WordNet (r) 3.0 (2006):

receptor
    n 1: a cellular structure that is postulated to exist in order
         to mediate between a chemical agent that acts on nervous
         tissue and the physiological response
    2: an organ having nerve endings (in the skin or viscera or eye
       or ear or nose or mouth) that respond to stimulation [syn:
       sense organ, sensory receptor, receptor] [ant:
       effector]