The eyes are closed during Stage 1 sleep, and you can be awakened without difficulty; however, if aroused from this stage of sleep, you may feel as if you haven’t slept. Stage 1 may last for five to 10 minutes. During this time, you may feel like you’re falling, which may cause you to jump suddenly (called hypnic myoclonic).
During this light period of sleep the heart rate slows and the body temperature decreases. At this point, the body prepares to enter deep sleep.
Stages 3 and 4:
These are deep sleep stages, with Stage 4 being more intense than Stage 3. This is when REM sleep occurs. These stages are known as slow-wave, or delta, sleep. If aroused from sleep during these stages, a person may feel disoriented for a few minutes.
Most dreaming occurs during Stage 5, known as REM. REM sleep is characterized by eye movement, increased respiration rate and increased brain activity. Your brain and other body systems become more active while your muscles become more relaxed. REM sleep is when you typically dream because of increased brain activity. Voluntary muscles become paralyzed, and this period of paralysis is a built-in protective measure to keep you from harming yourself. Do you ever feel like you can’t escape during a dream? Well, the truth is, you can’t. You can breathe, and your heart is working, but you really can’t move.