You know that moment when you're totally relaxed, drifting into a blissful sleep, and suddenly, you jerk awake because you dreamed you were falling... or something?
Yeah, there's a name for that. It's known as a "hypnic jerk" or "sleep start."
Experts have yet to determine exactly why it happens, but Dr. Carl Bazil, director of the Columbia Sleep Disorders Center told New York magazine it probably has something to do with your brain sending itself mixed signals.
Basically, there's a fight between two brain systems -- the one that wants you to fall asleep and the one that wants to keep you awake.
Dr. Bazil told New York magazine,
One of the things that happens as you fall asleep is your muscles relax, but the awake part may still be stimulating enough that it will temporarily overreact and you get this jerk of muscle activity. It doesn't usually mean anything, so there hasn't been a huge amount of resources devoted to figuring it out.
Although not everyone is subject to hypnic jerks, about 70 percent of people experience them, even if they don't remember.
So the next time your boyfriend or girlfriend suddenly jerks and wakes you up, cut him or her some slack. You're probably doing it, too.