epinephrine

[KTK]

How does each of the components of the pathway return to its inactive state when epinephrine is removed?

[telomerase]

generally speaking, signals recieved from outside the cell has to be tranduced across the cell membrane through the cytoplasm and into the nucleus where they cause changes in transcriptional activities.

a simple model for signal transduction would look like this:

ligand ---> receptor ---> cytoplasmic signal transmitters ---> nuclear transcription factors ---> change in cellular activity

in your case, you should be looking at the cytoplasmic tyrosine kinases such as Raf, MAP kinase and MEK.

each of these should be phosphorylated to get into their active forms... dephosphorylation leads to inactivation... dephosphorylation is normally catalysed by phosphotases.