Circadian rhythms regulate which daily cycle?

Circadian rhythms regulate which daily cycle?

• A. Digestive cycle
• B. Sleep-wake cycle
• C. Breathing cycle
• D. Circulation cycle

Answer: (B)

Circadian rhythms are the body’s 24-hour timing system that best governs when we feel awake and when we feel sleepy, aligning our behavior with day and night. The primary daily pattern they regulate is the sleep-wake cycle. The brain’s master clock in the hypothalamus is reset by light cues from the eyes, which shifts melatonin production to promote sleep at night and wakefulness during the day. Digestion, breathing, and circulation do show daily fluctuations too, but these are driven more by meals, metabolic needs, and autonomic control rather than being defined by the circadian clock as the main daily rhythm.

Circadian rhythms are the body’s 24-hour timing system that best governs when we feel awake and when we feel sleepy, aligning our behavior with day and night. The primary daily pattern they regulate is the sleep-wake cycle. The brain’s master clock in the hypothalamus is reset by light cues from the eyes, which shifts melatonin production to promote sleep at night and wakefulness during the day. Digestion, breathing, and circulation do show daily fluctuations too, but these are driven more by meals, metabolic needs, and autonomic control rather than being defined by the circadian clock as the main daily rhythm.