The main “circadian clock” in mammals, which regulates the levels of certain chemicals in the body, is located almost in the very center of the brain. This area, consisting of more than 20,000 nerve cells, is called the suprachiasmatic nucleus (SCN). It is responsible for circadian rhythms. In accordance with incoming information about the light surrounding the body, this core gives commands to other parts of the brain to produce certain hormones and neuropeptides (proteins of the nervous system). So, when it gets dark (and not when the clock shows dark), the brain receives a signal through the retina that it’s time to sleep, and when it gets light, it’s time to get up. Therefore, waking up for work in the spring and summer is much more pleasant than trying to open your eyelids in the middle of winter. Each neuron of the suprachiasmatic nucleus has its own clock and operates at its own rhythm: the cluster of nerve cells here looks like a real society, where each cell has its own idea of life and an opinion about what time of day it is. But, as in real life, in order to achieve a certain positive result — coordinating the daily rhythms of the body’s activity and metabolism — they need to work together and coordinate their regime. These cells synchronize their sense of time with someone else’s using a special VIP protein. Thanks to this tiny peptide (it consists of only 28 amino acids) we get more active during the day and want to sleep closer to night. But everything should be in moderation: if there are too many VIP cells in the brain, the cells get out of the “temporary rut”, which greatly affects our well-being and mood. Interestingly, jet lag (jet lag syndrome) and short-term deprivation (sleep deprivation) have exactly the opposite effect on people suffering from mental disorders. Thus, in patients with depression and bipolar disorder, the chemical connections between the neurons of the suprachiasmatic nucleus are extremely weakened or completely absent. The VIP protein, which, as we remember, is necessary for the creation of these bonds, is photosensitive, which means that it is extremely actively produced during the light phase of the day. Therefore, by artificially increasing the length of the day through bright lighting and a “sleep ban”, we can stimulate the production of this protein in patients with depression, thus normalizing not only their circadian rhythms, but also their general mental state. This practice does not work on healthy people and excessive glow can only lead to dysfunction of the suprachiasmatic nucleus.

Humans are social and extremely active creatures, so sometimes the internal clock shifts relative to the external clock: we travel to other continents in other time zones or simply go to bed too late. All these movements, called jet lag, greatly spoil the “mode of operation” of our body. Experts say that even a seemingly harmless switch to daylight saving time increases the risk of fatal accidents and the number of heart attacks. It is also assumed that some historical disasters of the last century (the nuclear accident at Chernobyl and the explosion of the space shuttle Challenger) were associated precisely with lack of sleep and circadian rhythms in the employees of these installations!

Scientists advise listening to your body and taking into account its “circadian-circadian” opinion: do not stay up late at work or study, do not exercise at night, do not eat an hour before bedtime, but walk outside more during the day. And of course, turn off your computer and TV at least half an hour before bedtime. Numerous studies show that the glow from gadgets at night, which mimics daylight, destroys connections between neurons and has an extremely negative effect on human physiological and cognitive functions. Provide your suprachiasmatic core with an adequate light regime, and yourself with a healthy sleep and a cheerful day!