tsirkadiaanne

Tsirkadiaanne is a term used in chronobiology to describe the set of approximately 24-hour biological cycles that regulate a wide range of physiological and behavioral processes in living organisms. These rhythms are endogenous but are synchronized (entrained) by environmental cues such as light and temperature, allowing organisms to align their internal state with the day-night cycle.

The core mechanism of tsirkadiaanne involves molecular clocks that operate in nearly all cells, coordinated by a central pacemaker in the brain, the suprachiasmatic nucleus (SCN), in many animals. A network of clock genes and proteins engages in transcription-translation feedback loops, creating oscillations. Peripheral clocks in tissues like liver, heart, and muscle run in parallel, adjusted by signals from the SCN and by behavioral factors such as feeding.

Functions of tsirkadiaanne include regulation of the sleep-wake cycle, hormone release (for example melatonin and cortisol), body temperature, metabolism, and cognitive performance. In plants, circadian-like rhythms influence photosynthesis, growth, and flowering. Disruption of these rhythms can result from irregular light exposure, shift work, travel across time zones, or aging, and is associated with sleep disorders, metabolic issues, and mood disturbances.

Historically, observations of daily activity patterns led to formal study in chronobiology, with the term circadian derived from Latin circa diem, meaning about a day. Tsirkadiaanne research informs medicine, occupational health, and agriculture, highlighting the importance of aligning biological timing with environmental cycles for health and performance.