bigstock-Human-Head-Silhouette-6554479Sleeping might seem like one of the most relaxing things you can do for your body and mind. You can shut off your brain and body for a length of time in order to rejuvenate your energy levels and give you a clear mind. Though for this period of time you are physically asleep, your body and mind are not. Sleeping is one of the most active periods of time that your body participates in. Throughout your time sleeping, metabolic functions are being carried out, thoughts and memories are being stored and categorized, and body processes are performed. Sleep is an essential part of the active recovery of your body, and it’s vital to survival.

Sleep is a state of your body and mind, in which the normal brain wave activity differs. The changes in your brain’s wave length allow your body to restore its essential needs in order to keep you functioning normally. Along with changes in brain waves, sleep changes your heart rate, your breathing, body temperature, and other functions, like rate of digestion. Your body physically slows and focuses on energy on restoration, while your brain takes over and uses energy to keep you thinking, speaking, and remembering clearly when you awaken.

Sleeping helps you to feel rejuvenated because of the physical restoration of your energy levels. Your muscles get repaired, your blood circulates and flushes toxins, while your organs do their part to filter, absorb, and fuel your body. Restorative sleep comes in different forms, and you may have experienced several different types of sleep throughout your lifetime. Both non-REM and REM (rapid eye movement) sleep are important to your body’s needs. Sleep is normally categorized by scientists through four distinguishable characteristics; reduced motor activity, decreased response to external stimuli, posture (lying or sitting with eyes closed), and reversibility, or the ability to waken (unlike a comatose state). These four characteristics are necessary for your body to undergo non-REM and REM cycle sleep.

Non-REM and REM cycle sleep come in stages, some of which you can probably recall experiencing. A complete cycle of sleep usually takes about 1 ½ hours, or 90 minutes. Different stages of sleep are categorized by different active brain waves, and the alterations that occur when the body goes from alertness and awareness to sleep.

Stage one

Stage one of non-REM sleep is categorized by the ability to awaken easily. Stage one occurs from the time you lie down to fall asleep to the beginning of stage two. Sometimes, your body responds to external stimuli in stage one, like noises and movements. Your brain waves begin to lengthen, and you might experience random thoughts that seem normal while trying to fall asleep, but are really strange if you awaken in the middle of them. Most people agree that stage one of sleep feels like the entire time you were trying to fall asleep in the first place.

Stage two

Stage two sleep of non-REM sleep is still categorized as light sleep, and it is still somewhat easy to wake a person from this stage. More grogginess can be felt when awaken from this stage by external stimuli. Brain waves become much longer in stage two, and your body begins its restorative processes at this time.

Stage three

Stage three sleep is the step of non-REM sleep in which light to moderate sleep turns into deep sleep. Deep sleep allows the brain waves to lengthen more thoroughly. The body relaxes but the muscles maintain their tone. It is much harder to wake someone from this stage of sleep with external stimuli, unless the stimuli is meaningful or frightening to the person. Stage three sleep is relatively short, about ten minutes, and is more of a passage into stage four sleep.

Stage four

Stage four sleep is the deepest of the sleep stages. It is also referred to as REM sleep. REM sleep is the phase in which dreams may occur, and the stage can be categorized by the rapid eye movement that can be observed in the sleeping person.  The parasympathetic nervous system, responsible for all your bodily functions that are continuously performed without your control, lowers your body temperature, your breathing rate, and your heart rate. Stage four usually lasts about 30-45 minutes. The body’s restorative and healing processes are at their highest rates throughout this stage, and it becomes more difficult to wake a person from this stage as well, though the muscles maintain their tone. You may observe a stage four sleeper twitch or occasionally move.

Sleep is essential to the human body, and to all mammals at that. Without REM sleep, or the ability to sleep deeply, the body and brain may undergo severe physiological effects and disturbances, like hallucinations, psychosis, depression, and aggression. Deep and restful sleep is imperative not only to your mental health, but to physical health as well. Loss of sleep can decrease your body’s ability to fight off illnesses and diseases, cause weight gain, and cause skin to lose its elasticity. Sleep is as important to your body as a healthy diet and exercise, and is frequently overlooked in a fast-paced society.