All about sleeping

The following is a guest post of Brockwood Park School student Héloïse Nonat from France. The article is the product of a project Héloïse did for a class called Core Health & Movement, one of Brockwood’s core classes that all the younger students (aged 13-15) as well as some other students take. In the course, students were asked to pursue their own projects in the field of health and movement. Héloïse decided to do some research on the topic of sleep. 

All about sleeping

Everybody knows that sleeping is essential for mental and physical health. It is so important that we spend a third of our life sleeping. But what exactly happens in our brain and body when we sleep? Is blue light truly impacting our sleep? Why do we dream? We will talk about naps, dreams, sleep cycles and more, even if some aspects of sleeping are still a bit of a mystery.

Woman sleeping (pexels)

What happens when I sleep?

There are several stages of sleep. Five, to be precise. The first stage is the light sleep. We can be awakened easily. The muscle activity slows down as we fall asleep. During the second stage of sleep, the brain waves are becoming slower, the heart rates slows down and the body temperature falls. With the third stage the deep sleep starts. The brain waves are even slower. It is the time where people are experiencing sleepwalking, night terrors and sleep talking. The deep sleep continues during the fourth phase. The fifth phase is called Rapid Eye Movement sleep (REM). This is the time for intense dreams. Just as its name suggests, in this stage the eyes are moving fast and in all directions. Your brain is more active and your heart rate and breathing increase.

There are 4 to 5 dream cycles a night. In each cycle, the order of phases above is not respected. It would rather be phases 1, 2, 3, 2, 1 and REM. We dream four to six times a night, for around twenty minutes each time.

While sleeping, the brain clears the toxins created during the day. The cells connections made during the day are strengthened, and the useless one are cancelled. This is why you are more likely to remember a lesson when you read it once before turning off the light.

When we sleep, muscles and tissues are restored and grow, the body synthesizes hormones.

Are naps good for my health?

Studies have shown that taking a nap improves the mood. We are less impulsive and better able to deal with frustrating events. We also work more efficiently. But it has also been revealed that people who nap are more likely to develop long-term chronic conditions. Another bad effect of naps is the grogginess experienced after it (called sleep inertia). So what should you do? It seems that a twenty to thirty-minutes nap has more benefits than drawbacks if you don’t feel groggy afterwards.

What would happen if I didn’t sleep for several days?

That is the question sixteen-years-old Randy Gardner asked himself in 1965. With the help of two of his friends, the high-school student stayed awake for eleven days and twenty-four minutes. Researcher William Dement from Stanford University made plenty of experiments during these eleven days. This experiment allowed the scientist to look at how extreme sleep deprivation is affecting our body. From the second day on, Gardner started to struggle with eye focus. He was not able to repeat simple tongue twisters anymore. As the days were passing, he also experienced concentration troubles, short-term memory troubles, paranoia and irritability. During the last day, he was expressionless and spoke without intonation. His mental abilities were diminished.

Sleep deprivation causes approximately 20 % of all car accidents. An average of 1,500 people are killed each year in the U.S due to the lack of sleep when driving.

What is the problem with watching TV before going to bed?

One part of the problem is the mental activity that keeps us awake, but this doesn’t explain everything. The blue light emanating from laptops and televisions screens, but also LEDs, has bad effects on sleep. During the day, our eyes receive blue light from the daylight. At night, this reception of blue light stops and the body starts producing melatonin. This hormone regulates our internal clock that makes us feel sleepy at night. But while standing in front of a screen, the eyes keep receiving the blue light and hence we don’t produce melatonin. This affects our body clock and make us unable to sleep. The scientific name for this internal clock is circadian rhythm. The brain’s circadian clock is located in the hypothalamus. This area of neurosciences, called chronobiology, is still being explored. Notably, the 2017 Nobel Prize of medicine was awarded to three American scientists who researched about the molecular mechanism controlling internal clock.

This picture shows the circadian rhythm and how it regulates our body (wikimedia)

So, for how long should I sleep?

Everyone has different needs, but for most people eight hours of sleep a day seem to be enough. It varies with age, as babies and teenagers need more time to sleep. As an example, people sleep on average seven hours and ten minutes a night in the United Kingdom.

For an optimum sleep, the room should be between 16°C and 20°C.

As a conclusion, we have seen that many studies are focusing on sleep, but we still need to discover a lot of things, especially about the intriguing world of dreams. We still have to find out why we dream, if there is a meaning to our nightmares and dreams, and many other exciting questions.

Videos to learn more about sleep:

Russell Foster: Why do we sleep? | TED Talk |

How Much Sleep Do You Actually Need? – YouTube

The 2017 Nobel Prize of Medicine (about circadian rhythms):

Guardian: Nobel Prize in Medicine awarded for research on circadian rhythms

About circadian rhythms:

TED-Ed: How does your body know what time it is?

Theories about why we dream:

TED-Ed: Why do we dream?


  • Sleep better by Graham Law and Shane Pascoe (2017)
  • “Why do we sleep?” (

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