6 Bizarre Things Your Brain Does While You Sleep

You Feel Like You're Falling — And You Jerk Awake

You’re drifting off, perfectly comfortable, when suddenly you feel like you’re plummeting off a cliff. You jerk awake, heart pounding. This is a hypnic jerk — a sudden, involuntary muscle contraction that strikes as you’re falling asleep. Scientists believe it’s caused by a conflict in your brain as it shuts down for sleep. As your muscles relax, your brain misinterprets it as actual falling and jolts you awake to “save” you. It’s completely harmless — just your brain being a bit paranoid about gravity.