The ______ movement is defined as the cycle that tells our bodies when to sleep, wake, and eat.

• A. Circadian Rhythm
• B. Metabolic Cycle
• C. Endocrine Cycle
• D. Ultradian Rhythm

Answer: (A)

Circadian rhythm is the body's roughly 24-hour cycle that regulates sleep, wakefulness, and eating. This internal clock, centered in the brain, uses light and darkness to stay synchronized with the day-night cycle. Light in the morning promotes wakefulness by reducing melatonin, while darkness increases melatonin and signals when it’s time to sleep. The rhythm also guides hormone release, body temperature, and appetite throughout the day, helping activities align with day and night. Other rhythms exist, like ultradian rhythms, which are shorter than a day and don’t govern the full daily pattern. So the cycle that tells our bodies when to sleep, wake, and eat is the circadian rhythm.