The Relevance of "Biological Clocks" for Modern Humans: Chronotype in the Age of Artificial Light The concept of "biological clocks" has ceased to be a metaphor and has become a strict scientific concept in chronobiology — the science of the temporal organization of living systems. For modern humans living under conditions of round-the-clock access to light, information, and work, understanding and respecting their circadian rhythms is not just a matter of well-being but a question of long-term health, productivity, and psychological resilience. Scientific Foundations: From Genes to Hormones Biological clocks are a hierarchical system. Their central "rhythm driver" is located in the suprachiasmatic nucleus (SCN) of the hypothalamus of the brain. This cluster of about 20,000 neurons synchronizes the work of peripheral clocks, located in virtually every cell of the body. Molecular Mechanism. The basis lies in a transcriptional-translational feedback loop. Genes "clocks" (such as Clock and Bmal1) initiate the production of proteins that, upon accumulation, suppress their own activity. This cycle lasts about 24 hours. Synchronizer No. 1 — light. The SCN receives information about light directly from special light-sensitive cells of the retina that react to the blue part of the spectrum. In the morning, light suppresses the production of the hormone melatonin (a sleep signal) and stimulates the release of cortisol (a hormone of awakening and activity). Impact on Physiology. These clocks regulate not only sleep and wakefulness but also the peak secretion of hormones, peristalsis of the intestines, immune system function, body temperature, cognitive functions, and even cell division. The Main Challenge of Modernity: Desynchronization Civilization has created a powerful factor disrupting the functioning of biological clocks — artificial lighting, especially in the blue spectrum (gadget screens, LED lamps), and a flexible, often round-the-clock, work schedule. This has led t ... Read more