As you have heard, in 2017, the Nobel Prize in medicine or physiology went to the Americans Jeffrey C Hall, Michael Rosbash, Michael W Young for their discoveries in the field of circadian rhythm - the mechanism of cells that regulates the internal clock people, animals and plants.
Scientists, for example, managed to isolate a gene that regulates the circadian rhythm of the Drosophila fly.
The internal clock is responsible for sleep cycles, blood pressure, hormone levels, and body temperature. They affect all life on earth, from unicellular cyanobacteria to higher vertebrates, including us humans.
The sun and other Zeitgebers
The study of internal clocks has become a completely independent branch of science, which is called chronobiology.
Chronobiology, as the name suggests, boils down to the study of biological rhythms and how they relate to the environment: the Germans call them Zeitgebers, that is, synchronizers.
The most obvious Zeitgeber, of course, is sunlight and its cycles.
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We humans, from time immemorial, have observed the reactions of nature to the increase and decrease of sunlight, primarily the way plants open and close their flowers and leaves in accordance with the amount of light received.
But only in the 18th century did a person manage to prove that it was not only about external signals: something inside the organism itself reveals the secret of the biological clock, which depends not only on how high the sun rose in the sky.
Up, mimosa
One of the first to make scientific observations of this phenomenon was the French astronomer Jean Jacques d'Ortous de Mairan.
It was 1729 in the yard when he placed a mimosa bush in the darkness and noticed that it still opens and closes its leaves, depending on the time of day and whether the sun shines somewhere, which was not nearby.
Mimosa in the sun / flickr.com, Ben Blash
From this, he concluded that the plant's impulse to open and close the leaves is related to an internal mechanism rather than a consequence of a slavish reaction to external stimuli in the form of changes in sunlight.
But it is clear that if daylight fluctuations are removed from the equation for a longer period of time, the biological clock, of course, will go wrong sooner or later.
Insulation underground
One of the first scientists who in our time actively studied the influence of the biological clock on humans was the French geologist and speleologist Michel Siffre in the early 60s.
This was at the beginning of the era of space travel and during the Cold War, when a person became interested in the body's reaction to long periods of isolation, for example, in a space capsule or in a bomb shelter after an atomic war.
In 1962, 23-year-old Sifr made a breakthrough with a bold experiment in which he was able to prove that we have a built-in clock, just like plants do.
He isolated himself from the world from July 18 to September 14, 1962 in the Scarasson Glacier Cave, which is located in the French Alps at a depth of 100 meters underground.
Sifr maintained contact with the outside world only through the telephone line, which he used to report when he went to bed and when he got up.
Severe disorientation
The absence of external stimuli and clocks, over time, completely disorientated Sifr in terms of the passage of time (and, as he later admitted himself, almost drove him crazy).
Sifr himself believed that he slept in cycles of 15 hours and that he had completely lost touch with the natural circadian rhythm. But it turned out that his body perfectly kept track of time, living for days on average 24.5 hours long.
After Sifr spent 63 days in an ice cave, he finally came out into the light of day, believing that it was August 20 on the calendar. In other words, he lost a whole month in his mind.
But the body knew better. And Sifr was able to prove once and for all that we, humans, are equipped with biological clocks.
More and more scientists are delving into this topic
A couple of years later, Michel Sifre conducted another similar experiment, but this time as an observer for two other cavers, Josie Laures and Antoine Senni. They, too, allowed themselves to be isolated underground, each in their own cave, about a hundred meters apart.
The only people on the surface of the earth with whom Lores and Senny kept in contact by phone were scientists recording their sleep times, physical indicators and meals.
Lores and Senny did not have to suffer from idleness, the purpose of the experiment was not to completely deprive them of sensory stimuli, they were allowed to, say, listen to music or do some manual work: for example, Lores knitted.
Lores spent 88 days in her cave, while Senny spent 126 days in hers. When they finally emerged from there, both were in relatively good physical condition, but even more confused than Sifr after the experiment.
Antoine Senny believed, for example, that he left the cave on February 4, when the correct date was April 5. Josie Lores was generally in good physical condition, but it took a very long time to restore the natural sleep cycle.
April 05, 1965. Antoine Senny (center) leaves the cave after 125 days alone. He is greeted by Josie Lores (right), another participant in the experiment who spent 88 days in isolation / AP Photo
At that time, isolation managed to deceive even the biological clock.
It turned out that Senny fell into such a rhythm in which he could sleep for 30 hours in a row, although he himself believed that he only lay down for a light nap.
The sleeping beauty of reality
More recent studies in isolation have shown that people can extend their sleep cycle by as much as 48 hours if they are not exposed to any external stimuli.
But also repeated experiments with isolation have shown that a person's internal clock, our circadian rhythm, naturally occurs in a cycle of just over 24 hours. But where is this clock, purely physically?
All this is associated with a small area in the brain - the suprachiasmatic nucleus of the hypothalamus. It is about the size of a grain of rice. In practice, it is this biological clock that regulates our daily rhythm.
And it gets basic time information from the sun. In the evenings, when the lights go out, it sends a signal to the pineal gland to start producing melatonin, which tells the body to go to bed.
In summer, this mechanism works the other way around, the level of melatonin decreases, as the amount of light increases, which, among other things, increases the production of prolactin in women, which increases fertility.
So everyone who was born in the region of the vernal equinox, perhaps, should thank the summer sun, which nine months earlier put dad and mom in the right mood.
Those who do not see
The suprachiasmatic nucleus, which regulates our internal clock, exits, receives a signal from the eyes, through vision. But what about blind people? How is their biological clock regulated?
In fact, blind people do often suffer from sleep problems and have to take melatonin to relieve symptoms.
But there is an American and British study that shows that even in a completely blind person who has destroyed the retinal visual cells themselves, that is, the so-called rods and cones, the eye can register light, including if the person himself does not know about it.
In other words, the signal can still enter the hypothalamus through the optic nerve. So your biological clock may be working even if you can't see. And although our internal clocks continue to function for long periods in isolation, without light we get sick.
Experiments with laboratory mice showed that mice that were placed in the dark for long periods of time suffered from symptoms similar to depression.
Lack of light reduces dopamine secretion, affects blood sugar levels and even impairs memory. Both in mice and in humans.
Deer Cunning
However, the reindeer that graze in the north in Lapland have handled it in a very clever way. After all, they live in continuous darkness, then in continuous light, depending on the season, so they had to be in constant stress.
But it turned out that the biological clock of deer works somewhat differently than ours. Our internal clock makes sure that melatonin is released in a relatively regular 24-hour cycle.
In deer, the production of melatonin is more directly related to the amount of light received, rather than to a genetically determined biological clock.
That is, the level of the hormone rises when it is dark, and decreases when it is light. In other words, deer have no diurnal rhythm, rather we can say that they have an annual rhythm.
This allows them to continue chewing on their lichens if they can find them, regardless of the time of day and without being distracted by the internal clock that says it's time to sleep.
And it looks like this is quite a working option for them. Think yourself, have you ever seen a deer with depression?
Marcus Rosenlund