Central sensitization is the phenomenon in which repetitive constant stimulation of the nociceptive system through C-fibre activity results in progressively increasing responses from the dorsal horn cell, thereby causing progressive increase in pain experience.
N-methyl D Aspartate (NMDA) receptor is believed to be an important factor contributing to this phenomenon.

The term “wind-up” arises from the similarity of a sensitized dorsal horn cell to a “wound-up” spring, which causes exaggerated response to even a gentle stimulus.

Suzuki R, Sikandar S, Dickenson AH. Nociception: basic principles. In: Bruera ED, Portenoy RK (eds) Cancer Pain Assessment and Management. Cambridge University Press. Cambridge, 2010. p. 6.