Enteric nervous system

Question 1

Enteric nervous system

Answer 1

part of peripharal but is mostly autonomous

Question 2

What does the ENS do ?

Answer 2

it coordinates smooth muscle in the gut and regulate digestive secretions without the input of the CNS

Question 3

Why is the ENS called the second brain

Answer 3

extensive and came earlier in evolution

Question 4

How much of human serotonin is in the gut?

Answer 4

90%

Question 5

Why study the ENS

Answer 5

better understanding of GI disorders but also helps understand the CNS

Question 6

Prevalence of IBS

Answer 6

17% in UK

Question 7

What percent of those with diabetes have GI tract symptoms?

Answer 7

70%

Question 8

Which CNS disorders have been linked to the ENS?

Answer 8

alzheimers, parkinsons and ALS

Question 9

What are the two sheets of neurons called in the ENS

Answer 9

plexus

Question 10

Myenteric plexus

Answer 10

• lies between muscle layers
• Controls gut motility which makes sense as it is sandwiched between two muscle layers.
• Contains both excitatory and inhibitory motor neurons
• Interneurons are called either ascending (towards mouth) or descending (towards anus)

Question 11

IPANS

Answer 11

intrinsic primary afferent neurons

Question 12

Submucosal plexus

Answer 12

• sits beneath the mucosa
• This regulates digestive secretions and interacts with blood vessels to regulate water balance.

Question 13

What do each plexus have?

Answer 13

ganglia (groups of neurons) and internodal strands (connections between ganglia).

Question 14

Cells of ENS mucosa

Answer 14

enterochromaffin cells and immune cells

Question 15

What are motor patterns in the ENS for?

Answer 15

Mixing food and transportation
- peristalsis
- accommodation
- migrating motor complex

Question 16

Where does peristalsis occur

Answer 16

in the oesophagus

Question 17

What is peristalsis

Answer 17

Contraction of smooth muscle behind food - excitatory ascending pathway

Relaxation of smooth muscle in front of food - inhibitory descending pathway

Question 18

where else does peristalsis occur

Answer 18

small and large intestine but not to propel food

Question 19

Accommodation

Answer 19

occurs in the upper area of the stomach and is triggered by distention of the lower oesophagus by food bolus

Question 20

inhibitory vagovagal reflex

Answer 20

to increase relaxation in stomach

Question 21

explain Inhibitory vagovagal reflex

Answer 21

distention detected by mechanorecptors > vagus nerve takes signal to CNS and back > release of vip in myenteric plexus > smooth muscle relaxed > increased volume of orad region

Question 22

Migrating motor complex

Answer 22

sweeps away the extras

Question 23

Migrating motor complex is

Answer 23

high amplitude, rhythmic, propogating waves for slow transit.

Question 24

How does MMC occur

Answer 24

spontaneously or evoked by mucosal stimulation or circumferential stretch

Question 25

How do you study CMMC

Answer 25

isolate colon, insert pellet with stick and look at motor activity on the pellet

Question 26

How is serotonin synthesised

Answer 26

tryptophan > (via tryptophan hydroxylase) 5-hydroxytryptophan > (via aromatic amino acid decarboxylase) 5-HT

Question 27

What is ondansetron

Answer 27

5-HT3 receptor blocker and when this was appled to the colon it inhibited the CMMC

Question 28

5-HT3R in ENS

Answer 28

expressed on the IPANS and intiates the CMMC

Question 29

5-HT7R in ENS

Answer 29

expressed on IPANS and generates the CMMC within the ENS

Question 30

5-HT4 in ENS

Answer 30

mediates the spread of CMMC

Question 31

5-HT1a In the ENS

Answer 31

regulates the CMMC

Question 32

What is CMMC

Answer 32

Colonic migrating motor complex

Question 33

What are the characteristics of IBS

Answer 33

abdominal pain, discomfort and variable bowl movements

Question 34

Cause of IBS

Answer 34

unclear, stress maybe, food intolerences maybe

Question 35

What was thought for IBS-C

Answer 35

has decreased 5-HT levels and dysfunctional TPH1

Question 36

What was thought for IBS-D

Answer 36

increased 5-HT and 5-HT3 receptor levels reduced SERT activity

Question 37

What do both IBS groups have

Answer 37

had less 5-HT and TPH and SERT

Question 38

To treat IBS-D

Answer 38

5-HT3 receptor agonists can be used to inhibit the activation and sensitivity of IPANS to reduce HAPCs

Question 39

IBS-D drugs

Answer 39

alosteron and ondansetron improve the stool consistancy and reduce frequency and urgency of needing the toilet but the side effect was constipation

Question 40

Underdeveloped IBS-D drug

Answer 40

LX-1031 was developed as a THP1 inhibtor by reducing 5-HT levels by disrupting its synthesis. There has been no work on this since early 2010s.

Question 41

Treatment of IBS-C

Answer 41

SSRI provide releif but also cause nausea, diarrhoea, weight gain and sexual dysfunction

Question 42

Drug for IBS-C

Answer 42

Tehaserod is a #5-HT4 agonist and acts directly on the myenteric plexus. This has been linked to increased heart attack and strokes.