All human beings require sleep. Sleep helps to restore the mind and body so they can continue to function properly. Sleep also helps the body’s ability to heal itself. Doctors and chiropractors study sleep in order to help their patients with care and pain management. Understanding how sleep works help us understand just how important it is to our physical and mental health. Let’s examine the five stages of sleep to get a better understanding.
What are the five stages of sleep?
Sleep studies have helped determine how the five stages of sleep work. Each stage is a different level of sleep. These five stages are placed in two separate categories: Non-REM and REM. Non REM sleep consists of the first four stages of sleep: Stage I, Stage II, Stage III and Stage IV. Stages III and IV are referred to as deep sleep or delta sleep. REM sleep is a stage all its own. It’s the deepest form of sleep possible. Many sleep experts describe it as that of an active brain inside of a paralyzed body. This is the stage that humans hope to get to in order to get a good night sleep.
Non-REM, or NREM, is short for Non-Rapid Eye Movement. It’s also referred to as quiet sleep. While you’re in the earliest sleep stages, in a way, you’re still alert and awake. That’s why it’s so easy to be awakened by sounds such as someone calling your name when your first fall asleep.
Stage I Sleep
This is the very beginning of the cycle of sleep. During Stage I, you’re sleeping relatively light. It’s considered to be a period of transition between being awake and being sleep. It usually lasts only about 5-10 minutes. This is that stage of sleep where you hear people say “I wasn’t asleep.”
Stage II Sleep
During the second sleep stage, your brain starts producing bursts of rhythmic, rapid brain waves. These wave bursts are called sleep spindles. Your body temperature also begins to decrease, while your heart rate slows down. Stage II sleep lasts for about 20 minutes.
Stage III Sleep
During the third stage of sleep, slow brain saves begin emerging. These are called delta waves. Stage III sleep is a period of transition between being in a light sleep and going into an extremely deep sleep.
Stage IV Sleep
Stage IV sleep is also called delta sleep because of the constant delta waves occurring during this time. This stage provides a deep sleep. Bed-wetters and sleep-walkers tend to have their “accidents” at the end of this stage. The fourth stage of sleep lasts for about 30 minutes.
REM is short for Rapid Eye Movement. REM sleep is also called paradoxical sleep or active sleep. This is Stage V Sleep. During the fifth and final stage, eye movement increases to a rapid rate. Brain activity and heart respiration rates also increase. It’s also called paradoxical sleep because, during REM sleep, the brain and other systems in the body become more active, but your body’s muscles are more relaxed. Although the body is now in a paralyzed state, the increased brain activity causes you to have dreams during the fifth stage of sleep. Although we can have dreams during every stage of sleep, dreams during REM sleep are more vivid. Stage V sleep can also cause phases of body movements. REM sleep, the deepest phase of sleep, takes place 90-120 minutes after the onset of sleep. It reoccurs about 90 minutes after that.