Circadian
Circadian Rhythms
Circadian rhythms are natural, internal processes that regulate the sleep-wake cycle and repeat roughly every 24 hours. These rhythms are driven by a circadian clock, and they have been widely observed in plants, animals, fungi, and cyanobacteria.
Overview[edit | edit source]
Circadian rhythms are endogenously generated, although they can be modulated by external cues such as sunlight and temperature. The term "circadian" comes from the Latin words "circa," meaning "around," and "diem," meaning "day," indicating that these rhythms are approximately one day in length.
Biological Mechanism[edit | edit source]
The primary circadian clock in mammals is located in the suprachiasmatic nucleus (SCN) of the hypothalamus. The SCN receives direct input from the eyes, allowing it to synchronize with the light-dark cycle of the environment. This synchronization is crucial for maintaining the alignment of the circadian rhythm with the external world.
Molecular Basis[edit | edit source]
At the molecular level, circadian rhythms are generated by a set of core clock genes and proteins that form feedback loops. These include the CLOCK and BMAL1 proteins, which activate the transcription of PER and CRY genes. The PER and CRY proteins then inhibit the activity of CLOCK and BMAL1, creating a self-regulating loop that oscillates with a period of about 24 hours.
Functions of Circadian Rhythms[edit | edit source]
Circadian rhythms influence various physiological processes, including:
- Sleep: The sleep-wake cycle is one of the most well-known circadian rhythms.
- Hormone secretion: Hormones such as cortisol and melatonin are released in a circadian pattern.
- Body temperature: Body temperature fluctuates throughout the day in a predictable pattern.
- Metabolism: Circadian rhythms affect metabolic processes and energy balance.
Circadian Disruption[edit | edit source]
Disruption of circadian rhythms can lead to various health issues, including sleep disorders, depression, obesity, and cardiovascular disease. Common causes of circadian disruption include shift work, jet lag, and exposure to artificial light at night.
Research and Applications[edit | edit source]
Research into circadian rhythms has led to the development of chronotherapy, which involves timing medical treatments to align with the body's natural rhythms to improve efficacy and reduce side effects.
Also see[edit | edit source]
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Contributors: Prab R. Tumpati, MD
