physiology of pain

Question 1

nociceptive pathway

1. periphery

Answer 1

tissue injury
release of chemicals
stimulation of pain receptors
alpha / c fibres

Question 2

nociceptive pathway

2. spinal cord

Answer 2

first relay station
a delta and c fibres transfer over
second order nerve travels up opposite side of the spinal cord to the brain

Question 3

nociceptive pathway

3. brain

Answer 3

info to the thalamus - second relay station

connection to many parts of the brain- cortex (motor and sensory) limbic system (emotional effect of pain), brainstem (autonomic reflex) and frontal lobes (works out how this pain relates to me in the world)

pain perception occurs n the brain

Question 4

nociceptive pathway

4. modulation

Answer 4

descending pathway from the brain to the dorsal horn
usually inhibits pain signals from the periphery

the brain can potently inhibit and switch off pain signals itself (battle field injury)

Question 5

placebo treatment

Answer 5

psychological factors

Question 6

neuropathic pain

Answer 6

pathological pain
not from the nociceptive pathway
this is DAMAGED nervous system

peripheral nerves
spinal cord
brain (stroke)

needs different pharmacological treatments

Question 7

mechanism of neuropathic pain

Answer 7

aboral nerve tissue grows after amputation e.g. amutpative neuroma

abnormal firing of nerves

changes in the chemical signalling in the dorsal horn (shingles, virus damages and changes the chemical signalling)

abnormal nerve connections in the dorsal horn

loss of normal inhibitory functioning (trigeminal neuralgia)

Question 8

other meds that use synertinergic etc

Answer 8

tramadol
tarpentdol
TCA
anticonvulsants
ketamine
local anaesthetic

useful for breakthrough neuropathic pain

Question 9

opioid and addiction

Answer 9

addiction is very rare in acute pain and cancer pain. more likely in chronic non cancerous pain

Question 10

RAT approach

Answer 10

recognise

assess (severity, type, other factors)

• ask the patient
• at rest/movement
• how does it affect life- move, cough, work

treat (non drug tx, drug tx)