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Flashcards in GI Physiology The Basics - Karius Deck (30)
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1

Enteric nervous system

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

2

Submucosal plexus

In submucosa
Controls secretions, circulation and muscular is mucosae contraction

3

Myenteric Plexus

(aka Auerbach's)
Between muscle layers
Controls motility

4

The 5 most common NTs of the enteric nervous system?

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

5

What is the major inhibitory NT of enteric nervous system?

Nitric oxide - required to cause relaxation

6

2 diseases related to nitric oxide

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

7

What enzyme is required for nitric oxide?

Nitric oxide synthase

8

What effect does sympathetics have on the GI system?

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

9

What effect does parasympathetics have on the GI system?

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

10

Local reflexes in the gut

Distension in stomach increases gastric motility
-neurons that mediate are located in enteric NS
-NO involvement of CNS or ANS

11

Long loop reflexes in the gut

1. distension in the stomach
2. relaxation in the colon
"get ready, here comes food"
Afferent to sympathetic ganglia, then back to gut

12

How do you name GI reflexes

First part of name - origin of the reflex
Second part of name - where the effect occurs

13

Explain the gastrocolic reflex

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

14

Longest reflexes in the gut

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

15

Which type of reflex involves the CNS?

Longest reflex
-stimulus may arise from other viscera

16

Gastrin

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

17

Secretin

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

18

What is secretin's main job?

Protection against acid
-stomach - decrease gastrin, acid and motility
-pancrease and liver - increase bicarbonate

19

CCK-PZ

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

20

Major role of CCK-PZ?

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

21

Glucagon-like Peptide 1

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

22

Job of Glucagon-like Peptide 1

Increase - insulin secretion
Decrease gastric acid and motility

23

Glucagon-like Peptide 2

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

24

Which hormone is a trophic factor for intestine?

Glucagon-like Peptide 2
Growth of villi
Mucosal hyperplasia

25

Motilin

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

What is the oxygen state of the villus and why?

It is hypoxic all the time - leads to short life span
O2 from the artery diffuses across to the venous blood (down gradient)

27

GI blood flow

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

28

P-glycoprotein
(MDR-1 gene product)

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

What happens if there is less P-glycoprotein expression?

More drug in plasma
And vice versa

30

P-glycoprotein polymorphisms are suggested in susceptibility to

IBD and colon cancer