The Stages of Sleep by Hannah Tomes

What is sleep? Sleep is defined by Cambridge Dictionary as the resting state in which the body is not active and the mind is unconscious (Cambridge Dictionary, n.d.). But why do we sleep? Sleep is required for our bodies to restore, conserve energy, and consolidate. Normally the human body needs around 8 hours of sleep so our bodies can function at their best (Field, 2009). Now, what if I told you that there are different phases of sleep? Five of them to be exact. Four of them are in the Non-REM and the other stage is REM (Rapid Eye Movement). Our brain does not actually shut down when we are sleeping. Many parts of the brain are still activated while our bodies are at rest (American Sleep Association, n.d.).

Stage One Sleep- This is a very “light sleep” which the average person can be quickly aroused. In this sleep stage, “our eyes move very slowly and muscle activity slows”. During this stage, some people may experience “hypnic myoclonia” or “hypnic jerks” which feels like you are falling (American Sleep Association, n.d., para. 4). Dreaming is quite uncommon during stage one. Although the heart rate will decrease, breathing stays regular. This stage makes up for only 5% of all the stages of sleep (Mastin, 2013b).

Stage Two Sleep- This stage is deeper than stage one but people can still be easily awakened. When entering this stage our eyes quit moving and our brain waves slow down. This is the stage where naps fall into place. Stage two boosts our memory and concentration. Stage two is known to make up for about 45-50% of all the stages of sleep. That is because humans go in and out of this stage so many times throughout the night (Mastin, 2013b). 

Stage Three Sleep- In stage three it becomes hard to awaken the person asleep. The waves in the brain called “delta waves” start showing up along with other small waves. This stage makes up around 15-20%. “As well as neuronal activity, brain temperature, breathing rate, heart rate, and blood pressure are all at their lowest levels” (Mastin, 2013b).

Stage Four Sleep- This stage of sleep is the deepest level. Delta waves are by themselves in stage four. During this stage, it is very hard to awaken the person just like stage three. Together stages three and four are called deep sleep. No muscle activity or eye movement within these two stages. “Some children experience bedwetting, night terrors, or sleepwalking during deep sleep” (American Sleep Association, n.d., para. 6).

REM Sleep-  During this stage, the eyes quickly move. This is the stage that dreams appear in. The brain is more active than the other stages. The pons is in control of the REM phase. REM is important to process information learned throughout the day. This can help strengthen memory. Breathing is increased and the pace becomes irregular. The heart rate and blood pressure of bodies can increase to the level as if one was walking (Mastin, 2013a).

According to the American Sleep Association (n.d.), we spend 50% of our sleep time in Stage 2, 20% in REM, and the other 30% in the other 3 stages. Infants, on the other hand, spend approximately 50% in REM. The amount of sleep we need every night depends on our age. Sleep is important for our minds and bodies so they can work properly the following day.

References

American Sleep Association. (n.d.). What is sleep? Retrieved February 22, 2017, from https://www.sleepassociation.org/patients-general-public/what-is-sleep/

Cambridge Dictionary. (n.d). Definition of sleep. Retrieved February 22, 2017, from http://dictionary.cambridge.org/us/dictionary/english/sleep

Field, A. (2009, January 14). Why sleep is so important. Harvard Business Review. Retrieved February 22, 2017, from https://hbr.org/2009/01/why-sleep-is-so-important.html

Mastin, L. (2013a).  Sleep. Retrieved February 22, 2017, from http://www.howsleepworks.com/types_rem.html

Mastin, L. (2013b).  Types and stages of sleep. Retrieved February 22, 2017, from http://www.howsleepworks.com/types_nonrem.html