tsirkadiaansete

Tsirkadiaansete, also known as circadian rhythms, are biological processes that display an endogenous, entrainable oscillation of about 24 hours. These rhythms are present in nearly all living organisms, including humans, and regulate various physiological functions such as sleep-wake cycles, hormone release, and cell regeneration.

The term "circadian" originates from the Latin words *circa* (meaning "around") and *dies* (meaning "day"). The rhythms are endogenous, meaning they are generated internally by the organism rather than being driven solely by external cues. However, they are also entrainable, meaning they can be synchronized to environmental cycles, particularly the 24-hour light-dark cycle.

In humans, the primary circadian rhythm is governed by the suprachiasmatic nucleus (SCN), a cluster of neurons located in the hypothalamus of the brain. The SCN receives light information from the retina and adjusts the timing of circadian rhythms accordingly. Disruptions to this system, such as those caused by shift work, jet lag, or sleep disorders, can lead to various health issues, including insomnia, mood disorders, and metabolic problems.

Circadian rhythms influence a wide range of biological processes, including:

- Sleep-wake cycles, where the body prepares for sleep during the night and wakefulness during the day.

- Hormone secretion, such as cortisol, which follows a daily rhythm and is highest in the early morning.

- Body temperature regulation, which typically peaks in the late afternoon and is lowest during early morning hours.

- Digestive processes, including hunger and metabolism, which are influenced by meal timing and light exposure.

Maintaining a consistent sleep-wake schedule, exposure to natural light during the day, and avoiding excessive light at night can help support healthy circadian rhythms. Understanding and respecting these natural cycles can improve overall well-being and reduce the risk of circadian-related disorders.