Figure 2.

Diagram illustrating how peripheral and central sensitization can lead to pain. (A) Condition with no pain. Normal nociceptor activity and central neuron activity usually do not produce pain. (B) Condition with peripheral sensitization. Enhanced nociceptor activity activates nonsensitized central nociceptive neurons to result in pain. (C) Condition with central sensitization but without peripheral sensitization. Normal activation of nociceptors activates sensitized central neurons to result in pain. (D) Condition with both peripheral sensitization and central sensitization contributing to pain. Treatments aimed at peripheral nociceptive input would be effective in people with peripheral sensitization but would have minimal effects in people with central sensitization and partial effects in people with both peripheral sensitization and central sensitization.