Physiology and Pathophysiology of Pain

Question 1

What is pain?

Answer 1

An unpleasant sensory and emotional input which we primarily associate with tissue damage or describe in terms of damage or both

Question 2

Is pain a stimulus?

Answer 2

Its the final product of complex information processing

Question 3

What is the four step process?

Answer 3

Step 1: Periphery - transmission to spinal cord (first order neurones)

Step 2: Processing - transmission to brain (second order neurones)

Step 3: Brain - Perception, learning and response formation

Step 4: Modulation - descending tracts, inhibition of Substantia gelatinosa

Question 4

Detection of a noxious stimulus by specialised transducers are transmitted via what two types of fibres?

Answer 4

A-delta and C

Question 5

Spinal grey matter is divided into how many rexed areas?

Answer 5

10

Question 6

What is the basis of the ten layer division?

Answer 6

Cytoarchitecture

Question 7

What are the three types of neurone in the grey matter?

Answer 7

Low threshold mechanoreceptive (Layers 3 and 4)

Nociceptive specific (Layers 1 and 2)

Wide dynamic range (Layer 5)

Question 8

Low threshold mechanoreceptors in the spinal cord receive input from what type of fibres?

Answer 8

A-delta

Question 9

Nociceptive specific receptors in the spinal cord receive input from what type of fibres?

Answer 9

C and A-delta

Question 10

WDR neurones in the spinal cord receive input from what type of fibres?

Answer 10

Mainly from A beta but response to both noxious and non-noxious stimuli via interneurones

Question 11

What is the major ascending tract associated with pain sensation?

Answer 11

Spinothalamic tracts

Question 12

What are the two divisions of the spinothalamic tract?

Answer 12

Lateral (neo) and Ventral (paleo)

Question 13

Where does the lateral spinothalamic tract terminate?

Answer 13

Ventroposterior thalamic nuclei

Question 14

What does the lateral spinothalamic tract transmit?

Answer 14

Feeds somatosensory cortex to transmit the spatial, temporal and intensity discrimination of pain

Question 15

Where does the ventral spinothalamic tract transmit?

Answer 15

Projects to cortical regions such as cingulate and insular cortex as well as other parts of the limbic system

Question 16

What is allodynia?

Answer 16

Decreased threshold for nociceptor stimulation (i.e. innocuous stimuli perceived as noxious)

Question 17

What is hyperanalgesia?

Answer 17

Exaggerated response to normal and supernormal stimuli

Question 18

What is spontaneous pain?

Answer 18

Spontaneous activity in nerve fibres perceived as pain

Question 19

What is central sensitisation?

Answer 19

A response of second order neurones in the CNS to normal input to both noxious and non-noxious stimuli typically resulting in pain

Question 20

What are the three main mechanisms of central sensitisation?

Answer 20

Wind-up - progressive increase in the excitability of dorsal horn neurones

Classical - opening of new synapses in the dorsal horn leading to prolonged initial stimuli

Long term potentiation - occurs primarily for very intense stimuli

Question 21

What is neuropathic pain?

Answer 21

Pain initiated by a primary lesion of dysfunction in the tomato-sensory nervous system - almost always chronic