It depends upon a lot of factors. Do you have to work while you go to school? Do you have kids? Does your school count GPA for acceptance into the nursing program?
If the nursing school
counts GPA, you have to figure what happens if the course load is too much and it adversely affects your GPA and, therefore, chances of acceptance. Also, if you decide to take a W late in the semester because the course load is too much, does the school count W's against you?
My school doesn't allow you to take all three together because Anatomy is a pre-req for Physio. But, from what I understand, 80 percent of the people who take Anatomy and Micro together fail at least one of the courses. And 90 percent of the people who take Physio and Micro together fail at least one of courses. (By failing I'm also talking about D's since anything less than a C is not accepted.) Basic Bio and Chemistry are pre-reqs for all three courses.
However, many of those people work and also have kids. Those stats probably aren't nearly as high for students who don't have to work and don't have kids. I managed to pull A's in Anatomy and Micro in one semester, but I basically did nothing but study.
Just some food for thought. BTW, I wouldn't sweat the labs too much. If you do well with the lecture material, you'll probably do well with the labs. While labs aren't always directly related to lecture, most of it is.