Hi Erin,
 
I hope you are doing well! While physiology is not directly a pre-med requirement, it is definitely helpful to take a physiology course before the MCAT as the B/B section will cover physiology topics. PHYSIOL 201 and PHYSIOL 502 are actually both introductory physiology classes, meaning no physiology knowledge is required before taking these courses. However, PHYSIOL 502 is just a more advanced and fast-paced introductory physiology course and it is also taken by graduate students. Additionally, since PHYSIOL 502 is a 300+ level course, it can also be used as an upper-level biology course for medical school application purposes. So, taking either one of these courses should prepare you well for the MCAT.
 
There are differences in the prerequisites for the two courses, where PHYSIOL 201 just requires sophomore standing and prior chemistry exposure, while PHYSIOL 502 has an advisory prerequisite of a college-level biology course and biochemistry course. The grade distribution and workload (found on Atlas) appear to be pretty similar between these two courses, where both courses have a median grade of a B+ with about ~50% of students getting an A- or above, but 55% of students perceived the workload of PHYSIOL 201 as being heavier than other courses while 49% perceived PHYSIOL 502 as having a heavier workload. Additionally, PHYSIOL 201 is traditionally composed of sophomores, juniors, and seniors while PHYSIOL 502 is almost exclusively taken by graduate students and seniors.
 
I hope this information helps choosing between these two courses a little bit easier! Feel free to stop by our advising hours (on Sunday – Wednesday from 6 – 10 PM) if you have any further questions!
 
Best,
Raheem, PMH Co-President