Plasticity of Pain Sensation

Question 1

What is pain hypersensitivity?

Answer 1

a state in which more pain is experienced for a particular injury

Question 2

What are the characteristics of pain hypersensitivity?

Answer 2

• HYPERALGESIA (increased responsiveness to a noxious stimulus)
• ALLODYNIA (pain experienced in response to a normally non-noxious stimulus)

Question 3

What are the two general conditions that pain hypersensitivity occurs under?

Answer 3

1. tissue inflammation (INFLAMMATORY PAIN)
2. damage to the nervous system (PNS or CNS; NEUROPATHIC PAIN)

Question 4

What are the two mechanisms of neural plasticity that underlie inflammatory pain?

Answer 4

1. peripheral sensitization
2. central sensitization

Question 5

What is peripheral sensitization?

Answer 5

increased excitability and increased firing frequency of nociceptors when exposed to inflammatory mediators

Question 6

How does peripheral sensitization occur?

Answer 6

lower threshold for the activation of ion channel receptors in the nociceptor terminal membrane

Question 7

How does the firing threshold of nociceptors change under inflammatory conditions?

Answer 7

• nociceptors have a high firing threshold, under resting physiological conditions
• nociceptors have a LOWER firing threshold, under INFLAMMATORY physiological conditions

Question 8

What is the net result of peripheral sensitization?

Answer 8

• increased firing frequency of nociceptors

Question 9

What is central sensitization?

Answer 9

increased excitability of spinal pain relay neurons, initiated by sustained firing of nociceptors

Question 10

How does central sensitization occur?

Answer 10

increased efficacy of the synapse between the nociceptors and the pain relay neurons

Question 11

What is the net result of central sensitization?

Answer 11

lower firing threshold in pain relay neurons

Question 12

What is another name for central sensitization?

Answer 12

windup pain

Question 13

What is inflammatory pain?

Answer 13

an adaptive response to tissue damage
- time course is temporary (increased neuronal excitability lasts only while inflammatory mediators are present)
- pain hypersensitivity is protective (allows the injured area to be protected until it has healed)

Question 14

what is neuropathic pain?

Answer 14

• pain hypersensitivity due to damage to the nervous system
• A MALADAPTIVE RESPONSE

Question 15

what is the rate of neuropathic pain?

Answer 15

uncommon

Question 16

How does neuropathic pain manifest?

Answer 16

as pain hypersensitivity
- hyperalgesia
- allodynia
- SPONTANEOUS PAIN

Question 17

What is neuropathic pain caused by?

Answer 17

caused by peripheral and central sensitization that is NOT temporary
- increases in neuron excitability & synaptic strength can be long-lasting or become permanent
- called “learned pain”

Question 18

What does balanced (multimodal) analgesia do?

Answer 18

• inhibits transduction (inhibits peripheral sensitization of nociceptors)
• inhibits transmission (inhibits impulse conduction)
• modulation of spinal pathway (inhibits central sensitization)
• inhibits perception

*dont need to know drugs in diagram