Nociception: pain pathways and descending modulation
The IASP definition and categories of pain, nociceptor transduction channels and the inflammatory mediators that sensitise them, A-delta and C fibre conduction, dorsal horn processing and gate control, the spinothalamic pathways, referred pain, and descending modulation from the periaqueductal grey and locus coeruleus, with the drug and lesion questions they generate.
Tier 1Medical sciences concept
Written with AI assistance and fact-checked against the sources below. For exam study, not clinical decisions. How notes are made
At a glance
- The IASP (2020) defines pain as an unpleasant sensory and emotional experience associated with, or resembling that associated with, actual or potential tissue damage. Nociception is the neural process of encoding noxious stimuli; the two can come apart.
- Pain is grouped as nociceptive, neuropathic or nociplastic (since 2017). Mixed pain is common, particularly in cancer.
- The pathway has four steps: transduction at the nociceptor, transmission along A-delta and C fibres, modulation in the dorsal horn and perception in the thalamus and cortex.
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Sources
- Raja SN et al. The revised International Association for the Study of Pain definition of pain: concepts, challenges, and compromises. Pain 2020;161:1976-82International Association for the Study of Pain, 2020
- Principles of Neural Science (6th ed.)McGraw Hill (Kandel, Koester, Mack and Siegelbaum, 2021), 2021
- Melzack R, Wall PD. Pain mechanisms: a new theory. Science 1965;150:971-9Science, 1965
- Cox JJ et al. An SCN9A channelopathy causes congenital inability to experience pain. Nature 2006;444:894-8Nature, 2006
- Keam SJ. Suzetrigine: first approval. Drugs 2025;85:845-51Drugs, 2025
- Last updated
- 14 November 2026
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