The Stages of Sleep

When we go to sleep at night, our bodies are very busy. We go through several stages of sleep before we wake up in the morning. The following are the stages of the sleep cycle in detail, courtesy of the American Academy of Family Physicians:

Stage one:
In this stage, your brain gives the signal to your muscles to relax. It also tells your heart to beat a little slower, and your body temperature drops a bit.

Stage two:
After a little while, you enter stage two, which is a light sleep. You can still be woken up easily during this stage. For example, if you hear a car horn outside you'll probably wake up.

Stage three:
When you're in this stage, you're in a deeper sleep, also called slow-wave sleep. Your brain sends a message to your blood pressure to get lower. Your body isn't sensitive to the temperature of the air around you, which means that you won't notice if it's a little hot or cold in your room. It's much harder to be awakened when you're in this stage, but some people may sleepwalk or talk in their sleep at this point.

Stage four:
This is the deepest sleep and is also considered slow-wave sleep. It's very hard to wake up from this stage of sleep, and if you do wake up, you're sure to be out of it and confused for at least a few minutes. Like they do in stage 3, some people may sleepwalk or talk in their sleep when going from stage four to a lighter stage of sleep.

Stage five - REM stage:
This stands for Rapid Eye Movement. Even though the muscles in the rest of your body are totally relaxed, your eyes move back and forth very quickly beneath your eyelids. The REM stage is when your heart beats faster and your breathing is less regular. This is also the stage when people dream.

While you're asleep, you repeat stages two, three, four, and REM about every 90 minutes until you wake up in the morning. For most, that's about four or five times a night.