Circadian rhythms are natural, roughly 24-hour cycles that regulate various physical, mental, and behavioral changes in living organisms. These rhythms are controlled by a biological clock, a system of proteins encoded by genes that switch on and off in a specific order. A master clock, located in the brain's hypothalamus within the suprachiasmatic nucleus (SCN), coordinates all the biological clocks in an organism. The SCN receives light and dark signals from the eyes and, among other functions, controls the production of hormones like melatonin, which induces sleepiness.
External cues, such as light, food intake, stress, physical activity, and social environment, can influence circadian rhythms. Disruptions to these rhythms can result from shift work, jet lag, inconsistent sleep schedules, and even the use of electronic devices at night. Such disturbances have been linked to various health problems, including obesity, type 2 diabetes, high blood pressure, cardiovascular disease, and aggressive behavior. Maintaining a stable routine with consistent sleep-wake times and exposure to sunlight can help regulate circadian rhythms and promote better sleep and overall health. Recent research has also uncovered how circadian clocks within microscopic bacteria precisely control when different genes are activated and deactivated during the 24-hour cycle, which could have implications for understanding circadian rhythms in other organisms.
