Understanding the 5 Stages of Sleep and Sleep Cycles

Sleep is the most important factor for our mental and physical well-being. There is a biological clock in every living cell. Sleep is more essential than food for life. Animals die of sleep deprivation before starvation. 

Sleep Process

To start sleep process, pineal gland in the brain pumps melatonin. Then brain shuts itself to outside stimulus and turns inward. When we are falling sleep, short and strong contractions of the body parts start. Brain cells begin processing and registering daily information. Our immune system gets boosted during the good night sleep.

sleeping woman


5 Stages of Good Sleep 


It is the first 5 minutes of shallow sleep. There is no significant change in body the body yet.



Deep parts of the brain send electrical signals to knock down the cortex of the brain. The higher amount of these electrical signals predicts better performance for the next day. At the molecular level, memories are created or reinforced during this stage. It could last up to 50 minutes.

sleeping couple



The deep, coma like stage, which is essential for brain to recuperate. The cells start producing growth hormone which is essential for bone and muscle health. It makes you feel vibrant and healthy. Pain receptors become inactive. This is the stage you won’t easily wake up.



The muscles are fully relaxed, mental activity almost stops. The brain activity form is similar to coma patients. It could last up to 30 minutes.

The Stages 1 - 4 are repeated before going to REM stage of the sleep. The whole cycle is repeated 4 - 6 times before we wake up.

sleep stages cycles



This stage is the most critical stage for survival. Rodents deprived of REM sleep die after just 5 weeks. Mostly 20 - 30% of a night's sleep is REM session in adults. Fifty percent (50%) of newborn’s sleep is REM sleep.

Distinctive eye movements, engorgement of sexual organs happen in this stage. Dreaming takes place in this phase. It is believed that everyone dreams but some don’t recall it. Body becomes unable to regulate temperature and blood pressure in REM stage. But it is not coma-like stage as Stage 4. Brain stays fully active in REM stage. The muscles in the eyes and ears are activated, the eyeballs move from side to side. Systems in the brain stem are completely shut down. Serotonin production stops in this stage.

End of REM Stage is marked with brief wakening. When light comes through eyelids and touches retina, wake-up signal is sent to the brain.

sleep stages in box form



  Author: Dr. Tina Ureten

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