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Regulation of GI function I Flashcards

1
Q

What are the three principal control mechanisms of GI function?

A
  1. ) Endocrine
  2. ) Paracrine
  3. ) Neural
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2
Q

Comprised of specialized cells that secrete peptides into the blood

-act distally

A

Endocrine regulation

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3
Q

Comprised of specialized cells that secrete peptides into the interstitium

-act locally via diffusion

A

Paracrine regulation

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4
Q

Neural regulation occurs via both

A

Intrinsic and extrinsic pathways

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5
Q

A key regulator of the GI tract

A

ANS

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6
Q

The EXTRINSIC GI nervous system is made up of

A

Parasympathetic and sympathetic nerves

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7
Q

The INTRINSIC (enteric) GI nervous system is made up of the

A

Myenteric (Auerbach) and Submucosal (Meissner) Plexuses

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8
Q

Cells of the autonomic nervous system originate from the

A

Neural crest

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9
Q

All preganglionic nerves in the PNS release

A

ACh

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10
Q

ACh acts upon

A

Type N2 Nicotinic-ACh receptors

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11
Q

Type N2 receptors are considered to be

A

Ligand-gates ion channels

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12
Q

All postganglionic PNS nerves release

A

ACh

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13
Q

This ACh release by post ganglionic PNS nerves acts upon

A

ACh-Muscarinic receptors (G-protein coupled receptors)

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14
Q

Preganglionic fibers of the parasympathetic nervous system enter the GI tract and synapse with the

A

Enteric nervous system

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15
Q

The parasympathetic neurotransmitter for the myenteric and submucosal plexuses is

A

ACh

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16
Q

What are the three main functions that ACh serves as a regulator of GI function?

A
  1. ) Increases salivary secretions
  2. ) Stimulates GI tract secretions
  3. ) Stimulates intestinal motility
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17
Q

Which types of gastric secretion is stimulated by ACh?

A

Gastric acid and pancreatic acinar secretion (digestive enzymeS)

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18
Q

Medicines which aim to increase gut motility and secretion will often act as either

A

Cholinesterase inhibitors or ACh analogues

-i.e. they increase cholinergic stimuli

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19
Q

Carry non-nociceptive signals to the CNS

-i.e. don’t carry pain signals

A

Parasympathetic afferents

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20
Q

Distension sensed by mechanoreceptors activates the vago-vagal reflex which results in

A

Gastrin secretion which stimulates HCl and pepsinogen secretion

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21
Q

The enteric nervous system is also stimlated by

A

Distension

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22
Q

All preganglionic sympathetic nerves release ACh which acts on

A

N2-R

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23
Q

All post ganglionic sympathetic nerves in the GI tract release the neurotransmitter

A

Norepinephrine

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24
Q

Acts on G-protein coupled receptors

A

Norepinephrine

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25
Q

Postganglionic fibers of the sympathetic nervous system enter the GI tract and synapse with both the

A

Enteric nervous system as well as individual target cells

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26
Q

The sympathetic neurotransmitter for the myenteric and submucosal plexuses is

A

Norepinephrine

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27
Q

What is more important in GI function regulation, ACh or Norepinephrine?

A

ACh (by a lot)

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28
Q

What are the two main functions of norepi in GI regulation?

A
  1. ) Increases fluid reabsorption

2. ) decreases peristaltic activity and constricts sphincters

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29
Q

A VERY important regulator of vascular tone

A

Norepinephrine

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30
Q

Carry nociceptive (pain) signals to the CNS

A

Sympathetic afferents

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31
Q

During embryonic development, visceral structures were which type of structures?

A

Midline structures

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32
Q

Thus, visceral pain DOES NOT

A

Lateralize

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33
Q

Extrinsic control of the GI tract is via the

34
Q

Preganglionic PNS fibers synapse directly on

A

Enteric plexus

35
Q

Composed of 100 million neurons which are clustered into the submucosal and myenteric plexuses

A

Enteric nervous system

36
Q

Found in the small and large intestine only

A

Submucosal plexus

37
Q

Found in the GI tract from the esophagus to the rectum

A

Myenteric plexus

38
Q

What is the predominant function of the

  1. ) Myenteric plexus
  2. ) Submucosal plexus
A
  1. ) Motility

2. ) Secretion

39
Q

Has an identical response to distension of the GI tract or presence of bacterial endotoxin

-suggests a preprogrammed response

40
Q

In response to GI distension of bacterial endotoxin, the ENS does which two things?

