How are beta receptors?

Affinity (strong response to isoproterenol less sensitive to NE and EPI iso>epi>NE three subgroups b1, b2 and b3 based on affinity and response) Responses (b1 equal affinity to NE and Epi, b2 higher for epi seen in skeletal muscle vasculatures respond to hormonal effects of circulating EPI by adrenal medulla) Second messengers (activate adenylyl cyclase increases cAMP