Perhaps, for many, the existence of such a hierarchical model of human needs, like the Maslow pyramid, is not a secret. And although she is criticized in every possible way, one can not argue with one: an American psychologist has clearly shown that satisfying the lower needs is a necessary condition for the higher ones to be satisfied. We will talk about one of these needs.

So, a dream!

Each person necessarily though anyhow sleeps is obviously. But we all do it in different ways. Some will prefer to lie down early in a warm crib, then to rise with the first rays of the sun, while others will hardly open their eyes only at noon, they will pass out until evening, and at night they will fully function.

With this in mind, certain patterns of alternation of activity and passivity developed over the course of a day - chronotypes, according to which we can refer ourselves to "owls", "larks" and even "pigeons". And the cyclic changes in the work of organs, systems and the organism as a whole are called biorhythms. There are three groups of biorhythms, which differ in characteristic time intervals, for which one complete cycle is performed:

Circadian - biorhythms with a daily periodicity. This includes cycles of sleep and wakefulness, as well as diurnal fluctuations in body temperature, the level of hormones in the blood, and so on.

Infradian - the duration of the cycle exceeds a day (weekly, monthly, annual rhythms). For example, the menstrual cycle or seasonal changes.

Ultradian - the duration of the cycle is less than a day (hour, minute, second rhythms). This group of biorhythms includes such short-term processes as food intake, respiration, digestive system work, hearts and activity rhythms of various pacemaker cells.

The most curious for us are circadian (circadian) biorhythms: they are also called a biological clock. And if you think that they are inherent only to people, then you are mistaken: such biorhythms are present in animals, plants, mushrooms and even cyanobacteria. After all, they provide the maximum opportunity for each species to adapt. The most important role in the synchronization of circadian rhythms is played by the daily fluctuations of illumination, therefore it is the visual system that actively participates in their regulation.

How does the circadian system work?

The answer, as always, is hidden in the brain. Let's pay attention to the following structures:

The hypothalamus regulates changes in the level of hormones in the blood, increased or, on the contrary, a weakened sense of hunger and so on. This is the very "center of sleep".

Suprachiasmatic nucleus (SCN): the core of the anterior part of the hypothalamus controls the release of melatonin in the epiphysis and is responsible for synchronizing the work of the "biological clock" of the organism.

In the epiphysis, known to us as well as the pineal body, melatonin is produced, responsible for the regulation of circadian rhythms, and their synchronization with the rhythm of the illumination of the environment.

On the back of the retina are ganglion cells that react to changes in light and contain a pigment melanopsin. With a change in the electrical activity of these cells, they receive a signal to the suprachiasmatic nucleus of the hypothalamus, from where it travels through the fibers of the sympathetic nervous system to the epiphysis to regulate the daily synthesis of melatonin.

From all this it follows that a failure in the operation of this system can be caused by both internal and external factors, and it is extremely important to monitor this! Desynchronosis, or violation of biological rhythms, not only accompanies oncological diseases, but also causes them.

Returning to seasonal rhythms ...

There is an affective disorder, such as seasonal depression. It's easy to guess what it is, right? In certain seasons (as a rule, in autumn-winter, less often-spring-summer), a person becomes irritable, nervous and unsociable, resembling a bear in a period of hibernation. According to WHO, every fifth person living on the planet faces this problem.

In winter, the light day decreases, and therefore the neurotransmitter serotonin, responsible for our mood, is produced much less. This is also due to the vitamin D deficiency produced by our body under sunlight, as it plays an important role in the production of serotonin. Melatonin, on the contrary, begins active development, which is usually suppressed by bright light. In autumn and winter, this does not happen, so the level of melatonin becomes high, causing unwanted fatigue and drowsiness. And there are simply light-dependent people who suffer a lack of sun heavier than others.

If everything is clear with the autumn-winter depression, then it's a bit more difficult with the spring-summer, after all, it would seem, there is a lot of light and even more - so what's the matter? Indeed, there is more light, but an excess of serotonin can cause the same effect as its deficiency.

So, human biorhythms are a very important but fragile mechanism, just like real watches. Violation of their work can cause a variety of diseases - from simple reduction of immunity to cardiovascular disease and obesity. Therefore, immediately adjust your internal clock and try not to neglect their rhythms!