APA Dictionary of Psychology

a receptor that binds norepinephrine. There are two main types, designated β₁ and β₂. The former mediate stimulation of heart muscle, causing a faster and stronger heartbeat. The latter are associated with relaxation of smooth muscle, causing (for example) dilation of blood vessels and widening of airways. Also called beta adrenoceptor; beta adrenoreceptor; beta receptor. Compare alpha-adrenergic receptor.