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Gastrointestinal I > GI Physiology The Basics - Karius > Flashcards

GI Physiology The Basics - Karius Flashcards

1
Q

Enteric nervous system

A 
Intrinsic nervous system
Completely contained within the gut - esophagus to anus
Myenteric plexus  Submucosal plexus
-motility
-secretion
-hormone release
-blood flow
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2
Q

Submucosal plexus

A

In submucosa

Controls secretions, circulation and muscular is mucosae contraction

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3
Q

Myenteric Plexus

A

(aka Auerbach’s)
Between muscle layers
Controls motility

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4
Q

The 5 most common NTs of the enteric nervous system?

A

ACh - increases activity
VIP - increase secretion, decrease motility
Norepinephrine - decrease activity - especially motility
NO - major inhibitory NT of enteric NS
Opioids - primarily endorphins

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5
Q

What is the major inhibitory NT of enteric nervous system?

A

Nitric oxide - required to cause relaxation

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6
Q

2 diseases related to nitric oxide

A

Hirschsprungs disease - region tightly contracted, obstruction
Achalasia - LES doesn’t relax, swallowing painful

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7
Q

What enzyme is required for nitric oxide?

A

Nitric oxide synthase

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8
Q

What effect does sympathetics have on the GI system?

A

Decrease activity of intrinsic neurons
Depress most GI functions
-decrease blood, secretion, motility
-increase sphincter tone

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9
Q

What effect does parasympathetics have on the GI system?

A

Increase activity of intrinsic neurons
Excite most GI functions
-increase blood flow, secretion, motility
-relax sphincters

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10
Q

Local reflexes in the gut

A

Distension in stomach increases gastric motility

  • neurons that mediate are located in enteric NS
  • NO involvement of CNS or ANS
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11
Q

Long loop reflexes in the gut

A
  1. distension in the stomach
  2. relaxation in the colon
    “get ready, here comes food”
    Afferent to sympathetic ganglia, then back to gut
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12
Q

How do you name GI reflexes

A

First part of name - origin of the reflex

Second part of name - where the effect occurs

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13
Q

Explain the gastrocolic reflex

A

Origin - stomach (distension)
Effect occurs - colon (induces relaxation)
-long loop reflex

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14
Q

Longest reflexes in the gut

A 
Cell body in dorsal root ganglion (not enteric)
To CNS
Back to gut
Most are inhibitory
Ex. response to pain (surgery)
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15
Q

Which type of reflex involves the CNS?

A

Longest reflex

-stimulus may arise from other viscera

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16
Q

Gastrin

A

Pyloric glands - G cells - peptide hormone elicited by dissension
Increase acid secretion, motility, pancreatic enzyme secretion
Travels via blood

17
Q

Secretin

A

Peptide hormone
S cells of intestine
Presence of acid in duodenum
Travels via blood

18
Q

What is secretin’s main job?

A

Protection against acid

  • stomach - decrease gastrin, acid and motility
  • pancrease and liver - increase bicarbonate
19
Q

CCK-PZ

A 
Cholecystokinin-pancreozymin
I cells of intestine
Peptide hormone
Similar to gastrin
Presence of fats in duodenum
Travels via blood
20
Q

Major role of CCK-PZ?

A

Pancreas - increase enzyme secretion (pancreozymin)
Gall bladder - contraction of gall bladder (cholecystokinin)
Also acts in brain, liver - satiety

21
Q

Glucagon-like Peptide 1

A 
(GLP-1)
L cells of intestine
Peptide hormone
From proglucagon
Stimulus: nutrients, esp fats and dietary fiber in intestine
Travels via blood
22
Q

Job of Glucagon-like Peptide 1

A

Increase - insulin secretion

Decrease gastric acid and motility

23
Q

Glucagon-like Peptide 2

A 
(GLP-2)
L cells of intestine
Peptide hormone
From proglucagon
Stimulus - nutrients - esp fats and dietary fiber, intestinal injury
Travels via blood
24
Q

Which hormone is a trophic factor for intestine?

A

Glucagon-like Peptide 2
Growth of villi
Mucosal hyperplasia

25
Q

Motilin

A

Produced by stomach, small intestine, colon
Stimulus unknown - increases every 100 minutes between meals
Stimulates motility, especially the occurrence of the migrating motor complex

26
Q

What is the oxygen state of the villus and why?

A

It is hypoxic all the time - leads to short life span

O2 from the artery diffuses across to the venous blood (down gradient)

27
Q

GI blood flow

A

Venous blood - most to hepatic portal system, some back to heart
Sympathetic stimulation - vasoconstriction, may totally occlude
Parasympathetic - dilation

28
Q

P-glycoprotein

MDR-1 gene product

A

P = permeability
MDR = multi-drug resistance
Cells expressing this protein survived drug doses that were toxic/lethal to other cells
Function - remove drugs/other shit from cell to lumen (prevent absorption)

29
Q

What happens if there is less P-glycoprotein expression?

A

More drug in plasma

And vice versa

30
Q

P-glycoprotein polymorphisms are suggested in susceptibility to

A

IBD and colon cancer

Gastrointestinal I (25 decks)

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