
Originally Posted by
bulldawg_28
I got that out of my A&P book. Here's the paragraph.
Adrenergic Receptors
There are also two major classes of adrenergic (NE binding) receptors:alpha and beta. Organs that respond to NE have one or both types of receptor. In general, NE bind to a receptors is stimulatory, and their binding to B receptors is inhibitory. But there are exceptions. For example, binding NE to the B receptors of cardiac muscle prods the heart into more vigorous activity. These differences reflect the fact that both a and b receptors have two or three receptor sublcasses (a1, and a2; b1, b2, and b3) and each receptor type predominates in certain organs. (Human Anatomy & Physiology Sixth Edition; Elaine N. Marieb)