receptors Definition

receiver: such as

a cell or group of cells that receives stimuli : sense organ

a chemical group or molecule (such as a protein) on the cell surface or in the cell interior that has an affinity for a specific chemical group, molecule, or virus

any of a group of receptors that are present on cell surfaces of some effector organs and tissues innervated by the sympathetic nervous system and that mediate certain physiological responses (such as vasoconstriction, relaxation of intestinal muscle, and contraction of most smooth muscle) when bound by specific adrenergic agents

any of a group of receptors that are present on cell surfaces of some effector organs and tissues innervated by the sympathetic nervous system and that mediate certain physiological responses (such as vasodilation, relaxation of bronchial and uterine smooth muscle, and increased heart rate) when bound by specific adrenergic agents

muscle spindle