In sleep regulation, which brain region coordinates responses to light-dark cues and communicates with the pineal gland?

In sleep regulation, which brain region coordinates responses to light-dark cues and communicates with the pineal gland?

• A. Hypothalamus
• B. Suprachiasmatic nucleus
• C. Pineal gland
• D. Amygdala

Answer: (B)

Light-dark information is detected by retinal cells that contain melanopsin and send signals to the brain’s master clock, the suprachiasmatic nucleus in the hypothalamus. The SCN uses this input to keep the body's internal rhythms in sync with day and night. It then communicates with the pineal gland through autonomic pathways to regulate melatonin production: melatonin rises at night to promote sleep and falls during the day to help you wake up. The other regions aren’t responsible for coordinating light-dark signals with the pineal gland—the pineal gland itself makes melatonin, and the amygdala is mainly involved in emotion, not circadian timing.

Light-dark information is detected by retinal cells that contain melanopsin and send signals to the brain’s master clock, the suprachiasmatic nucleus in the hypothalamus. The SCN uses this input to keep the body's internal rhythms in sync with day and night. It then communicates with the pineal gland through autonomic pathways to regulate melatonin production: melatonin rises at night to promote sleep and falls during the day to help you wake up. The other regions aren’t responsible for coordinating light-dark signals with the pineal gland—the pineal gland itself makes melatonin, and the amygdala is mainly involved in emotion, not circadian timing.