So this is one specific example of a secondary messenger pathway. This is the pathway by which we pass down signals from one cell to a different cell in the body. So in this case we only had one intermediate molecule involved, the neurotransmitter. In this case we had two. We had our epinephrine was the first messenger or the primary messenger and a secondary messenger was our cyclic Amp. So once again, protein kinase A, the enzyme that thus farlates other proteins in the cell can be activated through a secondary messenger system.