1. A molecular structure within a cell or on the surface characterised by selective binding of a specific substance and a specific physiologic effect that accompanies the binding, for example, cell surface receptors for peptide hormones, neurotransmitters, antigens, complement fragments and immunoglobulins and cytoplasmic receptors for steroid hormones.
2. A sensory nerve terminal that responds to stimuli of various kinds. An organ having nerve endings (in the skin or viscera or eye or ear or nose or mouth) that respond to stimulation.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.An organ having nerve endings (in the skin or viscera or eye or ear or nose or mouth) that respond to stimulation.A type of cell or organ that is capable of detecting the presence of a particular stimulus, which in turn, will bring about a response in the organism due to the presence / absence / change in concentration of the stimulus.