On the television show “24” a silent countdown usually means a character has died. But for some cells in the brain’s time-keeping center, silent running is part of life.
Cells in the suprachiasmatic nuclei, a tiny group of neurons in the hypothalamus, serve as a master clock to regulate the body’s circadian rhythms — daily fluctuations in hormone release, body temperature, blood pressure and other processes — and help set meal and bed times.
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