Can I include in my academic CV that I have attended and completed the Coursera and Udacity classes I have been taking? I understand that these are not anything major, but the courses definitely gives a good overview and starting formal study on the subject becomes less cryptic. If I can include them without any negative impacts, then under what section should I include them?
Yes. The certified courses that connect to skills that doesn't directly apply to your mainstream degree deserves to be in your academic CV. It will show, to an extent, an interdisciplinary qualification that you possess. There are many real life instances where this has helped a lot, especially in industrial placements, career change, and interdisciplinary research.
There are some courses from MOOC you ought not to add in your CV. These include those that overlaps the courses you've already completed as per your educational degrees, minor introductory courses, and those that wouldn't prove a significant impact in your career point of view.