How is REM sleep different from slow sleep?

During slow sleep, breathing and pulse become less frequent, during this period the muscles relax, the motor activity of a person decreases several times. During REM sleep, the respiratory rate, heart rate increase, physical activity increases, sometimes the eyeball can move. It is the movement of the eyeballs that is characteristic of REM sleep. A person needs about four hours to plunge into REM sleep, because first there is a phase of REM sleep.