1.16 Pain

Question 1

Describe the characteristics of an A delta pain fibre…

Answer 1

• 1-5 micrometers
• Thin myelination
• Fast conduction speed - 20m/s
• SHarp, fast pain
• Responds to mechanical stimulation, painful heat/cold

Question 2

Describe the characteristics of a C pain fibre…

Answer 2

• 2.5 micrometers
• No myelination 
• 2m/s - slow 
• Dull slow ache 
• Same as Ad plus substances from damaged tissue
(multimodal)

Question 3

What are the different Rexed’s Laminae?

Answer 3

I = Marginal Zone 
II/III = Substantia Gelatinosa 
IV-VI = Nucleus proprius

Question 4

Where do the pain fibres synapse? And where do they ascend to after?

Answer 4

A delta - synapse lamina 1&5
C fibre - synapse lamina 1&2

Lamina 4,5,6 -> Thalamus anterolateral tract

Question 5

Define allodynia…

Answer 5

When peripheral sensitisation occurs, threshold lowers for non-noxious stimuli

Question 6

Define hyperalgesia…

Answer 6

When peripheral sensitisation occurs, threshold lowers and responsiveness increases for noxious stimuli

Question 7

What is central sensitisation?

Where can this occur?

Answer 7

Sensitisation in the spinal cord due to a change in the post synaptic neurone.
• Spinal Cord (lamina I and V neurones)
• Thalamus
• Amygdala
• Anterior cingulate cortex.