Which statement about the SCN is true?

Which statement about the SCN is true?

• A. It is located in the hypothalamus just above the optic chiasm
• B. It is located in the brainstem
• C. It is part of the cerebellum
• D. It is a gland in the endocrine system

Answer: (A)

The key idea is that the suprachiasmatic nucleus is the brain’s master clock, sitting in the hypothalamus just above the optic chiasm. This positioning lets it receive direct light information from the retina via the retinohypothalamic pathway, so it can synchronize daily rhythms to the day–night cycle. It isn’t located in the brainstem, nor is it part of the cerebellum, and it isn’t a gland; rather, it’s neural tissue in the hypothalamus that coordinates circadian timing and signals to other parts of the brain and body (including pathways that influence melatonin release by the pineal gland).

The key idea is that the suprachiasmatic nucleus is the brain’s master clock, sitting in the hypothalamus just above the optic chiasm. This positioning lets it receive direct light information from the retina via the retinohypothalamic pathway, so it can synchronize daily rhythms to the day–night cycle. It isn’t located in the brainstem, nor is it part of the cerebellum, and it isn’t a gland; rather, it’s neural tissue in the hypothalamus that coordinates circadian timing and signals to other parts of the brain and body (including pathways that influence melatonin release by the pineal gland).