Pain modulation

Question 1

Types of fibres

Answer 1

C fibres
- unmyelinated
- slow transmission speed
aching pain

A delta

• thinly myelinated
• fast transmission speed
• Fast localised pain

A beta

• thickly myelinated
• very fast transmission speed
• mechanosensation

Question 2

Pain Gate theory

Answer 2

• A beta fibres are stimulated and send an impulse to the inhibitory neuron
• this inhibitory neuron prevents the 1st order neuron (A delta/C fibres from synapsing with the second order neuron
• nociceptive signals are prevented from reaching the brain

Question 3

Descending pain system

Answer 3

1. association areas of the brain stimulate the periaqueductal grey matter
2. PAGM stimulates the Rostro ventral medulla
3. serotonin is released and and descends down the spinal cord
4. Interneurons in the substantia gelatinosa are excited and release opioids
5. Opioids inhibit transmission between 1st and 2nd order neurons

Question 4

Importance of systems in physio

Answer 4

• stimulate A beta fibres to close pain gate e.g. manual therapy
• stimulate A delta fibres to activate descending systems e.g. electrotherapy, acupuncture