Pain is transmitted along a three-neuron pathway that relays pain signals from the periphery to the cerebral cortex. First order neurons are located in the dorsal root ganglia. Each neuron has a single short axon that bifurcates, sending one end to the peripheral tissues it innervates and the other end to the dorsal horn of the spinal cord where it synapses with the second order neuron. Pain fibers may ascend several segments in Lissauer’s tract before synapsing with second order neurons in the grey matter of ipsilateral dorsal horn. Third order neurons are located in the thalamus and send fibers to somatosensory areas I and II in the post-central gyrus of the parietal cortex as well as the superior wall of the sylvian fissure.
KeywordsNeuroanatomy Pain pathways Nociception Order neurons Pain transmission
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