What happens during the REM sleep stage?
During REM sleep, you dream actively, but your limb muscles are immobile. Your breathing is rapid, irregular, and shallow. Your heart rate increases, your blood pressure rises, males may have penile erections, and females may have clitoral enlargement. Your brain is at least as active during REM sleep as it is when you are awake. Because your major muscles do not move during REM sleep, you will not act out your dreams. (Sleepwalking occurs during NREM sleep.) Infants spend about 50 per cent of their sleep time in REM sleep; after infancy, you spend fifteen to twenty per cent of your sleep time in REM sleep.
