• Transmission of impulses, which as they reach consciousness will be interpreted as pain, begins with the activation of specific peripheral receptors called nociceptors by disease- or surgery-induced tissue injury.

• Nociceptors usually respond to high intensity, potentially damaging stimuli.

  • Inflammatory processes often associated with disease or tissue trauma play a role in the initiation of nociception, mostly by sensitizing the nociceptors:

    • which causes lowering of their activation threshold.

  • Both A- and C-class nociceptors and their corresponding afferent fibers are the most important carriers of nociceptive stimuli from the skin, deep somatic structures, such as muscle and bone, and viscera.

  • On going nociceptor-evoked discharges carried by these afferent fibers enter the spinal cord via the dorsal roots, extending into several ascending nociceptive pathways.

  • The dorsal horn is not only a relay station for these signals, but also an area in which complex data integration of excitatory or inhibitory modulation occurs.

courtesy of Roxane Pain Institute used with permission http://www.roxane.com