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What Happens When You Sleep?

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Sleep, a commonly regarded privilege and right for humankind worldwide. Nothing compares to getting under the covers and shutting down for the night after a day of serious work. But have you ever wondered what actually happens during sleep?

What Is Sleep? Why Do We Need It?

Most can agree, their quality of life just isn’t the same without adequate sleep. So how can it be that it can have such a detrimental impact on your health? What is sleep? 

To this day, despite all the advanced technology and research prevalent, the totality of sleep is still a mystery. Oxford Language defines sleep as “a condition of body and mind that typically recurs for several hours every night, in which the nervous system is relatively inactive, the eyes closed, the postural muscles relaxed, and consciousness practically suspended.”1 One prominent theory called the restorative theory suggests that the primary function of sleep is to allow the body to restore everything that was diminished throughout the day on a cellular level. Which is considered cellular restoration1. This restoration is articulated through muscle repair, protein synthesis,

Tissue growth and hormone release2

Another theory, called the brain plasticity theory, suggests that neuron and nerve cell reorganization happens when you sleep3. This is facilitated by waste being removed from the central nervous system. Throughout the day the waste builds up in your central nervous system and can cause your brain to act sluggish. After these toxins are flushed your cranial processes are no longer slowed down by the waste buildup. This explains why getting a good night’s sleep is crucial. The quality and quantity of sleep affect your learning, memory, problem-solving skills, creativity, decision making, focus, and concentration3

Not only is a good night’s sleep ascribed to enabling clear cognitive reasoning and cellular regeneration, but it is also a weighty factor in your emotional well-being, energy conservation, weight maintenance, proper insulin activity, immunity, and heart health3. It’s no wonder why humans treat sleep so early and just don’t feel the same without a good night’s sleep. 

The Biology of Sleep

What happens biologically during sleep? We defined above that sleep was a physiological process where the body restores, resets, and repairs itself to be fresh for the next day. There is a very specific four part cycle that sleep occurs in. Each night of sleep consists of 70 to 120-minute cycles of each of the 4 stages that are broken down into REM and non-REM3. REM stands for Rapid Eye Movement and is described as being sleep in which your eyes move back and forth rapidly behind your eyelid. Non-REM would be the antithesis of that, resulting in little to no eye movement. 

Stage 1 is Non-REM and is characterized as lasting for approximately 7 minutes when you first fall asleep. This is a light sleep where your brain waves, eye movement, and heart rate lessen3

Stage 2 is Non-REM as well and is the last stage before deep sleep. BY this stage eye brain and heart activity have already slowed down. Brain waves will spike up abruptly and then slow down drastically. At this point your body temperature lowers, eye movements stop completely and heart and muscles become increasingly relaxed. Throughout the night your body will spend the most cycles in this stage of sleep3.

Stage 3 is Non-REM sleep where the body begins to fall into a deep sleep. AT this point your brain waves come to their lowest activity level. There is no eye movement at this stage. This deep sleep stage allows your body to begin to restore itself. This phase is imperative for feeling rested and refreshed the next day3.

And lastly, we have Stage 4 of the human sleep cycle. Stage 4 is the one stage of REM sleep. Your body enters this REM sleep approximately 90 minutes after you fall asleep, or 90 minutes after hitting the sheets after a long grueling day of work3. In this stage of sleep, your breathing and heart rate increase as your brain waves and eye movements become more active3. This stage is where dreaming is most probable and is detrimental to learning and memory, as it is the stage where your mind processes all the information you picked up throughout the day. 

Side Effects Of Sleep Deprivation

Sleep is essential to the wholeness and well-being of your mind and body as reported above. But what happens to your body if you don’t get enough sleep?

Sleep deficiency is the term ascribed to experiencing one or more of the following phenomena: Not getting enough sleep, sleeping at the wrong time of day, not getting the restorative REM sleep your body needs, or having a sleep disorder such as sleep apnea or insomnia4. Whereas sleep deprivation is understood as being seriously delimited from any sleep.

Long term sleep deficiency is believed to contribute to the following health and lifestyle conditions:

  • Greater risk of developing chronic diseases, such as diabetes and hypertension
  • Trouble concentrating on tasks
  • Difficulty driving 
  • Lack of motivation
  • Increased propensity to be sedentary

Long-term sleep deprivation is associated with disorders affecting your kidneys, lungs, and heart. Sleep deprivation can also wreak havoc on “digestive, endocrine, central nervous and musculoskeletal” systems4

Not only is sleep relaxing, but it’s also a crucial factor in your long-term health and well being. Now that you know what happens during sleep, you should be all the more willing to schedule more time for sleep in your routine.

Sources 

  1. Oxford Languages Dictionary. Google 2021.
  2. John Hopkins Medicine.
  3. Healthline. ‘What Is the Purpose of Sleep’
  4. Levy, Jillian. ‘Get Some Sleep! Sleep Deprivation Causes + 6 Natural Treatments’

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Sleep trainer working in New York City in a voluntary orthopaedic practise. Also an independent medical writer and designer.
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Meet Our Review Board

Each week our team researches, writes and collaborates with industry leaders to bring you simple easy-to-read sleep information.

David Bridge

Sleep Coach

Siddhesh Tiwatne

Sleep Coach

Authored by healh experts and journalists

Fact checked and science-backed

Medically reviewed by physicians

Meet Our Review Board

Each week our team researches, writes and collaborates with industry leaders to bring you simple easy-to-read sleep information.

David Bridge

Sleep Coach

Siddhesh Tiwatne

Sleep Coach

Authored by health experts and journalists

Fact checked and science-backed

Medically reviewed by physicians

Meet Our Review Board

Each week our team researches, writes and collaborates with industry leaders to bring you simple easy-to-read sleep information.

David Bridge

Sleep Coach

Siddhesh Tiwatne

Sleep Coach

Authored by health experts and journalists

Fact checked and science-backed

Medically reviewed by physicians

Meet Our Review Board

Each week our team researches, writes and collaborates with industry leaders to bring you simple easy-to-read sleep information.

David Bridge

Sleep Coach

Siddhesh Tiwatne

Sleep Coach

Authored by health experts and journalists

Fact checked and science-backed

Medically reviewed by physicians