A
  1. ) Stimulates profuse fluid and electrolyte secretion

2. ) Stimulates propulsive, coordinated, SMC contraction

41
Q

The primary neurotransmitter of the ENS

42
Q

What are 4 other neurotransmitters of the ENS?

A
  1. ) Norepi
  2. ) Vasoactive Intestinal Peptide
  3. ) Gastrin-releasing peptide
  4. ) Substance P
43
Q

A primary component of the non-cholinergic, non-adrenergic (NANC) nerve transmission

A

Vasoactive Intestinal Peptide (VIP)

44
Q

VIP is classified as an

A

Inhibitory neurotransmitter

45
Q

What are the two main functions of VIP in NANC neurons?

A
  1. ) Opposes normal smooth muscle tone

2. ) Relaxes GI smooth muscle

46
Q

Stimulates epithelial secretion and promotes fluid and bicarbonate secretion from bile duct cells

47
Q

A potent relaxer of smooth muscle, including the lower esophageal sphincter

48
Q

VIP is often packaged together with NO to cause

A

Vasodilation

49
Q

Results from a high resting lower esophageal pressure with failure to relax due to absent peristalsis and additional neuron loss

50
Q

In achalasia we see the loss of upper esophageal relaxation and the body of the esophagus

51
Q

Essentially, we can consider achalasia to be caused from the loss of

A

Inhibitory neurons (that would secrete VIP)

52
Q

Neuroendocrine tumor located in the pancreas, which is caused by excessive, unregulated VIP secretion

53
Q

Locates in ENS nerve terminals with receptors throughout the GI tract where it is the most potent stimulator of Gastrin release

A

Gastrin-releasing peptide (bombesin)

54
Q

Stimulates gastric acid secretion

55
Q

In addition to gastrin release, Gastrin-releasing peptide also stimulates

A

CCK release and enzyme-rich pancreatic secretions

56
Q

What are the two important NANC neurotransmitters?

A

VIP and Gastrin-releasing peptide (G-RP)

57
Q

Enteroendocrine cells are also known as

A

Argentaffin, APUD, and Neuroendocrine

58
Q

APUD stands for

A

Amine precursor uptake and decarboxylation

59
Q

Are NOT of neural crest origin but rather are derived from the endoderm

A

Enteroendocrine cells

60
Q

Hormone producing cells of the GI tract which are wide-spread in the mucosal lining and the glands

A

Enteroendocrine cells

61
Q

Enteroendocrine cells are essential for life and are detected by

A

Immunostaining or EM

62
Q

What are the 7 subpopulations of enteroendocrine cells?

A
  1. ) A (X-like) cells
  2. ) G cells
  3. ) D cells
  4. ) I Cells
  5. ) S cells
  6. ) L cells
  7. ) EC cells
63
Q

An example of an A cell secretion is

64
Q

An example of a G cell secretion is

65
Q

An example of a D cell secretion is

A

Somatostatin

66
Q

An example of an I cell secretion is

67
Q

An example of an S cell secretion is

68
Q

An example of an L cell secretion is

A

GLP-1 and GLP-2

69
Q

An example of an EC cell secretion is

70
Q

A cells are mainly located in the

71
Q

G cells are located in the

A

Stomach (antrum) and duodenum

72
Q

Located in the stomach (gastric corpus and antrum) and the small intestine

73
Q

Located in the proximal small intestine

A

I Cell and S Cell

74
Q

Located in the distal small intestine and colon

75
Q

Located in the stomach, small intestine, and large intestine

76
Q

Enteroendocrine cells extend neuropods that synapse with the

77
Q

Function to regulate water, electrolyte metabolism, and enzyme secretion

A

GI hormones

78
Q

GI hormones also regulate mucosal growth and

A

Gastrointestinal motility

79
Q

GI hormones stimulate the release of other

A

GI hormones

80
Q

Can be thought of as enteric sensors that release hormones and connect to the ENS

A

Enteroendocrine cells

81
Q

Synthesized as large molecules that undergo posttranslational processing

A

Enteroendocrine cells

82
Q

What are the two general families of enteroendocrine cells?

A
  1. ) Gastrin and CCK

2. ) Secretin and related molecules

GI (59 decks)

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