Circadian rhythms are the product of biological clocks, an evolutionary adaptation in response to the earth’s twenty-four-hour rotation period. They allow our bodies and minds to predict what will come next, so as to be better prepared for different situations and circumstances. For example, predicting when the sun will rise allows the brain to release wake-up chemicals (such as orexin, dopamine, and norepinephrine) and to suppress the drowsiness chemicals (such as melatonin, adenosine, and GABA) that might make us want to roll over and go back to sleep. The inner clock lets us wake up in the
...more
