Circadian Rhythm: The Body's Internal Clock

What is the Circadian Rhythm?

Every human has an internal biological clock, a mechanism that regulates a variety of bodily functions over an approximately 24-hour cycle. This natural process is called the circadian rhythm. It influences not only our sleep-wake cycle but also controls body temperature, hormone secretion, hunger, and metabolism. This rhythm allows our bodies to adapt to environmental changes, particularly the alternation of day and night.

How Does Our Biological Clock Work?

The circadian clock does not work alone; it is influenced by external and internal signals.

The Conductor: The Suprachiasmatic Nucleus

The body's master clock is a tiny region of the brain located in the hypothalamus, called the suprachiasmatic nucleus (SCN). The SCN receives information from the environment, including light, and sends signals to other parts of the body to synchronize their internal clocks.

Light Signals

Light is the primary cue that sets our internal clock. Specialized cells in our eyes' retinas detect light and transmit this information to the SCN. When sunlight is present, the SCN inhibits the production of melatonin. When light decreases, the SCN allows for the production of this hormone, which promotes sleepiness.

Melatonin, the Sleep Hormone

Melatonin is often called the sleep hormone. Its production is a key function of the circadian rhythm. The SCN stimulates its release by the pineal gland when darkness sets in, signaling to the body that it's time to prepare for sleep. Melatonin levels decrease as morning approaches and light appears.

The Impact on Health and Well-being

A well-synchronized circadian rhythm is essential for health. Disruptions to this rhythm can have significant negative consequences.

The Consequences of a Disrupted Rhythm

Disrupting our internal clock, for example through night shifts, jet lag, or excessive exposure to blue light from screens at night, can lead to sleep problems, mood disorders, weight gain, and an increased risk of chronic diseases.

How to Synchronize Your Circadian Rhythm

To maintain a healthy rhythm, it is recommended to expose yourself to natural light in the morning to wake up the brain, avoid bright lights and blue light from screens before bed, and stick to a regular sleep and wake schedule, even on weekends. These habits help maintain the proper functioning of our internal clock.