Which controls wakefulness, alertness, and sleepiness states?

• A. Thalamus
• B. Pons
• C. Hypothalamus
• D. Cerebellum

Answer: (B)

Wakefulness and alertness are controlled by the reticular activating system, a network in the brainstem that keeps the cortex alert by sending activating signals. This system travels through the brainstem, including the pons, and connects with the thalamus and cortex to regulate arousal and sleep–wake transitions. Because the origin of this arousal signal lies in the brainstem, the pons is the best choice for controlling these states. The thalamus helps relay and modulate information once arousal signals reach the cortex, the hypothalamus governs circadian rhythms and hormonal signals that influence sleep-wake cycles, and the cerebellum focuses on movement coordination rather than arousal.