3 – Plasticity of Pain Sensation

Question 1

Pain hypersensitivity

Answer 1

• State in which MORE pain is experience for a particular injury
• PROTECTIE: allows injured area to be protected until it has healed

Question 2

Characteristics of pain hypersensitivity

Answer 2

-hyperalgesia
-allodynia
-spontaneous pain (neuropathic pain)

Question 3

Hyperalgesia

Answer 3

-increased responsiveness to a noxious stimulus
o Ex. hit an elbow that is already bruised

Question 4

Allodynia

Answer 4

-pain experienced in response to a normally NON-noxious stimulus
o Ex. humans with SC injuries, can think wearing clothes is painful

Question 5

When does hypersensitivity occur? (2 general conditions)

Answer 5

1. Tissue inflammation=inflammatory pain
2. Damage to the NS (CNS or PNS) = neuropathic pain

Question 6

Tissue inflammation=inflammatory pain

Answer 6

a. Local disruption to tissues (ex. hemorrhage, inflammation)
1. Peripheral sensitization
2. Central sensitization

Question 7

1. Peripheral sensitization

Answer 7

a. Increased excitability of nociceptors when exposed to inflammatory mediators
i. How? Lower threshold for activation of ion channel receptors in nociceptor terminal membrane
ii. Net result? Increase firing frequency of nociceptors

Question 8

2. Central sensitization

Answer 8

i. Increased excitability of spinal pain relay neurons, initiated by sustained firing of nociceptors
1. How? Increased efficacy of the synapse between nociceptors and pain relay neurons
2. Net result? Lower firing threshold in pain relay neurons
3. *WINDUP PAIN: may need more medication depending on the timing

Question 9

2. Damage to the NS (CNS or PNS) = neuropathic pain

Answer 9

a. Less common
b. MALADAPTIVE RESPONSE
i. NS has tried to make connections and repairs but does NOT get it right = inappropriate perception of pain
c. NOT temporary
i. Can be long lasting or permanent =’learned pain’

Question 10

Nociceptors under inflammatory physiological conditions

Answer 10

• Have a LOWER firing threshold

Question 11

Inflammatory pain

Answer 11

• Adaptive response to tissue damage
• TEMPORARY: increased neuron excitability lasts ONLY while inflammatory mediators are present

Question 12

Identify general approaches which can be used to reduce pain hypersensitivity

Answer 12

• Balanced (multimodal) analgesia
  o Targeting pain at different points in it’s transmission to the brain
  >Inhibit peripheral sensation of nociceptors (ex. NSAIDs)
  >Inhibit impulse conduction (ex. local anesthetics)
  >Inhibit central sensitization (ex. alpha-2 agonists)
  >Inhibit perception (ex. opioids)