Pain

Question 1

Define ‘nociceptor’

Answer 1

Primary afferent neuron that responds specifically to noxious stimuli

Question 2

Which 2 fibres are nociceptors?

Answer 2

Unmyelinated small-diameter C fibres

Myelinated medium-diameter Adelta fibres

Question 3

What is the conduction speed of Adelta fibres and what is their purpose?

Answer 3

Fast

Signals injury, localisation of stimulus, reflex withdrawal

Question 4

What is the conduction speed of C fibres and what is their purpose?

Answer 4

Slow

Protection during healing

Question 5

What are the 2 types of C fibres?

Answer 5

Peptidergic

Non-peptidergic

Question 6

What are the roles of non-peptidergic C fibres?

Answer 6

Slow burning pain
Cause negative emotional response
Cause autonomic response

Question 7

What are the roles of peptidergic C fibres?

Answer 7

Release CGRP/SP in periphery

Promote inflammation and healing - neurogenic response

Question 8

Which receptors do peptidergic C fibres express?

Answer 8

trkA (NGF-sensitive)
TRPV1
TRPM8

Question 9

Which receptors do non-peptidergic C fibres express?

Answer 9

IB4
RET (GDNF-sensitive)
TRPV1
Nav1.9
P2X3

Question 10

Which fibres only detect mechanical stimuli?

Answer 10

Most Adelta

Question 11

Which fibres are polymodal?

Answer 11

Most C fibres

Question 12

What activates TRPV1?

Answer 12

> 43°C

Capsaicin

Question 13

What activates TRPA1?

Answer 13

<15°C

Question 14

What activates TRPM8?

Answer 14

Noxious and non-noxious stimuli

Question 15

Which type of C fibres are involved in peripheral sensitisation?

Answer 15

Peptidergic

Question 16

What is the process of peripheral sensitisation?

Answer 16

NGF binds to TrkA
Complex retrogradely transported to cell body in DRG
Increases TRPV1 transcription
Anterograde transport and insertion of TRPV1 channels
Reduced pain threshold at inflammation site