The Human Brain : From Neurone to Nervous System

MODULATION OF NOCICEPTION IN THE SUPERFICIAL DORSAL HORN


  1. The superficial dorsal horn gives rise to the Spinothalamic tract (from Lamina I in Rexed's classification) and the adjacent Lamina II, the substantia gelatinosa contains interneurones that modulate the strength of the message. This chapter is concerned with the mechanisms involved and their relavance to the control of pain.

  2. Dorsal Horn neurones receive inputs from afferents entering the spinal cord through the dorsal roots; some of these afferents are myelinated (and concerned with touch and proprioception) and others are unmyelinated (and concerned prodominantly with pain and temperature sensation).

  3. These different fibre groups have different destinations within the dorsal horn, where the post-synaptic neurones are arranged in layers. The superficial layers are concerned with transmission of nociceptive signals and their modulation.

    Most of the post-synaptic neurones project to the brain, but others are interneurones that have axons that do not leave the dorsal horn.

  4. Dorsal Horn neurones belonging to the anterolateral system project to thalamus, either directly (the spino-thalamic tract), or indirectly (with synapses on neurones in the reticular formation or the midbrain peri-aqueductal grey matter that also project to the thalamus).

  5. Key Words: Superficial Dorsal Horn; spino-thalamic, spino-reicular and spino-mesencephalic tracts; peri-aqueductal grey matter; nociception; nociceptive transmission.









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