What happens to your body during a panic attack?

Popular Science 

What happens to your body during a panic attack? 'Just breathe' is more than just a nice saying. Up to one third of people experience at least one panic attack in their lifetimes. Breakthroughs, discoveries, and DIY tips sent every weekday. It happens all at once--your heartbeat becomes a jackhammer, your body closes in on you like a corset.