E or NE bind either α1, α2 or β-adrenergic receptors. α1 couples to Gq, which results in increased intracellular Ca2+ which results in smooth muscle contraction. α2, on the other hand, couples to Gi, which causes a decrease of cAMP activity, resulting in smooth muscle contraction. β receptors couple to Gs, and increases intracellular cAMP activity, resulting in e.g. heart muscle contraction, smooth muscle relaxation and glycogenolysis.
β1 (eg metoprolol is a β1 blocker) & β2 (eg albuterol is a β2 agonist) receptors work by Gs (AC -> cAMP -> PKA), while α1 (eg terazosin is an α1 blocker) work by Gq (PLC -> PIP2, IP3 -> Ca2+, DAG -> PKC. Besides the heart, β1 receptors are used for aqueous humor production.