At my school,
as a pre-req for Anatomy, Physiology and Micro, you needed a lab science so I took my Chem class. To even be considered for admission to the nursing program, you had to have chem out of the way. I took chem first. Then (can you say crazy) I took both Anatomy and Microbiology along with English 100 while I was working fulltime. Anyway, got through that semester and then took my Physiology the next semester. My words to you are to get as many courses out of the way as possible before you get into your nursing program. Once you are in, you will have no time for anything else.
Hope this helps a little.