Why we sleep and what is happening in our body at night

By Vladimir Marchenko

1. Why do we need sleep
2. How important is sleep at night
3. What does sleep consist of
4. What happens in the brain during sleep?
5. "Sleep is not an absence of activity, it is a different type of activity"

Almost a third of our life do we spend sleeping. Rest is a very important component of a successful life, and a lack of it even for several days can seriously affect human health. Why do we need to sleep and to which extent?

Why do we need sleep

The exact role of sleep in human health is not very well defined yet. One of the main hypotheses says that sleep is necessary for renewing the body's resources: resting, recharging the brain (memory reactivation), producing hormones, strengthening the immune system, normalizing metabolism, healing wounds, restoring skin damage, etc. In fact, it means the body needs some "quiet" time to regulate the occuring internal processes (for example, lower the blood pressure), and it’s important that nothing distracts it. Sleep can be compared to routine maintenance or stock-taking when everything unnecessary is removed while useful items and resources are distributed around the body or used to restore the systems.

The evolutionary mechanisms associated with sleep in relation to Homo sapiens species is a little contradictory. An eight-hour sleep mode made a person vulnerable to predators and the forces of nature, nevertheless, evolution has fixed this very mechanism of rest. Moreover, it is the duration of sleep that has become a novel evolutionary mechanism. Most animals, on the contrary, do not have a pronounced sleep-wake cycle and are used to take multiple naps during the day. Possibly, the transformation of the sleep cycle in humans is associated with the development of brain capacity and activity (especially memory). Hence, sleep is necessary for maintaining physical and mental health.

How important is sleep at night

Lack of sleep increases the risk of developing stress, which in its turn can cause diabetes, heart disease, obesity, depression, disorders of the nervous system and short-term memory, etc. It affects both the body and psyche: you feel tired and sleepy, the eyelids literally stick together, you can’t think clearly, and it is impossible to concentrate. If you continue with the lack of sleep for several days in a row, you shall start experiencing a sharp change in mood, the levels of stress hormones adrenaline and cortisol rise, as well as the blood pressure. In the longer term, paranoia and hallucinations about non-existent objects and entities can develop. Overall, people who don’t sleep enough are more nervous and get sick more often.

The duration of sleep for every specific person changes throughout life or under the influence of certain circumstances (moving house, having a child). In general, the recommendations for average sleep duration are as follows:

• Newborns - up to 17 hours;
• Children - 10-12 hours;
• Teenagers - 8-10 hours;
• Adults - 7-9 hours;
• Elderly people - about 6-7 hours.

What does sleep consist of

Unlike many people think, studies about sleep indicate that the brain does not switch off during sleep but continues to function. Sleep is also not a homogenous process, and two phases of it, slow (deep) and fast, continuously alternate.

Deep sleep (NREM) accounts for approximately 75-80% of total sleep duration. This period is characterized by slow brain waves, calm and deep breathing, and muscle relaxation. It is at this time that the brain sorts out everything perceived during the day and redirects the most important things to the long-term memory. What concerns the physiological level, poorly formed synaptic connections are also removed.

REM phase takes 20 to 25% of the total sleep duration. During it we see dreams lasting from tens of seconds to an hour. By the end of the night, the phase becomes longer, as well as the dreams themselves. However, after waking up, a person remembers only a little about the plots of dreams, which is absolutely normal. During REM sleep the brain is at the peak of nocturnal activity, the muscles (except for the respiratory and oculomotor muscles) are almost completely paralyzed, the heart rate increases, and breathing becomes uneven. In the REM phase, the processes of memory reactivation and learning are completed, the “library” of knowledge and memories is finally formed.

What happens in the brain during sleep?

According to the concept of C. Saper, a professor of neuroscience at Harvard University, sleep is controlled by a network of several interconnected nodes that are tied to a 24-hour daily cycle and "switch" the body to sleep or wakefulness. Accordingly, it consists of inhibition and excitation systems.

The basis of the inhibitory system is the ventrolateral preoptic region (VLPO), located in the anterior part of the hypothalamus. It is connected with the wakefulness system and, if necessary, supplies there a "brake fluid" - gamma-aminobutyric acid (GABA), which suppresses the activity of neurons by increasing the gap between receptors. In this case, the neuron cells become less sensitive to electrical signals and “calm down”.

