There are two main types of sleep: natural and artificial.

Naturally called sleep, coming in humans and animals spontaneously, i.e., without any extraneous impact.

Artificially called sleep, caused by chemical or physical factors (narcotic sleep, electric, hypnotic) L
Natural sleep of an adult person and most animals is characterized by periodicity, however, the duration of periods and their alternation can be very different.

Adults are usually filmed at night and are awake during the day. Such a dream is called monophasic. Some people sleep twice a day – at night and additionally during the day (two-phase sleep). Most pets (dogs, cats, cows, horses) have a polyphasic sleep: they fall asleep and wake up several times during the day and night, without strict adherence to regularity in the alternation of sleep and wakefulness. In children, polyphasic sleep prevails. Newborns spend most of their time in sleep. Their sleep is interrupted several times a day due to the feeling of hunger, but with age, under the influence of the environment and upbringing, the rhythm of sleep is reconstructed and gradually approaches the rhythm of sleep of adults.

The duration of artificial sleep can be adjusted by dispensing the effects of the factors causing it (hypnotics, electric current, etc.).

The duration of periods of natural sleep in animals of different species is very variable, and even in the same species of animals, it can differ dramatically in different seasonal periods.

Of particular interest from a physiological point of view is the so-called seasonal hibernation of animals, widely distributed in wildlife.

Reasons for the frequency of sleep. “The biological clock”

As we have already seen, periodicity is characteristic of the natural sleep of animals and people, although the duration of these periods can be very different. What is the reason for this frequency? In relation to the seasonal hibernation of animals, we have already concluded that its periods are due to unfavorable seasonal conditions. Well, what about a person’s dream? Why in the whole world do most people sleep at night and stay awake during the day? Is it possible to alter this rhythm and how durable is it ? Is it only day and night (i.e. light and dark) that determine the rhythm of sleep and what is the situation, for example, in the conditions of the polar night?

All these questions are of great interest. Especially in our century, when space ships, submarine nuclear boats are sent to distant and long voyages. For the answer, we should remember the distant past, the days when cavemen when darkness hid deep from random encounters with dangerous creatures, capable of seeing at night, which could determine in advance the outcome of an unequal struggle. Only at the onset of dawn did man regain his advantage over the animal world, creating primitive tools and other forms of influence on nature.

Thus, light and darkness, in other words – the alternation of day and night, is one of the main biological rhythms that shape the behavior of humans and animals.

But this is not the only rhythm. In nature, there are multiple “biological clocks” in duration, counting one or another cycle of time and related phenomena. In our body, many processes take place cyclically in accordance with the rhythm of sleep and wakefulness. Cycles of biological rhythms are short and long one-year (reproduction cycles in many animals and plants), monthly (for example, marine organisms rise from the depths to the sea surface at full moon), diurnal, so characteristic of human activity, etc.

Scientists have noticed that most of these cycles coincide with the rhythms of inanimate nature, due to the rotation of the Earth and its movement around the Sun. The alternation of light and dark (day and night) is primarily due to these phenomena, and with them – the alternation of sleep and wakefulness in humans. All other processes in the body are closely associated with these states: physical activity, food intake and associated secretions of digestive juices, excretory processes, etc. They are timed to a certain hour in early childhood under the influence of a certain mode of life in the family, in children teamwork. That is why the violation of the rhythm of sleep and wakefulness in the adult state is difficult to tolerate. It was especially well experienced by those who had to move or fly to cities separated by large distances in the east-west direction.

Despite the unpleasant state when changing the rhythm of sleep and wakefulness, some people whose work is connected with night time are forced to “change” day to night, that is, to sleep during the day and stay awake at night. Over time, they become accustomed to an altered rhythm, but because of their surroundings or because of their biological nature, people still want to keep their sleep closer to night, and wakefulness to daytime hours.

In connection with the preparation for space flights, in which the sense of the circadian rhythm can be lost, in a number of countries observations were made of the time sense of people who were in a closed room, which let in natural light. These observations showed that over the course of time, their duration of sleep and wake cycles was somewhat disturbed, but the basic rhythm was maintained. Newbies who fall into the conditions of the polar night experience the same. However, in all these observations, the production activity of people, the fulfillment of a certain task were of great importance.

Theoretically, it can be assumed that a day can be divided into shorter intervals (for example, into four periods) with alternation of shorter sleep and wake cycles. According to some scientists, this seven -hour duration is not due to any special need of body functions. Nevertheless , by virtue of a certain way of life of human society as a whole, it seems that breaking the usual way of life is hardly advisable.

How much time do I need to sleep?

This question worries a lot of people, especially young people. Still would! Modern life, with its rapid pace, extraordinary emotional intensity and many-sidedness of vital interests, involuntarily makes one regret the time “lost” to sleep.

After all, even in the relatively recent past, when before . It took dozens of days to go from Moscow to the Crimea or the Caucasus, respectively, and time was measured by other standards. Then there was a natural appearance of the Oblomovs with their measured-drowsy existence.

But now, when you can get from Moscow to Paris, London or the Caucasus in three to four hours, isn’t it a shame to spend seven or eight hours every day in a dream? Is it possible to reduce this time? Or somehow it is more rational to distribute it – to sleep when, by the will of circumstances, we are doomed to “doing nothing”. In a word, is it possible somehow to “ snatch ” an hour or two from a night’s sleep with the help of science ?

Lack of time is familiar to many. She experienced almost all the students during the exams. And not only during the exams! In adolescence, so much I want to see, learn, feel! But, unfortunately, only 24 hours a day …

How much sleep is minimal? Observations show that the need for sleep in individuals is different, especially in people of different ages. If newborns sleep about 20 hours a day, then the child, aged between six months and a year, sleeps about 14 hours a day. After four years, children are recommended to sleep for 12 hours, and at the age of ten years – at least 10 hours a day. For older school age and for adults, 7–8 hours a day are considered the norm of sleep. In old age, people sleep even less, sometimes only six hours of sleep.

Of course, there are deviations from these common truths. There are people who, leading a very active lifestyle, systematically slept much less. We heard that, for example, Napoleon, Peter the Great slept 5-6 hours a day and, despite this, they retained tremendous energy and efficiency.

However, such people are a rare exception. In most cases, for a period of time, one can limit oneself in the duration of sleep, but, as a rule, this is accompanied by an increase in irritability, a decrease in efficiency and a completely overwhelming need to sleep.

Therefore, saving yourself a dream does not justify. Better save time on friend , in particular, so organize their work, leisure and recreation, to get a significant gain in time.

Along with this, it is very important to follow the rules of sleep hygiene. Then a short sleep can give better rest. About what should be the hygienic conditions of sleep, will be discussed below. And now we will proceed to the consideration of what is commonly called dreams.