Simply put, your circadian rhythm is your body’s internal clock. Operating on a roughly 24-hour cycle, it governs our sleep-wake cycle and plays a large part in everything from hormone release to body temperature. Circadian rhythms are not exclusive to humans and are found in nearly every living creature, from nearly every animal and plant to various micro organisms. Our circadian rhythms are regulated by a cluster of nerve cells in the hypothalamus known as the suprachiasmatic nucleus. This “master clock” of cells responds to, among other cues, light and, depending on how much is received, triggers such sleep-centric events as the release of melatonin.
When your circadian rhythm is disrupted, the immediate repercussions are that your sleeping, waking and digestive systems are thrown off; for lack of a better phrase you’ll, well, feel like crap. Longer-term effects include increased risk of cardiovascular events, obesity and, possibly, neurological problems like depression and bipolar disorder.
Are everyone’s rhythms the same?
Almost, but not quite. There are fluctuations in levels of alertness that everyone experiences (and can commiserate about) throughout the day—like that post-lunch slump that normally appears between 1:00 and 3:00 p.m. At night, our master biological clock makes us all sleepiest between 2:00 and 4:00 a.m. However, those ebbs and flows—including how intensely we crash in the afternoon—can vary by person. This accounts for some of us being “larks” and others “night owls,” despite the fact that we’re all diurnal creatures–active in daylight and asleep at night.