Which process is linked to circadian rhythm and wakefulness drive?

• A. Process S
• B. Process C
• C. Melatonin
• D. Cortisol

Answer: (B)

Circadian rhythm and wakefulness drive are governed by the circadian process—the internal clock component of sleep regulation. This process, anchored by the brain’s circadian pacemaker in the suprachiasmatic nucleus, runs on roughly a 24-hour cycle and is synchronized to light. It modulates alertness across the day, promoting wakefulness when it’s daytime and increasing sleep propensity at night. It works alongside the homeostatic process, which builds sleep pressure the longer you are awake and dissipates during sleep. Hormones like melatonin reflect the circadian phase and help promote sleep as night approaches, while cortisol has its own daily pattern but isn’t the primary circadian wakefulness driver. So, the circadian process is the component tied to circadian rhythm and waking drive.