A pain perception organ: A nociceptor is a class of sense organs uniquely excited by noxious stimuli that threaten or produce actual tissue damage.

A nociceptor receptor is stimulated by injury. It is a receptor for pain.

The pain circuit extends from the body's periphery, including the skin and other tissues outside the central nervous system, to the spinal cord and the brain.

In a healthy system, a tissue injury causes pain-sensing nerve cells, or nociceptors, to send a pain-signal message to nerve cells in the dorsal horn of the spinal cord, which in turn pass the message to the brain, which interprets it as pain.

In erythromelagia and other peripheral neuropathies, malfunctions in the nociceptor cells send pain signals even when there is no injury.

Neurons that are multi, or wide dynamic range nociceptors (nerve endings that responds selectively to painful stimuli, causing the sensation of pain): Polymodal nociceptors are activated by heat, mechanical pressure, or chemical mediators of inflammation and are released as a result of tissue injury.