Often a person does not even imagine what is happening to his body, brain, how blood pressure and breathing change, while ordinary sleep lasts. Meanwhile, when he sleeps, complex work does not stop in his body for a moment, which entails very curious changes in the state of health, well-being and even consciousness.
Despite the close attention of scientists, sleep is still largely a mystery. Science recognizes it as an “absolute necessity” for man. Moreover, it is known for certain that lack of sleep (and, possibly, its excess) negatively affects the state of people’s health, increasing the risk of many pathologies, including:
- type 2 diabetes;
- obesity, etc.
While sleep continues, the body and brain are working, “repairing” themselves after the past working day and preparing for the upcoming one.
A lot of amazing metamorphoses take place with the human body at this time.
A person’s sleep throughout its duration has several stages that form a cycle. Not all stages are equal.
- Falling into the power of drowsiness, people fall into a very light sleep, which then deepens.
- The cycle begins with the so-called non-REM sleep (Stage 1 Non-REM sleep). It is characterized by smooth movements of the eyeballs and usually lasts no more than 10 minutes.
- Then there is a transition to a deeper stage (stage 2 Non-REM sleep). It lasts an average of 20 minutes.
- Then comes the turn of the 3rd Non-REM sleep and the deepest 4th stage of Non-REM sleep or delta sleep, also related to slow sleep.
- Following this, the cycle returns to the second stage and ends with a stage called REM sleep or REM sleep. It lasts only about five minutes and is accompanied by rapid movements of the eyeballs and intense (with incredible speed!) The work of consciousness, thanks to which dreams are born, sometimes “prophetic” or giving answers to the most difficult questions for a person.
The entire sleep cycle usually takes 90 to 120 minutes. Therefore, during the night, sleeping people go through four or five such cycles, waking up for only one second. However, they usually do not even realize that they are awake! This occurs after the end of the REM sleep stage, before the start of a new cycle beginning with Non-REM stage 1. At the same time, the 3rd stage of deep slow sleep is reduced and the duration of REM sleep is lengthened.
“During the night, as the number of sleep cycles increases, the body spends less time in deep stage 3 Non-REM sleep, so it is not uncommon for a person to wake up in an alarm state in the middle of a bizarre dream,” says Sigrid C. Veasey, neuroscientist, professor of medicine at Center for Sleep and Circadian Neuroscience at the University of Pennsylvania.
“We don’t know why, but periods of REM sleep do get longer as cycles change,” says Daniel A. Barone, MD, assistant professor of neurology at Weill Cornell Medical College. One theory, he says, is that REM sleep prepares the human body for awakening.
The famous American prose writer John Steinbeck argued that the “sleep committee” was able to solve the most difficult daytime problems overnight. One cannot but agree with him, since every person (more than once!) Benefited from the painstaking work of this “committee”.
The human brain stays in “work mode” all night, especially during REM sleep, when it’s almost as active as when it’s awake. He is busy processing new information. The brain “sorts” everything that it received during the day and filters out the unnecessary.
According to a new scientific theory, it is possible that connections between brain cells are strengthened or weakened during sleep, depending on how actively they were used during wakefulness.
While a person is sleeping, his brain can do another, very important thing — to get rid of the accumulated “garbage”. And this is one of the freshest and most exciting scientific ideas about sleep tasks.
A 2013 study in mice found that the waste disposal systems in the brain are more active during sleep. Scientists have theorized that humans sleep to give the body time to clear the brain of toxic by-products that would otherwise accumulate and cause a variety of problems and disorders down the road, including Alzheimer’s disease.
Changes in breathing and heart rate
All kinds of normal physiological processes slow down when a person falls asleep. Breathing calms down, the rate of contraction of the heart muscle decreases, all organs “slow down” their work.
Sometimes, normally, during sleep, a person’s breathing is interrupted for a few seconds. When such pauses last more than 10 seconds and occur more than 9 times per hour, we are talking about sleep apnea syndrome.
Decreased blood pressure
When a person falls asleep, the general relaxation of the body is accompanied by the expansion of blood vessels. As a result, blood pressure decreases, reaching its lowest level between 0 and 4 a.m., during stage 3 non-REM sleep. By 5–6 o’clock in the morning, when the body is preparing for the moment of awakening, it returns to normal.
In absolutely healthy sleeping people, an average decrease in blood pressure by 5–7 points is recorded. And this is considered the norm.
However, if a person’s blood pressure drops sharply by 20 or more mm Hg during sleep. Art., we can talk about a serious pathology:
- internal bleeding;
- endocrine disorder;
- inflammatory disease;
- kidney disease, etc.
If blood pressure indicators do not decrease, but increase at night, there is a significant risk of developing hypertension.
Decrease in body temperature
One of the most common tips found in popular science articles on the topic “How to improve sleep?” Is the recommendation to sleep in a cool room. It has a scientific basis.
The fact is that the cool atmosphere of the room imitates what happens to the body while a person is sleeping: his body temperature drops slightly. Therefore, airing or air conditioning the bedroom before going to bed helps to ward off insomnia.
During stage 3 REM sleep, the human body can cool down by 0.5–1°C. This usually happens around 2–3 am. By the time of awakening, the temperature returns to normal.