So these secondary messengers are intracellular agents, they could be molecules or ions whose concentration can be greatly amplified, thereby amplifying the overall signal that was initially taken up by that cell. So these secondary messengers typically act on proteins or enzymes that play crucial roles in the signal transduction pathways. And so in our discussion, these are the secondary messengers that we discussed, except in this particular case, we actually didn't discuss how calcium or cyclic Amp is used by this pathway. So let's begin with Epinephrine signaling. So in Epinephrine signaling, we said that once a specific protein, the G alpha protein, binds until adenolate cyclists. It stimulates Adenon cyclists to transform ATP into C amp.