calling all experts

I'm still confused. Is a CRNA a specialty designation under the large umbrella of Nurse practitioner? Or, is it a class all by itself? After reading numerous posts about such, I could never come to a definite conclusion! For example, if I were to become a CRNA, could I also decide at some point that I wanted to practice as an NP and so do? Or, would I be required to go back to school and get another graduate degree with an NP specialization?

Question two, is: if the above is affirmative, is this a state-by-state law or is it across the board?

Thanks to all who may acknowledge this!

Espresso Girl