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Imagine that you're relaxed and drifting off to sleep when suddenly an arm or leg twitches and you have the sensation of falling out of bed. If this has happened to you, you've experienced what sleep specialists call a hypnic jerk or sleep start. Sleep starts happen in normal, healthy people and don't ordinarily require any medical treatment. However, certain medical conditions can make you jump in your sleep and should be evaluated by your physician.
REM sleep is sometimes referred to as paradoxical sleep by scientists because it is a period of sleep characterized by rapid periodic twitching movements of the eye muscles and other physiological changes, such as increased breathing and heart rate, increased brain activity, and muscle relaxation.asically: you look asleep, but your brain is wide awake. REM sleep is when we remember our dreams, so it makes sense that our brains are most active when we are dreaming, seeing as that dreams require a lot of mental activity. 14 people found this useful.