A Physician Assistant requires a minimum Bachelor of Science degree. I understand this may change soon. They work under the supervision of a physician, and that physician is fully responsible for the actions of the PA.
A Nurse Practitioner in most states requires or will soon require a Master of Science Degree and additional education in the area of Advance Practice (Family, Adult, Pediatric, etc.). The NP works independently, and in most states needs a collaborative agreement with a physician. The NP works under his/her RN license.
Both the PA and the NP have similar scopes in terms of gathering health history, history of present illness, differential diagnosis, treatment and evaluation.
My experience is that the PA is more medical model focused, and the NP is more a combination of medical model and nursing model focused.
My ex is a PA and I am in an advance practice nursing program
, our care delivery styles are like night and day. But, we still consult eachother with questions and advice when we need another point of view.