PHYS Pain Flashcards
Role of substantia gelatinosa
Relays information re. pain, temp. & mechanical info.
Substantia gelatinosa lamina no.
I&II
Nucleus propius lamina no.
IV-VI
Where do A-beta fibres synapse in the spinal cord?
Laminae III, IV, V
Role of nucleus propius
Relays info. re. mechanical & temp. sensation.
Where do A-delta fibres synapse in the spinal cord?
Laminae I, II, V
Where do C fibres synapse in the spinal cord?
I, I-V (second order)
Gate Control Theory
• If the gate is open, pain signals can pass through and will be sent to the brain to perceive the pain.
• If the gate is closed , pain signals will be restricted from travelling up to the brain, and the sensation of pain won’t be perceived.
If someone experiences a painful (noxious) stimulus, the application of a non-noxious (soothing or light rubbing) stimulus can help activate the gate control mechanism and reduce the pain.
How is the ‘gate’ closed?
A-beta fibres form excitatory connection w inhibitory neuron.
What contributes to central sensitisation?
Increased NMDA receptor activity of dorsal horn & microglial activation (post nerve damage) -> excitation of neurons (incl. inhibitory neurons).
What can block increased NMDA receptor activation?
Ketamine.
Convergence-projection theory.
.Referred pain may be due to visceral afferent nerves converging on 2nd order neurons of the somatic sensory pathway -> dorsal horn neuron hypersensitivity (where hyperreactivity is interpreted as coming from the cutaneous site).
