Norepinephrine uses the Second Messenger System, which means, cells signal to each other what molecules have been released that will trigger a physiological reaction.
This phenomenon is activated after the ligand (ion or molecule) is bonded to its receptor
(protein molecule), creating a variation that causes a chain-reaction, that will
finally activate the Second Messenger. The latter will activate intercellular
molecules that will be able to control the cell’s activity.
