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GI-Final > Intro To GI Physiology-1/13/16 > Flashcards

Intro To GI Physiology-1/13/16 Flashcards

1
Q

List the functional layer of the GI tract:

A

Mucosa (epithelium, lamina propria, muscularis mucosae)
Submucosa (meissner’s plexus)
Muscularis layer (CIrcular muscle-Auerbach’s plexus-Long.Muscle)
Serosa or adventitia

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2
Q

The GI tract is innervated by the:

A

ANS and Enteric NS

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3
Q

Where does the extrinsic NS have cell bodies?

A

Located OUTSIDE the gut wall

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4
Q

Where does the intrinsic NS have cell bodies?

A

located WITHIN the wall of the gut

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5
Q

Describe the PARASYMPATHETIC NS for the gut

A

Via Vagus and Pelvic splanchnic nerves

Preganglionic nerve cell bodies are located in the brainstem or the Sacral SC

Postganglionic neurons lies in the wall of the organ (enteric neuron in the gut wall)

Synapse between pre- and post-ganglionic cells in nAChR’s

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6
Q

Describe the SYMPATHETIC NS for the gut

A

Via nerves that run between the SC and prevertebral ganglia & between these ganglia and the organs of the gut

Preganglionic EFFERENT fibers arises within the SC and end in the prevertebral ganglia

Postganglionic fibers from the prevertebral ganglia innervates the MYENTERIC and SUBMUCOSAL plexuses and other elements of ENS

Mostly, preganglionic EFFERENT fibers release Ach, while postganglionic EFFERENT nerves release NE

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7
Q

What type of PARASYMPATHETIC receptor is found in the Prevertebral ganglion?

What type of SYMPATHETIC receptor is found in the Prevertebral ganglion?

A

nAChr

nAChr

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8
Q

Where do you find a prevertebral ganglion in PARASYMPATHETICS?

Where do you find a prevertebral ganglion in SYMPATHETICS?

A

Wall of the organ within plexuses

Outside the GI tract

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9
Q

What type of postganglionic receptor is in PARASYMPATHETICS?

What type of postganglionic receptor is found in SYMPATHETICS?

A

mAChr

Alpha-adrenergic and/or beta-adrenergic

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10
Q

Describe the basic pathway of the ENS integrating center

A

Stimuli in the wall of the gut –> sensory neuron (ENS) –> Interneuron (ENS) –> Motor neuron (ENS) –> Output response

CNS can exert influence in the pathway

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11
Q

This type of cellular communication is local and the signals reach their target cells by diffusion over short distances

A

Paracrine regulation

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12
Q

Paracrine mediators are released by ___ cells or other sensing cells and use peptides (i.e., somatostatin) or other messenger molecules (histamine)

A

Enteroendocrine

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13
Q

This peptide is secreted by D cells (delta) of the GI mucosa and act to DECREASE luminal pH.

A

Somatostatin

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14
Q

Somatostatin acts to inhibit ___ secretion and is secreted ___ the GI tract

A

Gastric H+ and secretion of other GI hormones

Outside (hypothalamus or delta cells of exocrine pancreas)

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15
Q

In the stomach, ____ is stored and secreted by enterochromaffin-like (ECL) cells in gastric glands.

A

Histamine

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16
Q

What is the TARGET of histamine and its ACTION?

A

Target=Parietal cells

Action=stimulate acid production

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17
Q

This type of cell communication involves hormones being secreted in the portal circulation, passing through the liver, reaching systemic circulation, and finally binding to specific receptors on target cells

A

Endocrine regulation

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18
Q

Where is the site of secretion and stimuli of secretion for GASTRIN?

A

Site of secretion–> G cells of stomach

Stimuli of secretion –> Small peptides and AA’s, distention of stomach, and Vagal stimulation (via GRP)

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19
Q

Where is the site of secretion and stimuli of secretion for CCK?

A

Site of secretion –> I cells of duodenum and jejunum

Stimuli of secretion –> Small peptides and AA’s, fatty acids

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20
Q

Where is the site of secretion and stimuli of secretion for SECRETIN?

A

Site of secretion –> S cells of duodenum

Stimuli of secretion –> H+ in the duodenum, fatty acids in the duodenum

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21
Q

Where is the site of secretion and stimuli of secretion for GIP?

A

Site of secretion –> Duodenum and jejunum

Stimuli of secretion –> fatty acids, AA’s, oral glucose

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22
Q

What are the actions of GASTRIN?

A

Increase gastric H+ secretion

Stimulate growth of gastric mucosa

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23
Q

Zollinger-Ellison syndrome is a ____ tumor

A

Gastrin-secreting

Results in: increased circulating levels of gastrin, increased acid secretion by parietal cells, hypertrophy of gastric mucosa, duodenal ulcers, and steatorrhea

24
Q

What are the actions of CCK?

A

Increase pancreatic enzyme secretion
Increase pancreatic HCO3- secretion (not a direct effect, potentiates the effects of secretin)
Stimulate contraction of gallbladder and relaxation of sphincter of oddi
Stimulate growth of exocrine pancrease and gallbladder (trophic effect)
Inhibit gastric emptying
Can also act as a paracrine signal

25
Q

What are the actions of secretin?

