

A

Postganglionic non-cholinergic parasympathetic neurons
Neurons of gastric mucosa

55
Q

What are the functional effects of GRP?

A

Increases gastrin secretion

56
Q

What neurons secrete enkephalins? (type and location)

A

Postganglionic non-cholinergic parasympathetic neurons
Neurons of mucosa and smooth muscle

57
Q

What are the functional effects of enkephalins?

A

Contraction of smooth muscle
Decreases intestinal secretion

58
Q

What neurons secrete neuropeptide Y? (type and location)

A

Postganglionic non-cholinergic parasympathetic neurons
Neurons of mucosa and smooth muscle

59
Q

What are the functional effects of neuropeptide Y?

A

Relaxation of smooth muscle
Decreases intestinal secretion

60
Q

What neurons secrete Substance P? (type and location)

A

Postganglionic non-cholinergic parasympathetic neurons
Co-secreted with Ach

61
Q

Functional effects of Substance P

A

Contraction of smooth muscle
Increases salivary secretion

62
Q

Name the GI-peptide hormones

A

Gastrin, cholecystokinin, secretin, gastric inhibitory peptide

63
Q

Name the candidate hormones

A

Motilin, pancreatic polypeptide, enteroglucagon, glucagon-like-peptide

64
Q

Name the GI paracrines

A

Somatostatin, histamine

65
Q

Name the GI neurocrines that are neurotransmitters

66
Q

Name the GI neurocrines that are neuromodulators

A

VIP, Gastrin-releasing-peptide, enkephalins, neuropeptide Y, substance P

67
Q

What is the action of the satiety center?

A

Inhibits appetite even in presence of food

68
Q

Where is the satiety center located?

A

Ventromedial nucleus (VPN) if hypothalamus

69
Q

Why type of neurons release pro-opiomelanocortin which decreases appetite?

A

Anorexigenic neurons

70
Q

What provides feeding info to both of the centers?

A

Arcuate nucleus

71
Q

What effect does leptin have?

A

Stimulates anorexigenic neurons and inhibits orexigenic neurons which decreases appetite

72
Q

What effect does insulin have?

A

Arcuate effects to decrease appetite

73
Q

What effect does GLP-1 have?

A

Decreases appetite

74
Q

What effect does Peptide YY have?

A

Decreases appetite by direct effect on hypothalamus and inhibits ghrelin secretion

75
Q

Where is the feeding center located?

A

Lateral hypothalamic area

76
Q

What neurons are associated with the feeding center?

A

Orexigenic neurons

77
Q

What do orexigenic neurons release?

A

Neuropeptide Y, which increases appetite

78
Q

What is ghrelin released by?

A

Gastric cells

79
Q

What effect does ghrelin have?

A

Stimulates appetite

80
Q

When is ghrelin secreted?

A

Just before ingestion of meal, starvation, and weight loss

Physiology Exam 3 (13 decks)

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