I agree with the above posts.
I did the same thing actually and was very dissappointed with my senior year as well. It was, well, pissy.
But, you are now stronger in a way, because you will be trying much harder to succeed in your future. This will hopefully result in an upward trend, which med schools love.
Do well in the upper level science class and you will be fine. Oh, and don't forget the wonderful MCAT. Good luck!