This passage is adapted from commonlit staff, “the invisible influence: how our decisions are rarely ever our own.” published 2017 by commonlit .

Second messenger systems: The amino acid-derived hormones epinephrine and norepinephrine bind to beta-adrenergic receptors on the plasma membrane of cells. Hormone binding to receptor activates a G protein, which in turn activates adenylyl cyclase, converting ATP to cAMP.