Read an Academic Passage

Understanding Our Internal Clocks

Nearly all living organisms, from bacteria to humans, possess an internal biological clock that governs their daily rhythms. Known as circadian rhythms, these are roughly 24-hour cycles that influence critical functions like the sleep-wake cycle, hormone release, body temperature, and metabolism. In humans, this internal timekeeper is controlled by a master clock located in a part of the brain called the suprachiasmatic nucleus (SCN). The SCN coordinates the body's various biological clocks, ensuring they are synchronized and functioning in harmony to regulate our physiological processes throughout the day and night.

While these rhythms are generated internally, they are adjusted or reset by external cues from the environment, known as zeitgebers, which is German for "time givers." The most powerful zeitgeber is light. When light enters the eyes, it sends signals to the SCN, which then aligns the body's clock with the day-night cycle. This is why exposure to light in the morning can help us feel awake, while darkness at night prompts the release of melatonin, a hormone that promotes sleep. Disruptions to this natural cycle, such as those caused by jet lag or shift work, can have detrimental effects on health.

Modern lifestyles present numerous challenges to maintaining healthy circadian rhythms. The widespread use of artificial lighting and electronic screens at night can confuse our internal clocks, suppressing melatonin production and making it harder to sleep. Chronic misalignment between our internal clock and our external environment has been linked to various health problems, including sleep disorders, obesity, and mood disorders. Consequently, researchers in the field of chronobiology are increasingly emphasizing the importance of a regular schedule and proper light exposure for overall well-being.