Circadian rhythms are the “clocks” of our internal mechanism that determine the phases of our cellular and organ activity over a 24-hour period. The word circadian means “about a day.”
Circadian rhythms affect body temperature, organ function, secretion of hormones such as cortisol (the primary stress hormone), and sleep. Each rhythm affects the others. In an environment with no time cues (such as light, clocks, calendars) our body clock completes a cycle that is slightly longer than the natural day — about 24 hours and 42 minutes, rather than exactly 24 hours. body temperature and sleep. Our body’s circadian rhythms dictate the rise and fall of our internal temperature over the course of a day. We are most likely to fall asleep when our body temperature is in the downward phase.