471-477. Aches and pains: physiological experiment

Question 1

What is the white reaction?

Answer 1

The first reaction to appear after mild tissue damage

It is an area of blanching which extends out a few mm from the side of the track

Question 2

What are the 3 components of the triple response?

Answer 2

Red reaction
Wheal
Flare

Question 3

What is the red reaction and what causes it?

Answer 3

The red line that immediately appears at the site of mild injury due to direct vasodilation (mediated by histamine)

Question 4

What is the wheal and what causes it?

Answer 4

Slight oedema at the site of injury - mediated by histamine

Question 5

What is the flare in the triple response and what causes it?

Answer 5

An ill-defined erythema surrounding the site of injury - mediated by the “axon reflex”

Question 6

During the period of peripheral hypersensitisation (hyperalgesia), why is the region with oedema (wheal) less sensitive than the others?

Answer 6

Oedema creates more space between the skin and the free nerve endings

Question 7

Why would infiltrating the skin with local anaesthetic prevent flare from occuring?

Answer 7

The anaesthetic would prevent the propagation of action potentials along the terminal branches of the nociceptive afferents

Question 8

What is ischaemic pain?

Answer 8

The pain associated with a lack of adequate blood supply to active tissue