Circadian rhythm

A biological cycle with a period of approximately 24 hours (from the Latin circa = about, dies = day). Circadian rhythms can be found in almost all life forms – animals and plants. Not only the essential functions of the entire organism but almost every individual organ and even every individual cell have their own genetically predefined circadian rhythm. The interplay of these individual cells and organs produces the outwardly visible or measurable circadian rhythms for the entire organism. Light is the most important “zeitgeber” for the circadian rhythm. It is the effect of light that synchronizes the rhythm to the 24 hours of a day.