5 facts about the biological clock
How to regulate sleep and wake cycles and why sleep gets worse with age
Circadian or circadian rhythms are cyclic fluctuations in the intensity of various biological processes associated with the change of day and night. This is a very important mechanism that prepares the body for changes in the environment. We tell you what you need to know about biological clocks and how to "tune" them.
Circadian rhythms are the most important in the body
Biorhythms help living beings to implement their genetic program most effectively: to look for food in suitable conditions, to restore strength in time, to prepare for weather changes. Life is permeated with biorhythms: both short–period (ultradian) - among them breathing and heartbeat, and long-period or infradian, which control hibernation in animals, bird migration and menstrual cycles in women. Circadian rhythms are timed to the rotation of the Earth, the change of light and dark hours, and are responsible for many aspects of our lives. We go to bed and get up at the same time, our memory can work better at certain hours, at some time of the day we cope with physical activity more easily. For example, our level of attention reaches its lowest point in the early morning. It is no coincidence that at 4 o'clock in the morning there are disproportionately many accidents – even taking into account driver fatigue and traffic intensity. During the night shift, major disasters occurred, such as Chernobyl and the Exxon Valdez tanker accident. Therefore, staying up until early in the morning is completely ineffective, even if the work is very important and urgent.
Circadian rhythms are characteristic of almost all forms of life
Even unicellular and bacteria have internal clocks. The period of circadian rhythms is usually close to 24 hours. The body is able to receive information about the change of day and night even in the absence of external stimuli and adapt to it. Chronobiology, a discipline that studies biological rhythms, was born through observations of plant life. In 1729, the French biologist Jean-Jacques de Meran noticed that the Mimosa pudica heliotrope plant closes its leaves at night and opens in the morning, even being in a dark basement and not receiving information about lighting. At the same time, the body needs to receive information from the outside so that the internal clock coincides with environmental conditions. Living creatures react to various parameters: humans are sensitive to the amount of light, while reptiles are guided by temperature changes. Circadian rhythms can be used to adjust other biorhythms. By daily changes in the amount of darkness and light, the body can very accurately determine the time of year. Some animals use this data as a signal to prepare for hibernation, and some – as a signal for mating, so that the cub is born in a warmer season and does not lack food.
Blind people receive information about changes in the time of day
There is a mechanism for controlling biorhythms in every cell – however, they all obey the suprachiasmatic nucleus. This area of the brain is located in the hypothalamus and controls the rhythm of the whole body. It receives information about the level of light and according to it rebuilds the work of its neurons. Some neurons of the nucleus are active during the day, some are active at night, and depending on this, they send signals to the centers of sleep or wakefulness, which, in turn, send signals to the rest of the body. The mismatch of the internal rhythm with the rhythm that is set by the light mode is called jetlag. If we abruptly change the time zone when flying a long distance – for example, we arrive during the day, while it's night in our city, we feel uncomfortable, because our body is set up for sleep, and the light conditions do not coincide with its parameters.
A blind person, from the point of view of a biological clock, can record a change in the time of day. The human eye contains a special set of light–sensitive cells called "photosensitive retinal ganglion cells" - it was found that in blind people and those who have light-sensitive cones and rods damaged due to a genetic disease, these cells can work normally.
The chronotype is partly determined by genes
There are several "clock" genes that are responsible for the production of certain proteins. Changes in the concentrations of these proteins determine the charge of cell membranes, which allows neurons of the suprachiasmatic nuclei of the hypothalamus to create electrical impulses at certain intervals, and as a result synchronize the functions of the body with the time of day. Due to strictly cyclic fluctuations in the biosynthesis of proteins PER1, PER2, PER3, CLOCK and BMAL1, our clocks have high accuracy.
The chronotype of a person, that is, "owl" or "lark", depends on genes by 54%. This does not mean that there is a gene that makes it necessarily an owl and a lark - there is just a certain combination of genes that is more common in some and less common in others. Another important factor is the social – that is, the daily routine adopted in society. The time at which a person has to get up for work or school and go to bed determines the 43% probability that he will go to bed and get up on time. The remaining 3% are due to age: in youth you can be an owl, and after 20 years you can gradually turn into a lark.
Sleep and wake cycles can be adjusted
Human sleep is affected by two factors – sunlight and the production of the hormone melatonin in the epiphysis. The greater the intensity of sunlight, the more active our internal clock is. If it is difficult for a person to wake up in the morning, it is recommended that he spend as much time in the sun as possible – even on a cloudy day, light breaks through the clouds, and this amount is enough to affect the centers of sleep and wakefulness. Any bright light source affects our internal clock: turning on the lamp at night, sitting at the computer before going to bed suppress the secretion of melatonin. Using gadgets before going to bed reduces melatonin production by 20% – so if a person has problems falling asleep, he should not spend a lot of time at the "blue screen". Even the light of a street lamp coming through the curtains can negatively affect health. Therefore, it is better to hang blackout curtains or blinds in the bedroom.
On the other hand, it is possible to regulate sleep with the help of melatonin. In an adult healthy person, it is produced at 21-22 hours, signaling that it is dark – then the brain switches to "night mode", slowing down the work of the whole body. With age, the amount of melatonin decreases – this is due to age-related degeneration of the pineal gland, which loses the ability to produce this hormone. To restore sleep and wakefulness cycles, elderly people have to take melatonin from the outside.
In addition, the cycles of sleep and wakefulness are affected by sports: if you exercise late in the evening, the period of sleep and wakefulness shifts forward, that is, a person falls asleep and wakes up later. If you exercise two hours before bedtime, before the evening melatonin production begins, the cycle will shift to an earlier time, and it will be much easier to fall asleep.
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