2010 Macbook Pro interferes with Apple TV display

I have a strange problem. My mid-2010 Macbook Pro (with OS X Yosemite 10.10.2) does not have the option for Airplay Mirroring. And yet, if I am watching something on Apple TV (usually Hulu Plus), and at the same time play a video on Macbook, the Apple TV video stops, goes to home page, and sometimes the audio from Macbook is routed to the TV speakers. Is there any way to stop the Macbook from interfering with Apple TV?