Physiology and Pathophysiology of Pain

Question 1

What is pain?

Answer 1

An unpleasant sensory and emotional experience which we primarily associate with tissue damage

Question 2

What is step 1 in the pain pathway?

Answer 2

Detection in the periphery: transmission to the spinal cord by 1st order neurons

Question 3

What is step 2 in the pain pathway?

Answer 3

Processing in the spinal cord: transmission to the thalamus by 2nd order neurons

Question 4

What is step 3 in the pain pathway?

Answer 4

Perception, learning and response

Question 5

What is step 4 in the pain pathway?

Answer 5

Modulation: descending tracts

Question 6

What is nociception?

Answer 6

The detection of tissue damage by specialized transducers connected to A-delta and C fibers

Question 7

Which stimuli do nociceptors responds to?

Answer 7

Thermal, chemical, mechanical and noxious stimuli

Question 8

Where do 1st order neurons synapse and where do they have their cell bodies?

Answer 8

Cell body in dorsal root ganglion

Synapse at spinal cord

Question 9

What fibres do the lateral spinothalamic tracts carry?

Answer 9

Fast and slow pain

Question 10

What fibres do the anterior spinothalamic tracts carry?

Answer 10

Simple touch sensation

Question 11

Where does the spinothalamic tract arise?

Answer 11

Rexed lamina 2 & 5

Question 12

What is the function of the thalamus?

Answer 12

Secondary relay station

Question 13

Where does pain perception occur?

Answer 13

Somatosensory cortex

Question 14

What is hyperalgesia?

Answer 14

Increased perception of pain or perception of non-noxious stimuli as noxious stimuli

Question 15

What is allodynia?

Answer 15

hyperalgesia to light touch

Question 16

What changes to the nociceptor are seen in allodynia?

Answer 16

Decreased threshold for response

Question 17

What changes to the nociceptor are seen in hyperalgesia?

Answer 17

Exaggerated response to normal and supranormal stimuli

Question 18

What changes to the nociceptor are seen in spontaneous pain?

Answer 18

Spontaneous activity in nerve fibres

Question 19

What are the characteristics of acute pain?

Answer 19

<1 month, obvious tissue damage, increases nervous system activity, pain resolves upon healing and is protective

Question 20

What are the characteristics of chronic pain?

Answer 20

Pain for more than 3 months, beyond the expected healing period, with no protective function and which degrades health and function

Question 21

What is nociceptive pain?

Answer 21

A sensory experience that occurs when specific peripheral sensory neurones respond to noxious stimuli

Question 22

What are the characteristics of nociceptive pain?

Answer 22

Painful region is localised to site of injury, usually time limited/resolves when damaged tissue heals (can be chronic) and tends to respond to conventional analgesics

Question 23

What is neuropathic pain?

Answer 23

Pain initiated or caused by a primary lesion or dysfunction in the somato-sensory nervous system

Question 24

What are the characteristics of neuropathic pain?

Answer 24

Painful region may not be the site of injury, almost always chronic and responds poorly to conventional analgesics

Question 25

Which therapies affect the transduction of pain?

Answer 25

NSAIDS, ice, rest and LA blocks

Question 26

Which therapies affect the transmission of pain?

Answer 26

Nerve blocks, drugs (opioids and anticonvulsants) and surgery (DREZ and cordotomy)

Question 27

Which therapies affect the perception of pain?

Answer 27

Education, cognitive behavioural therapy, distraction, relaxation, graded motor imagery and mirror box therapy

Question 28

Which therapies affect the descending modulation of pain?

Answer 28

Placebos, drugs (opioids and antidepressants) and surgery (spinal cord stimulation)