Pain

Question 1

What is the descending pathway responsible for?

Answer 1

It controls and inhibits the ascending pathway

Question 2

Describe the descending pathway

Answer 2

1. 1st order neuron brings action potential to stimulate vesicles (using substance P) to release contents into synaptic cleft. Substance P also stimulates 2nd order neuron
2. In the thalamus - 2nd order neuron synapses with 3rdON. 3rd then relays impulse to region of brain where pain is felt
3. Specific neurons release NA and serotonin
4. NA and serotonin cause:
   - inhibition of substance P
   - stimulation of interneurons in substantia gelatinusa to release enkephalin
5. Enkephalin:
   - inhibits substance P
   - inhibits depolarisation of postsynaptic neuron

Question 3

What does the cortex do?

Answer 3

• Region of the brain that perceives pain
• 3rd order neuron let’s cortex know where the injury is

Question 4

Explain the who pain ladder

Answer 4

• world health organisations guide on how to treat nociceptive pain
  1. Start with weak analgesics and tritrate to max dose if needed (paracetamol or ibuprofen). Try para + NSAID before step 2
  2. Add weak opioid eg codeine/tramadol and titrate to max dose if needed
  3. Try strong opioid eg morphine/oxycodone

risk of opioid overdose - respiratory depression, heavy sedation, constricted pupils

Question 5

Give examples of mu receptor agonists

Answer 5

WEAK
• codeine/dihydrocodeine

MODERATE
• oxycodone
• fentanyl
• alfentanil

STRONG
• morphine/diamorphine