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Gastrointestinal > Introduction To GI Physiology > Flashcards

Introduction To GI Physiology Flashcards

1
Q

Synapses between pre and post ganglionic parasympathetic cells are what?

A

Nicotinic

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2
Q

What do sympathetic post ganglionic nerves innervated in the GI track?

A

Along with the myenteric and submucosal plexi, also directly innervated the smooth muscle and glands

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3
Q

Sympathetic innervation does what to sphincters?

A

Relaxation

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4
Q

Describe the path or track of the Vago-vagal reflex

A

Vagal Afferents –> Nodose ganglion –> Nucleus of the tractus solitarius (NTS) –> Vagal Efferent

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5
Q

What is the main peptide used in paracrine regulation of the GI track? Also name 1 more messenger molecule

A
  • Somatostatin

- Histamine

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6
Q

Molecules released through paracrine regulation are released by what cells?

A

Estero endocrine cells (EECs)

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7
Q

Somatostatin is secreted by _____ cells of the GI ________.

A

D; mucosa

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8
Q

What is the stimuli for release of somatostatin?

A

Decrease in luminal pH

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9
Q

What are the actions of somatostatin?

A
  • inhibit gastric H+ secretion - by Parietal cells or by inhibiting histamine or gastric which regulate parietal cells
  • inhibit secretion of other GI hormones
  • MAIN inhibitor
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10
Q

Where is somatostatin secreted outside of the GI tract?

A
  • hypothalamus

- delta cells of exocrine pancreas

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11
Q

Is Histamine a peptide signaler?

A

NO; it’s an amine

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12
Q

In the stomach, Histamine is stored and secreted by __________ cells in ___________ glands.

A
  • enterochromaffin - like (ECL)

- gastric

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13
Q

Histamine targets what cells?

A

Parietal

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14
Q

What is the action of histamine?

A

Stimulate acid production

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15
Q

Describe the path of an endocrine hormone secreted by the GI tract

A

Secretion –> portal circulation –> Liver – > systemic circulation –> Target cell

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16
Q

Name the stimuli for secretion of Gastrin

A
  • small peptides and a.a.
  • Distention of the stomach
  • Vagal stimulation (via GRP)
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17
Q

Name the stimuli for secretion of cholecystokinin (CCK)

A
  • small peptides and a.a.

- fatty acids

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18
Q

Name the stimuli for secretion of secretin

A
  • H+ in the duodenum

- fatty acids in the duodenum

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19
Q

Name the stimuli for secretion of Glucose-dependent insulinotropic peptide (GIP)

A
  • Fatty acids
  • a.a.
  • Oral Glucose
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20
Q

What are the actions of Gastrin

A
  • increase gastric H+ secretion
  • stimulates growth of gastric mucosa (RNA and DNA and such)
  • increase # of parietal cells
21
Q

Describe Zollinger-Ellison syndrome

A
  • increase circulating levels of Gastrin
  • increase acid secretion by parietal cells
  • hypertrophy of gastric mucosa
  • duodenal ulcers
  • steatorrhea (fat in feces because reduced absorptive abilities)
22
Q

Actions of CCK

A
  • Increase pancreatic enzyme secretion
  • increase pancreatic HCO3- secretion indirectly by affecting secretin
  • contraction of the gallbladder and relaxation of sphincter of Oddi
  • growth of exocrine pancreas and gallbladder (TROPHIC)
  • inhibits gastric emptying (protein and fat need more digestion time in the stomach)
  • can also act as a paracrine signal
23
Q

What are the two receptors for CCK?

A

CCK1 or CCKa: specific for CCK

CCKb: sensitivity for both Gastrin and CCK

24
Q

Actions of secretin

A
  • increase pancreatic HCO3-
  • increase biliary HCO3- secretion
  • decrease Gastrin H+ secretion
  • inhibits trophic effect of Gastrin on gastric mucosa
  • can also act as a paracrine signal
25
Q

Actions of GIP

A
  • increase insulin secretion from pancreatic Beta cells

- decrease Gastric H+ secretion

26
Q

What nucleus has the feeding center?

A

Lateral nucleus

27
Q

What nucleus has the satiety center?

A

Ventromedial nucleus

28
Q

What nucleus feeds information into the feeding and satiety center?

A

Arcuate nucleus

29
Q

Where does most of the integration signaling regulating food intake and energy expenditure happen?

A

Arcuate nucleus

30
Q

Explain the alpha-melanocortin (alpha-MSH) pathway

A

1) alpha-MSH released by pro-opiomelanocortin (POMC) neurons
2) binds to MCR-4 present in second order neurons
3) INHIBITS FOOD INTAKE AND INCREASES METABOLISM (ANOREXIGENIC)

31
Q

Explain the neuropeptide Y (NPY) pathway

A

1) hunger signals stimulate the release of NPY
2) NPY binds to Y1R
3) Neurons that release NPY also release agouti-related peptide (AGRP)
4) AGRP is an antagonist of MCR-4
5) INCREASE FEEDING BEHAVIOR & STORAGE OF CALORIES (OREXIGENIC)

32
Q

Mutations in the POMC and MCR-4 genes can be linked to what disorder?

A

Obesity

33
Q

Where is Ghrelin secreted?

A

By endocrine cells in the stomach

34
Q

What does Ghrelin do in the hypothalamus?

A

Stimulates neurons that release NPY

35
Q

List the things that Ghrelin increases

A

1) appetite
2) gastric motility
3) gastric acid secretion
4) adipogenesis

36
Q

Where does insulin bind in the hypothalamus

A

Satiety and hunger centers

37
Q

What does insulin do to NPY and POMC pathways, respectively

A
  • inhibits

- stimulates

38
Q

Actions of insulin

A
  • decrease appetite

- increase metabolism

39
Q

In diabetes mellitus type 1, decrease in insulin causes what?

A

Increase in food intake

40
Q

What is CCK released by?

A

I cells in the duodenum

41
Q

How does CCK elicit satiety?

A
  • Acts on Vagal->NTS->hypothalamus circuit to decrease Ghrelin
  • Decrease gastric emptying which increases gastric distention
42
Q

Where is PYY secreted from

A

EECs (L cells) of the ileum and colon following a meal

43
Q

What does PYY bind to

A

Y2 receptors of the hypothalamus

44
Q

What does PYY do in the hypothalamus

A
  • Inhibits NPY neurons

- Releases inhibition of POMC neurons

45
Q

What is a possible clinical relevance of PYY?

A

Potential appetite suppressor

46
Q

Where is Leptin secreted?

A

Cells in adipose tissue and by endocrine cells in the stomach

47
Q

What does Leptin do the the NPY and POMC pathways respectively

A
  • inhibits

- stimulates

48
Q

Describe the appetite suppressing actions of Leptin

A
  • decreases appetite
  • increases metabolism
  • decreases Ghrelin release
49
Q

Post ganglionic parasympathetics innervated what in the wall of the GI track?

A

Either the my enteric or sub mucosal plexus

Gastrointestinal (9 decks)

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