The excitation system is dominated by nerve nodes that make up two parallel bundles. Excitation waves run through them to the cerebral cortex. In a so-called "bluish spot" a significant part of the main neurotransmitter norepinephrine is produced. The injection of norepinephrine, which is also responsible for the feelings of fear and panic, occurs instantly, so, frankly speaking, there is absolutely no point in getting more sleep in the morning after the alarm goes off. Although, this method of awakening may be suitable for some people.

However, the impulse component of sleep is only a part of the mechanism involved. It is supplemented by a so-called biological clock in the form of a melatoninergic system, which also works automatically. If light enters the retina, it passes through the suprachiasmatic nuclei of the hypothalamus and then enters the pineal gland (it can be compared to the light sensor in electronic devices). In the pineal gland, the hormones melatonin and serotonin are produced. With the onset of darkness, melatonin begins to inhibit the suprachiasmatic nuclei of the hypothalamus, signalling that it is time to sleep. Serotonin, in turn, helps a person feel refreshed upon waking up.

These systems were formed before the invention of any gadgets, so it turned out to be quite easy to deceive them with artificial light. That’s why certain dissonance occurs in the body when during the night time a bright light hits the eyes. As a result, melatonin is not produced, circadian rhythms are disrupted and that’s why a person cannot fall asleep for a very long time. Therefore, it is better to go to bed without any devices.

How long different animals sleep:

Some interesting facts about sleep

• the record for the number of days spent by a person without sleep is 11 days and 25 minutes (and we do not recommend repeating!);
• the most sleepy animal is the little brown bat, which rests 18-22 hours a day;
• people, animals and insects all suffer from sleep problems. This usually leads to fat gain and loss of balance;
• the peak of drowsiness in humans occurs at 2 pm and 2 am;
• an ideal dream lasts about 26 minutes;
• residents of the Netherlands, France and Great Britain sleep the longest;
• 75% of people have colourful dreams;
• classical or ambient compositions (and other calm electronic music) with a frequency of 60-80 beats per minute are best for falling asleep;
• in almost half of cases, sleeping with a pet decreases sleep quality;
• birds in a migrating flock periodically fly into its centre to take a nap. At this time, they only slightly flap their wings and follow the air stream created by the flock.

"Sleep is not an absence of activity, it is a different type of activity"

As we just discussed, sleep is not a passive state, during which a person just "turns off". Many processes in the body continue to occur and even the communication with the outside world is partially preserved, and this is how the theory of sleep learning (hypnopedia) emerged. Although it was not possible to fully develop the technique of acquiring knowledge at night (learning a new language from scratch or studying during sleep is still not possible), some of the main ideas and working concepts based on the most recent scientific research were implemented in a new Hypnopedia application.

Hypnopedia free sleep app for iOS is a “3-in-1” sleep complex. The first part is relaxing sounds that you can switch on just before going to bed. They are composed of sounds of nature and melodies that tune you to sleep and can be combined into individual playlists according to your tastes. They can also be regulated by volume: general or relative to each other.

At night, the main feature of the app - sleep-learning affirmations - come into play. They are short, motivational statements, sufficient to be perceived during a certain sleep phase, devoted to various topics, from self-awareness to building confidence. Affirmations do not awaken the user, but are perceived on a subconscious level and have a beneficial effect on his mental health. The brain assimilates them as important pieces of information and directs them to long-term memory.

The night session ends with a smart alarm clock that gently wakes you up in the time interval defined by you before you went to bed. Thanks to the information received from the Apple Watch sensors, the application algorithm selects the best moment for awakening, after which you do not feel sleepy. In this case, the alarm clock simply vibrates on the wrist, without interrupting the sleep with any sharp sounds.

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Thus, sleep is an important component of human life. Sleep deprivation affects the body more acutely than the lack of food or water, and that’s why it should by no means be neglected. Being able to wisely regulate and improve the quality of your sleep will allow you to restore better, and Hypnopedia free relaxation app can help you with it.