You know that feeling when you're almost asleep, but suddenly wake up to a shock in your body? Like falling down a small abyss.
Such a shock or falling sensation between being awake and sleeping is called a hypnagogic shock or sleep fit. The exact cause is not clear to scientists. The most common theory is that our brains switch from a conscious – awake – to an unconscious – sleeping – state. This changing of the guard seems to be the cause of the shock:the part of your brain that controls your perception is already asleep, but your muscles are not that far yet.
