Chronobiology (ancient Greek: χρόνος, chrónos 'time'; βίος, bíos 'life' and λόγος, lógos 'education') as a branch of biology investigates the temporal organization of physiological and biochemical processes and repetitive behavior patterns in living beings. The observable, recurring events are referred to as biological rhythms: they can be repeated with different periods of time and adapt internal states to external circumstances, both, as a reaction, but especially in anticipation.
One of the most important biological rhythms is the circadian (Latin: circa: 'about', dies: 'day') rhythm, which is driven by an internal clock and has a phase length of just about 24 hours. At the heart of this clock is a simple transcriptional/translational feedback loop (TTFL) made up of so-called clock genes and their protein products. This clock has to be adjusted a little bit every day by external cues, by so-called Zeitgeber, so that the clock arrives back at the starting point exactly after a 24-hour solar day. Sunlight is the most important Zeitgeber for adjusting the internal clock, also due to its high amount of blue light in the spectrum. But also temperature, melatonin (used to reduce jet lag, in blind people and in shift workers) and exercise are also important Zeitgeber for adjusting the circadian clock in our brain. If the internal clock is not synchronized by Zeitgeber - for example in blind people, under constant laboratory conditions, or in the far north with constant darkness in winter - many natural rhythms continue to oscillate unchanged and undiminished. However, the length of the period (τ) then corresponds only roughly to the 24-hour solar day (free-running rhythm).
In 2017, the scientists Jeffrey C. Hall, Michael Rosbash and Michael W. Young were awarded the Nobel Prize in Medicine for discovering the molecular mechanisms underlying the circadian rhythm of cells.
Coaches Corner #16 - Jörg Stehle