The Human Brain : From Neurone to Nervous System


  1. The dorsal horn is a layered structure that receives afferent inputs from the skin, viscera and other structures. It is concerned particularly with nociceptive transmission. Signals generated by injurious stimuli to the body are passed to second order neurones, but the strength of the message passed to the brain can be modulated in a number of ways. The second order neurones have axons that pass rostrally in the contralateral antero-lateral white matter, and communicate with the thalamus, per

  2. iaqueductal grey matter and the brainstem reticular formation. 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.

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

  5. 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).

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