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Pain pathways - Coggle Diagram
Pain pathways
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Pain Pathways
Tissue damage releases chemical mediators e.g. Bradykinin, 5HT & protons which depolarise the C fibres
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Activation of the neurones results in release of neuropeptides (Substance P) & glutamate from their terminal endings in the dorsal horn of the spinal cord
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The fibres synapse with the ascending projection fibres which run from DH to the Thalamus called the Spinothalamic tract.
Endogenous Opioids
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4) Inhibiting neuropeptide & glutamate release from peripheral sensory nerves synapsing with Dorsal Horn Neurones
Peripheral Pathway
This synapse in the Dorsal Horn is the 1st major regulatory junction in the pain pathway = Gate of Pain Pathway.
There are small inhibitory interneurones in the Dorsal Horn, which inhibit the transmission across the 1st synapse of the pain pathway.
These are rich in natural opioid peptides (enkephalins) and opioid receptors and are the site of action of opioid analgesics.
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Gate Control Theory
Pain transmission in the Dorsal Horn Neurone is regulated by a gating mechanism which consists of inhibitory input from GABAergic and enkephalinergic (enkephalin) Interneurones in the spinal cord.
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Central Pathway
The Spinothalamic tract ascends in the spinal cord and projects the pain signals to the contralateral Thalamus
From the thalamus, pain signals pass to cortex and other CNS centres to elicit the conscious sensation of pain and the emotional response