Circadian rhythms are natural, roughly 24-hour cycles that regulate various physiological processes in living organisms, including humans, animals, plants, fungi, and even microorganisms. The term "circadian" comes from the Latin "circa diem," meaning "about a day". These rhythms influence physical, mental, and behavioral changes, most notably the sleep-wake cycle, but also hormone release, appetite, digestion, and body temperature.
The master clock that coordinates these rhythms in humans is the suprachiasmatic nucleus (SCN), a group of nerve cells in the hypothalamus of the brain. The SCN responds to light and darkness, signaling the rest of the body to adjust accordingly. Light is the most important environmental cue, but other factors like food intake, stress, physical activity, and social interactions also play a role. When circadian rhythms are disrupted due to shift work, jet lag, or irregular schedules, it can lead to sleep disorders, and increase the risk of obesity, diabetes, mood disorders, heart problems, and cancer. Maintaining a consistent sleep schedule, managing light exposure, and a regular daily routine can support a healthy circadian rhythm.
