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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
Actions of GIP
- increase insulin secretion from pancreatic Beta cells | - decrease Gastric H+ secretion
26
What nucleus has the feeding center?
Lateral nucleus
27
What nucleus has the satiety center?
Ventromedial nucleus
28
What nucleus feeds information into the feeding and satiety center?
Arcuate nucleus
29
Where does most of the integration signaling regulating food intake and energy expenditure happen?
Arcuate nucleus
30
Explain the alpha-melanocortin (alpha-MSH) pathway
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
Explain the neuropeptide Y (NPY) pathway
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
Mutations in the POMC and MCR-4 genes can be linked to what disorder?
Obesity
33
Where is Ghrelin secreted?
By endocrine cells in the stomach
34
What does Ghrelin do in the hypothalamus?
Stimulates neurons that release NPY
35
List the things that Ghrelin increases
1) appetite 2) gastric motility 3) gastric acid secretion 4) adipogenesis
36
Where does insulin bind in the hypothalamus
Satiety and hunger centers
37
What does insulin do to NPY and POMC pathways, respectively
- inhibits | - stimulates
38
Actions of insulin
- decrease appetite | - increase metabolism
39
In diabetes mellitus type 1, decrease in insulin causes what?
Increase in food intake
40
What is CCK released by?
I cells in the duodenum
41
How does CCK elicit satiety?
- Acts on Vagal->NTS->hypothalamus circuit to decrease Ghrelin - Decrease gastric emptying which increases gastric distention
42
Where is PYY secreted from
EECs (L cells) of the ileum and colon following a meal
43
What does PYY bind to
Y2 receptors of the hypothalamus
44
What does PYY do in the hypothalamus
- Inhibits NPY neurons | - Releases inhibition of POMC neurons
45
What is a possible clinical relevance of PYY?
Potential appetite suppressor
46
Where is Leptin secreted?
Cells in adipose tissue and by endocrine cells in the stomach
47
What does Leptin do the the NPY and POMC pathways respectively
- inhibits | - stimulates
48
Describe the appetite suppressing actions of Leptin
- decreases appetite - increases metabolism - decreases Ghrelin release
49
Post ganglionic parasympathetics innervated what in the wall of the GI track?
Either the my enteric or sub mucosal plexus

Gastrointestinal (9 decks)

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