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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
Postganglionic fibers of the sympathetic nervous system enter the GI tract and synapse with both the
Enteric nervous system as well as individual target cells
26
The sympathetic neurotransmitter for the myenteric and submucosal plexuses is
Norepinephrine
27
What is more important in GI function regulation, ACh or Norepinephrine?
ACh (by a lot)
28
What are the two main functions of norepi in GI regulation?
1. ) Increases fluid reabsorption | 2. ) decreases peristaltic activity and constricts sphincters
29
A VERY important regulator of vascular tone
Norepinephrine
30
Carry nociceptive (pain) signals to the CNS
Sympathetic afferents
31
During embryonic development, visceral structures were which type of structures?
Midline structures
32
Thus, visceral pain DOES NOT
Lateralize
33
Extrinsic control of the GI tract is via the
ANS
34
Preganglionic PNS fibers synapse directly on
Enteric plexus
35
Composed of 100 million neurons which are clustered into the submucosal and myenteric plexuses
Enteric nervous system
36
Found in the small and large intestine only
Submucosal plexus
37
Found in the GI tract from the esophagus to the rectum
Myenteric plexus
38
What is the predominant function of the 1. ) Myenteric plexus 2. ) Submucosal plexus
1. ) Motility | 2. ) Secretion
39
Has an identical response to distension of the GI tract or presence of bacterial endotoxin -suggests a preprogrammed response
ENS
40
In response to GI distension of bacterial endotoxin, the ENS does which two things?
1. ) Stimulates profuse fluid and electrolyte secretion | 2. ) Stimulates propulsive, coordinated, SMC contraction
41
The primary neurotransmitter of the ENS
ACh
42
What are 4 other neurotransmitters of the ENS?
1. ) Norepi 2. ) Vasoactive Intestinal Peptide 3. ) Gastrin-releasing peptide 4. ) Substance P
43
A primary component of the non-cholinergic, non-adrenergic (NANC) nerve transmission
Vasoactive Intestinal Peptide (VIP)
44
VIP is classified as an
Inhibitory neurotransmitter
45
What are the two main functions of VIP in NANC neurons?
1. ) Opposes normal smooth muscle tone | 2. ) Relaxes GI smooth muscle
46
Stimulates epithelial secretion and promotes fluid and bicarbonate secretion from bile duct cells
VIP
47
A potent relaxer of smooth muscle, including the lower esophageal sphincter
VIP
48
VIP is often packaged together with NO to cause
Vasodilation
49
Results from a high resting lower esophageal pressure with failure to relax due to absent peristalsis and additional neuron loss
Achalasia
50
In achalasia we see the loss of upper esophageal relaxation and the body of the esophagus
Dilates
51
Essentially, we can consider achalasia to be caused from the loss of
Inhibitory neurons (that would secrete VIP)
52
Neuroendocrine tumor located in the pancreas, which is caused by excessive, unregulated VIP secretion
VIPoma
53
Locates in ENS nerve terminals with receptors throughout the GI tract where it is the most potent stimulator of Gastrin release
Gastrin-releasing peptide (bombesin)
54
Stimulates gastric acid secretion
Gastrin
55
In addition to gastrin release, Gastrin-releasing peptide also stimulates
CCK release and enzyme-rich pancreatic secretions
56
What are the two important NANC neurotransmitters?
VIP and Gastrin-releasing peptide (G-RP)
57
Enteroendocrine cells are also known as
Argentaffin, APUD, and Neuroendocrine
58
APUD stands for
Amine precursor uptake and decarboxylation
59
Are NOT of neural crest origin but rather are derived from the endoderm
Enteroendocrine cells
60
Hormone producing cells of the GI tract which are wide-spread in the mucosal lining and the glands
Enteroendocrine cells
61
Enteroendocrine cells are essential for life and are detected by
Immunostaining or EM
62
What are the 7 subpopulations of enteroendocrine cells?
1. ) A (X-like) cells 2. ) G cells 3. ) D cells 4. ) I Cells 5. ) S cells 6. ) L cells 7. ) EC cells
63
An example of an A cell secretion is
Ghrelin
64
An example of a G cell secretion is
Gastrin
65
An example of a D cell secretion is
Somatostatin
66
An example of an I cell secretion is
CCK
67
An example of an S cell secretion is
Secretin
68
An example of an L cell secretion is
GLP-1 and GLP-2
69
An example of an EC cell secretion is
5-HT
70
A cells are mainly located in the
Stomach
71
G cells are located in the
Stomach (antrum) and duodenum
72
Located in the stomach (gastric corpus and antrum) and the small intestine
D cell
73
Located in the proximal small intestine
I Cell and S Cell
74
Located in the distal small intestine and colon
L Cell
75
Located in the stomach, small intestine, and large intestine
EC Cell
76
Enteroendocrine cells extend neuropods that synapse with the
ENS
77
Function to regulate water, electrolyte metabolism, and enzyme secretion
GI hormones
78
GI hormones also regulate mucosal growth and
Gastrointestinal motility
79
GI hormones stimulate the release of other
GI hormones
80
Can be thought of as enteric sensors that release hormones and connect to the ENS
Enteroendocrine cells
81
Synthesized as large molecules that undergo posttranslational processing
Enteroendocrine cells
82
What are the two general families of enteroendocrine cells?
1. ) Gastrin and CCK | 2. ) Secretin and related molecules

GI (59 decks)

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