Can I include the completion of Udacity and Coursera classes I have attended in an academic CV? 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?
No.  Specific coursework (whether formal or informal, online or in-person) does not belong in an academic CV.