L13 - Pain 2

Question 1

3 Types of Pain

Answer 1

1) Nociceptive pain - acute pain arising from threatened or actual damage to non-neural tissue
2) Inflammatory pain
3) Neuropathic pain - caused by lesion or disease of the somatosensory NS

Question 2

What are the less commonly known A-Beta fibres?

Answer 2

Low threshold - associated with touch and pressure and pain processing

Question 3

3 Types of dorsal horn neurons

Answer 3

1) Low threshold neurons
Respond only to innocuous stimulation e.g. light touch, pressure

2) Nociceptor specific (high threshold) neurons
Respond only to noxious stimuli, hyperalgesia

3) Wide dynamic range neurons
Responds to both noxious and innocuous stimuli
-Allodynia and hyperalgesia
-receive signals from multiple tissues including skin, viscera, muscles and joints

Question 4

What happens in neurons that are affected by Central Sensitization?

Answer 4

1) Increased spontaneous activity
2) Reduced thresholds or increased responsiveness to afferent inputs
3) Prolonged after-discharges to repeated stimulation
4) Expansion of the peripheral receptive fields of central neurons

Question 5

What condition occur when A-delta/C fibres OR nociceptive neurons are sensitized?

Answer 5

Hyperalgesia

Question 6

What condition occur when low threshold A-Beta fibres OR wide dynamic range neurons are sensitized?

Answer 6

Allodynia

Question 7

Do nociceptors synapse directly into the brain?

Answer 7

No - they have second order neurons that do

Question 8

WIND UP

a) What is wind-up generated by?
b) What does it require? (Not central sensitisation but contributes to it)
c) Effect on A-delta fibres?
d) Out of the 3 types of dorsal horn neurons - which does it affect? Is it LT or ST sensitization of dorsal horn neurons?

Answer 8

a) Repeated activation of C-fibre nociceptors leading to a progressive increase in perceived pain (e.g. doesn’t lower threshold but generates greater activity for the same stimulus)
b) It requires high freq input arriving at more than 1 impulse every 3 seconds
c) Response to A-delta fibre inputs remain unchanged
d) Characteristic of wide-dynamic range neurons (affects them more than nociceptive neurons). Short term sensitization (mins to hours)

Question 9

Glial cells and central sensitization - what is their role?

Answer 9

• Respond to increased input from peripheral nociceptors - e.g. during inflammation and neuropathy
• Change morphology and increase in number
• Release pro-nociceptive such as cytokines that affect dorsal horn neurons

Question 10

What does IL1Beta released by vascular endothelial cells do?

Answer 10

Induce COX-2 on neurons