woman sleeping

How Sleep Works: Diving into the Science of Sleep

Sleep has been a subject that scientists, psychologists and other specialists have continued to study through the years. Even though it’s an essential function of the human body, a major aspect of sleep still remains a mystery.

For years, researchers involved in sleep science have discovered that multiple parts of the brain are involved in the processes of inducing chemicals and hormones that governs sleep, thus making it an incredibly complex subject.

Some aspects and mechanics of sleep (and what happens to the brain in our dormant state), however, have been slowly uncovered by years of research. This provides insights into how sleep affects our cognitive, physical and emotional functions, as well as how we all can get better sleep.

Why Do We Need Sleep?

An average person spends about a third of his or her life asleep. Sleeping is as important to us as eating and breathing. If we get nutrition from eating, then we heal our body during sleep. Although why humans need sleep to regenerate is still a mystery. Couldn’t we just turn off one part of our brain, like whales and dolphins do?

man sleeping

One thing’s for sure, our brain definitely needs sleep mainly to process and organize itself.

Located in our hypothalamus is a cluster of cells called the supra-chiasmatic nucleus (we’ll talk more on this later). When our body is exposed to light, this triggers our body to release hormones like cortisol, which keeps us awake. But when it’s dark, the body suppresses the release of cortisol and triggers the release of melatonin instead.

Some scientists suggest that sleeping may be a way to conserve energy. Humans need much less energy when asleep, and because bodily functions rely heavily on storing calories, it’s said that sleep is a way to keep our body from burning calories.

Another reason we sleep is to heal our body. When we grow muscle tissue, growth hormones are released and we synthesize protein. Research indicates that although our body can restore and heal itself when we’re awake, it does so faster while we’re asleep. It’s also the time when our brain rests and reorganizes itself. This theory is known as brain plasticity.

What Happens During Sleep?

Our bodies have an internal time keeping device that’s synchronized to the rising and setting of the sun, this internal clock is called circadian rhythm. This keeps our bodies in sync with day and night cycles.

Our circadian rhythm is established during the first months of life and controls other biological patterns like body temperature, blood pressure and the release of hormones. So, it’s understandable that if we mess with our body’s internal clock, it wouldn’t turn out so good for us because that’s just how we are programmed since birth.

Circadian means “a day” and this particular rhythm affects all living creature’s eating, sleeping and mating habits.

So what part of the brain controls sleep?


In humans, the main regulator of circadian rhythm can be found in the hypothalamus. A small area in your brain that’s responsible for connecting the nervous system to your endocrine system.

Our internal clock is dictated by a group of nerve cells in the hypothalamus called the suprachiasmatic nucleus or SCN. This is connected to our optic nerves, which then allows the SCN cells to respond to night and day or brightness or darkness.

When our optic nerve senses light, our SCN cells send signals to raise our temperature, heart rate, blood pressure and delay the release of sleep hormones like melatonin.

Studies found that when our bodies rise to alertness in the morning, our memory, concentration and alertness also rises so we tend to be at our cognitive best in the morning. Meanwhile, in the afternoon, we tend to feel sleepier since the time between 2 pm and 3 pm draws out our desire to sleep. However, that’s a natural part of our daily rhythm.

In the evening, the SCN picks up the signal of night or lack of light from our eyes, our organs shift into low gear and our body temperature cools. Sleep induced hormones are then activated.

Our body functions perfectly like clockwork, however, everyday disruptions, like studying late at night, pulling an all-nighter at work or staying up to finish that series on Netflix, can harm our natural rhythm, and lead to health issues like obesity, depression, diabetes and dementia.

Researchers believe that up to 15 percent of our genes may be regulated by circadian rhythms. Not only does it regulate sleep schedule in humans, in nature, it governs all types of activities from DNA replication in fungus, to leaf movement in plants and feeding time in bees.

How Sleep Works: Stages of Sleep

When we fall asleep, our bodies begin cycling through two alternating sleep phases. These two types of sleep are: rapid eye movement (REM) sleep and non-REM sleep. Both are linked to specific brain waves and neuronal activity. The human body cycles through these phases several times a night, with each cycle lasting for around 80 to 100 minutes.

kid sleeping with stuffed toys


Stage 1 (non-REM) is considered as light sleep, it’s the stage where you just entered sleep. It’s  a short period where your heartbeat, breathing, and eye movements are slow, and your muscles go into relaxation followed by bouts of light twitches. Expect your brain waves to slow down.

Stage 2 (non-REM) is where we spend the most time. In this stage, we’re about to enter deeper sleep. Our eye movement stop and our temperature drops.

Stage 3 (non-REM) is where your body starts repairing and restoring energy. Your heart rate and breathing drop to their lowest levels of the night.

Stage 4 (REM sleep) is the stage that occurs 90 minutes after falling asleep and where your eyes move rapidly. Your muscle tone will drop to the lowest point during the night. The brain activity sets the stage to more vivid dreams in REM sleep which is also important for storing memories and processing emotion. It’s also the most regenerative stage of sleep out of the four.

How Much Sleep Do We Really Need in Life?

The ideal amount of sleep will vary depending on the age groups. Children between ages 3 to 5 years old will need 10 to 13 hours of sleep. Those who are 6 to 13 years old will need nine to 11 hours of sleep.  Teenagers between 14 to 17 years old will require eight to 10 hours, whereas adults should get seven to nine hours of sleep a day.

Interestingly, the average person, with a lifespan of 75 years, spends about 25 years of their life sleeping.

Researchers have performed studies indicating that lack of sleep can cause dizziness and disorientation. Meanwhile, getting the proper amount of sleep will maximize a person’s performance and decrease cognitive issues.

Try to always get a good night’s rest. If you can’t fall asleep, then do things like listening to music or reading a physical book (kindle works too, but avoid gadgets that emit blue light). If you find yourself unable to sleep in several days, see a physician.

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