Have you ever found yourself drifting off to sleep only to be rudely awakened by your body jerking violently?
You may have felt like you were falling or having a particularly aggressive dream, but it was just your brain causing your body to react to the fact that it moved through the first stage of sleep too quickly.
The hypnic jerk is thought to be caused by a battle between the brain systems concerned with sleep and those that try to help you stay awake:
During this transitional state, the sleeping mechanism usually wins, but the wakeful one sometimes puts up a fight. “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,” he says. And for reasons that are unclear, it’s sometimes accompanied by an image.