A 
Increase pancreatic HCO3- secretion
Increase biliary HCO3- secretion
Decrease gastric H+ secretion
Inhibits trophic effect of gastrin on gastric mucosa
Can also act as a paracrine signal
26
Q

What are the actions of GIP?

A

Increase insulin secretion from pancreatic beta cells

Decrease gastric H+ secretion

27
Q

What would be more effective in increasing insulin secretion?
A-Oral glucose administration
Or
B) IV glucose administration

A

Oral glucose stimulates GIP, which stimulates insulin secretion, and also has direct stimulatory effects on Beta cells

28
Q

List the actions of Ach

A

Contraction of smooth muscle
Relaxation of sphincters
Increase: Salivary secretion, Gastric secretion, Pancreatic secretion

29
Q

List actions of NE

A

Relaxation of smooth muscle
Contraction of sphincters
Increase salivary secretion

30
Q

List actions of Vasoactive Intestinal Peptide (VIP)

A

Relaxation of smooth muscle

Increase: intestinal secretion, pancreatic secretion

31
Q

List actions of Gastrin-releasing peptide (GRP)

A

Increase gastrin secretion

32
Q

List actions of Enkephalins

A

Contraction of smooth muscle

Decrease intestinal secretion

33
Q

What are actions of Neuropeptide Y?

A

Relax smooth muscle

Decrease intestinal secretion

34
Q

What are actions of Substance P?

A

Contract smooth muscle

Increase salivary secretion

35
Q

List the neuronal centers of the hypothalamus that participate in the regulation of food intake:

A 
Lateral nucleus
Ventromedial nucleus
Paraventricular nucleus
Dorsomedial nucleus
Arcuate nucleus
36
Q

This neuronal center is the “feeding center”

This neuronal center is the “satiety center”

A

Lateral nucleus

Ventromedial nucleus

37
Q

Most of the integration signaling regulating food intake and energy expenditure happens in the ____

A

Arcuate nucleus

38
Q

Diagram the alpha-melanocortin pathway

A

Alpha-MSH released by POMC neurons –> alpha-MSH binds to MCR-4 present in 2nd-order neurons –> INHIBITS FOOD INTAKE AND INCREASES METABOLISM (ANOREXIGENIC)

Insulin, leptin, and CCK act as stimulators of POMC neurons by binding to LepR on POMC neurons

39
Q

Diagram the Neuropeptide Y pathway

A

Hunger stimulates the release of NPY –> NPY binds to Y1r of PVN neuron –> Neurons that release NPY also release Agouti-related peptide (AGRP) –> AGRP is antagonist of MCR-4 –> INCREASE FEEDING BEHAVIOR AND STORAGE OF CALORIES (OREXIGENIC)

  • Ghrelin is a stimulant of AGRP/NPY neurons
  • Insulin, leptin, CCK inhibit AGRP/NPY neurons
40
Q

Peptides that stimulate the alpha-MSH pathway ____ the NPY system

AGRP released from the NPY pathway is an antagonist of ___

A

Inhibit

MCR-4

41
Q

A patient who has an inhibitory mutation of POMC and MCR-4 genes will likely be predisposed to___

A

Obesity

42
Q

___ is secreted mainly by endocrine cells in the stomach, binds to GH secretagogue receptors, and stimulates neurons that release NPY in the hypothalamus

A

Ghrelin

43
Q

What are the actions of ghrelin?

A

Increase: Appetite, gastric motility, gastric acid secretion, adipogenesis, insulin secretion

Appears to initiate the feeding response

44
Q

___ binds to receptors in satiety and hunger centers within the hypothalamus (POMC and NPY systems), inhibits NPY pathway and stimulates POMC pathway

A

Insulin

45
Q

What are actions of insulin?

A

Decrease appetite

Increase metabolism

46
Q

What does insulin do to the NPY and POMC pathways?

A

Inhibits NPY, Stimulates POMC

47
Q

In patients with Type 1 DM, there is an ___ in food intake associated with ___ insulin

A

Increase

Decreased

48
Q

___ is released by I cells in the duodenum and elicits satiety

A

CCk

49
Q

How does CCK elicity satiety (pathway)?

A

Acts on vagal –> NTS –> hypothalamus circuit –> DECREASES ghrelin

Decreases gastric emptying –> INCREASES gastric distention

50
Q

___ is released by EECs (L cells) of the ileum and colon following a meal and has the potential as an appetite suppressor

A

PPY

51
Q

Describe the PPY pathway

A

PPY released by EECS of ileum and colon after a meal –> Binds to Y2 receptors of the hypothalamus (inhibits NPY neurons, releases inhibition of POMC neurons)

52
Q

___ is secreted by cells in adipose tissue and by endocrine cells in the stomach and is an appetite suppressing hormone

A

Leptin

53
Q

Describe the leptin pathway

A

Leptin secreted by cells in adipose tissue and by endocrine cells in stomach –> binds to receptors in satiety & hunger centers in the hypothalamus (POMC & NPY systems –> Inhibits NPY pathway, stimulates POMC pathway

Appears to be part of - feedback system for regulation of food intake

54
Q

Describe the effect of Leptin on the following:
A) appetite
B) metabolism
C) ghrelin release

A

A) decrease
B) increase
C) decrease

55
Q

What are the main functions of the GI tract?

A

Digestion and absorption of nutrients
Motility
Secretions

GI-Final (9 decks)

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