Is it appropriate to list completion of online courses (eg. Coursera) on your academic CV?
In your case, yes. Since your mainstream subjects connected to medicine differ widely from what you intend to showcase, i.e., data science and analytics, it would be advisable to add such subjects to your academic CV. Fields like genomics and bioinformatics look for candidates having skill sets in both medicine and data science. But this is applicable provided that you are certified in those subjects. It wouldn't be much of use otherwise.
There are some MOOCs people might attend out of interest, and even get certified, but does not create an impact in the CV, such courses are to be avoided in an academic CV to prevent losing focus of the actual achievements that connect to their objective.
Where would you put it in context of your other CV sub-headings?
This is a matter of preference as CVs can vary widely depending on people, culture and the jobs you target. I would put it under a section named Auxiliary Certifications section. I did find this practice indeed useful in my career.