Blocking the afferent pathway or stimulating the inhibitory pathway can provide analgesia. These pathways are not hard wired, ie, the importance of each part can change in the short term and neuronal connections can change in the long term. This is sometimes (confusingly) called plasticity.
injury stimulates peripheral Aδ and C fibres
- polymodal nociceptors
•Aδ - sharp localised pain, mechanical stimuli
•C - burning pain, heat or cold
which then project to the CNS:
→ dorsal root
→ substantia gelatinosa of spinal cord
→ spinothalamic / spinoreticular tracts
→ thalamus
→ (cortex) affective rather than sensory?
cortex?
→ thalamus
→ brainstem
→ dorsal horn of cord
Pain pathways and some of the neurotransmitters involved.
Julius & Basbaum, 2001, Molecular mechanisms of nociception, Nature, 413,
203 - 210 A good review of the pathophysiology of pain which is up to date but
still readable.
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copyright
Massey University
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