Stage Three

Deep, slow brain waves known as Delta Waves begin to emerge during this stage. It is a transitional period between light sleep and a very deep sleep.

Stage Four

This is sometimes referred to as Delta Sleep because of the delta waves that occur during this time. Stage Four is a deep sleep that lasts for about 30 minutes. Sleepwalking and bed-wetting typically happen at the end of Stage Four sleep. (This does not include the problems that can happen with sleep medications like Ambien and Lunesta).

Stage Five: REM

Most dreaming occurs during Stage Five, known as REM. REM sleep is characterized by eye movement, increased respiration rate and increased brain activity. REM sleep is also referred to as paradoxical sleep because, while the brain and other body systems become more active, your muscles become more relaxed, or paralyzed. Dreaming occurs because of increased brain activity, but voluntary muscles become paralyzed. Voluntary muscles are those that you need to move by choice, for example, your arms and legs. Involuntary muscles are those that include your heart and gut. They move on their own.

Rapid eye movement, or REM sleep, is when you typically dream. You may have images float by in earlier stages, particularly when you are going through Alpha or Theta, but the actual dream state occurs in REM.

This period of paralyzation is a built-in protective measure to keep you from harming yourself. When you are paralyzed, you can’t leap out of bed and run. 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.

Cycles

Sleep does not progress through all of these stages in sequence, however. Sleep begins in Stage One and progresses into stages 2, 3, and 4. Then, after Stage Four sleep, Stages Three, then Two are repeated before going into REM sleep. Once REM is over, we usually return to Stage Two sleep. Sleep cycles through these stages approximately 4 or 5 times throughout the night.

We typically enter REM approximately 90 minutes after falling asleep. The first cycle of REM often lasts only a short amount of time, but each cycle becomes longer. This is why we need long periods of sleep each night. If we get short periods of sleep, we can’t really get through the stages we need to heal and stay healthy. REM can last up to an hour as our sleep progresses. In case you are wondering, if you feel like a dream is taking a long period of time, it really is. Contrary to what was once believed, dreams take as long as they actually seem.

Getting sleepy? OK, sleep well, perchance to dream….

Stages of Sleep