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Zeitgeber

Meaning

A Zeitgeber, a German term literally meaning “time-giver,” is an external environmental cue that synchronizes an organism’s internal biological clock, or circadian rhythm, to the 24-hour cycle of the earth. The most potent and well-studied Zeitgeber is light, particularly sunlight exposure, which resets the master clock in the suprachiasmatic nucleus (SCN) of the hypothalamus. Other influential Zeitgebers include meal timing, physical activity, and social interactions. Consistent exposure to stable Zeitgebers is essential for maintaining a robust and healthy circadian rhythm, which in turn governs the precise timing of hormone release, including cortisol and melatonin.