B. Peripheral and central sensitisation

Question 1

What is the protective mechanism related to pain ?

Answer 1

Protective mechanism leads to:

• Reflex
• Avoidance behaviour

Question 2

What is the immediate motor response after noxious stimuli ?

Answer 2

Reflex

Question 3

What is the meaning of innocuous stimuli ?

Answer 3

Light touch

Question 4

What are the differences in pain experienced when inflammation sensitises the sensory system?

Answer 4

Innocuous pain becomes elicit pain
Response to noxious stimuli is enhances and prolonged
Threshold has lowered

Question 5

What consequences can hypersensitivity have on neuronal damage ?

Answer 5

• Mechanical trauma
• Metabolic disease such as diabetes
• Neurotoxic chemicals (chemotherapy)
• Inflection
• Tumour invasion
• Spinal cord injury
• Stroke

Nerve damage can carry painful message without any noxious stimuli

Question 6

What is the definition of allodynia ?

Answer 6

Pain in response to normally innocuous stimulus

Question 7

what is the definition of hyperalgesia ?

Answer 7

Pain in response to a noxious stimulus with an exaggerated response

Question 8

What is peripheral sensitisation?

Answer 8

• Nociceptor activation thresholds are lowered

- The nociceptor starts firing more and more and this is experienced as a pain

Question 9

What is central sensitisation?

Answer 9

• Spinal cord (and brain) pain neurons are changed (anatomically, physiologically) so that they show increased responsivness to peripheral input

Question 10

What happens when tissue damage and inflammation occurs ?

Answer 10

The chemical environment of nociceptor terminal changes

Many factors produced by numerous cell residing within or inflammatory into injured area

Generated an inflammatory soup

Question 11

What neurotransmitters are in the ‘soup’?

Answer 11

Peptide:
Substance p
CGRP
bradykinin

Lipids:
Prostaglandins 
Thromboxanes 
Leukatrienes 
Endocannabinoids 

Neurothrophins
Cytokines 
Chemokines 
Proteases
Protons

Question 12

How do these factors work ?

Answer 12

Factors bind to the receptor

Leads to depolarisation or alteration of the activation threshold.

This leads to increased nociceptor excitation

Question 13

How does the binding of prostaglandins change nociceptor excitability ?

Answer 13

Prostaglandin E2 binds to PGE2 receptor
Activates Gs G-protein
Activates adenylyl cyclase which converts ATP into cyclic AMP
Cyclic AMP activates protein kinase A
This facilitates voltage gates sodium channels
Changes nociceptor excitability