I am about to graduate from nursing school, so I hope you don't mind my 2¢ even though this isn't, technically, my forum.
I found that if you knew the A&P - it was MUCH easier to understand the disease process. To me, it was needed more in Cardiac than anything. Understanding the pathway of blood through the heart and what chambers did what, was very important when understanding different complications, CHF, etc. Everything else - a quick review (my prof always did a quick little A&P review at the beginning of each lecture - and I do mean quick - maybe 1 or 2 slides on the PP at most) seemed sufficient. With Cardiac, I actually had to go back and pull out my old A&P book to help me get down to the basics and understand better.
So my answer is it really depends - but it can't hurt to remember as much as possible.