How is circadian rhythm regulated?
Circadian rhythm coordinates roughly 24-hour biological processes through cellular clocks and environmental cues.
Biological mechanism and regulation
Clock genes form feedback loops, and the brain's suprachiasmatic nucleus uses light from the eyes to coordinate body clocks.
Evidence, applications and limits
Night light, shift work and time-zone changes can cause misalignment. Melatonin signals darkness but is not the sole explanation for sleep. No single molecule or measurement explains the whole system; cell type, timing, environment and feedback must be considered together.
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