biological clock
Quick Summary
A biological clock is an internal timing mechanism within living systems that explains the timing of behaviors and physiological processes. This internal clock is closely related to the circadian rhythm, which refers to the approximately 24-hour cycle of biological activity in humans.12
The circadian rhythm is regulated by the brain's hypothalamus, specifically the suprachiasmatic nucleus (SCN). The SCN receives light and dark signals from the retina and influences the pineal gland to produce melatonin. Melatonin production increases in darkness, promoting sleep, and decreases in light, promoting wakefulness. Disruptions to this cycle, such as from transmeridian travel, can cause jet lag.234
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