Pain receptors were receptive parts of a nervous system responsible for sensing pain and sending the information to the brain. When Ux-Mal criminals took over the bodies of several crewmembers of the USS Enterprise-D in 2368, Commander William T. Riker was spared because he had broken an arm and the firing pain receptors made him immune to the hostile takeover. (TNG: "Power Play" ) Judging by Data's neutralization procedure, Geordi's pain receptors were apparently directly tied into his VISOR implants.