It happens all at once—your heartbeat becomes a jackhammer, your body closes in on you like a corset. The dizziness, shortness of breath, and catastrophic thoughts are so formidable, you think you might be dying, even though you're in perfect health.

Up to one third of people experience at least one panic attack in their lifetimes. At its core, a panic attack is an overreaction of the body's normal response to perceived danger. Sometimes the cause is obvious—like a real threat or a big change—but other times, it seems to appear out of the blue.

"This is our fight-flight-freeze response," clinical psychologist Dr. Reid Wilson, author of Don't Panic: Taking Control of Anxiety Attacks, tells Popular Science. "Your body and mind are trying to protect you as a reaction to [a] perceived threat." 

What happens in your body when you panic

When we perceive an external threat through our five senses, the senses' ambassador in the brain—the thalamus—fires off a message. This message is sent deep inside the brain to the amygdala, a tiny bundle of nerves that serves as our chief arbiter of curiosity and avoidance.  The amygdala interprets that message and sends a distress signal to the hypothalamus, the command center for involuntary bodily functions, like breathing. The hypothalamus then sends a chemical S.O.S. to the adrenals, prompting them to dump cortisol and adrenaline into the bloodstream.