Picture the scene. You're having your usual dream, you know the one, where you're talking and all of a sudden your teeth fall out.

(Teeth falling out is one of the most common dreams in the UK, apparently it means you regret something you've said or you're afraid some something in your life changing.) With your teeth all over the floor and you all vulnerable, your body jolts. BLAM. If you're sleeping next to someone who sees, they're left rather confused. What just happened? Did you have a "kick" like in Inception?

(Warner Bros. Pictures via GIPHY)

The proper term for you jerking in your sleep (no, not that kind), is a hypnic jerk. During the first few stages of you falling asleep, your body likes to slow everything right down. Your heart rate and breathing slow down and your brain gets itself ready to chill out. But sometimes, if you are really exhausted, your body can go through these slow-down processes too quickly. You heart rate and breathing slow down too quickly and your brain thinks you may be dying. Cue the hypnic jerk. The hypnic jerk is your brain's quick "YO! ARE YOU OK?" message to the rest of the body. You jerk in your sleep because your brain wants to make sure you are still alive. How cool is that? Thanks for looking after us brain. Now let us get the fuck back to sleep, we got work in the morning.