You learn many medical things, as well as nursing theory--like disease path, symptoms, standard and even experimental treatments, expected and unexpected responses to treatments, pharmacology, associated side effects/problems with treatments--pharmacological or otherwise, planning of care and evaluation--assessment, diagnoses (medical awareness for the actual medical diagnoses) but can document on your assessment findings only what is stated by patient or physician, etc and then only nursing diagnoses--which are basically how the diagnoses present in a general way. You learn complications of diseases and treatments and preventative measures, risk factors, current research and stats, etc. Thing is, you don't go into a deeper understanding of the disease processes or necessarily (it depends on the nurse and area of work--such as critical care compared to say med surg) the modality of actions of treatment on the cellular level, in general, as compared with medicine. Now this can change as per the individual nurse and the area in which she/he works and his/her own dedication to study while in direct practice. You also have to have a greater depth of understanding to score high on the CCRN, which is specialization in critical care, after NCLEX and working in critical care for I think at least 2000 hours. The hours requirement may have changed since I took it..
After all this and other things, you have to learn a lot of nursing theory and application, which, in my mind is far from "all bad," meaning there is a lot of good in learning the theories and approaches to application; b/c in general, much of it is very holistic.
But for the sciences, like anything, it will depend upon the individual. E.g., I was fascinated to learn about drug mechanisms of actions against microbial cells in microbiology. Not every student or nurse will be that interested, and well, that is that individual's loss IMHO.