Coordinated by the SCN, light inhibits melatonin secretion during the dark cycle.

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Multiple Choice

Coordinated by the SCN, light inhibits melatonin secretion during the dark cycle.

Light input from the retina informs the SCN, the body’s master clock, about the time of day and schedules melatonin production by the pineal gland through a sympathetic pathway. In the presence of light, the SCN signals to suppress the enzyme (Aanat) that drives melatonin synthesis, so melatonin levels stay low. In darkness, that suppression is lifted and melatonin rises, promoting sleep. Therefore, light can inhibit melatonin secretion even during the dark cycle, making the statement true.

Light input from the retina informs the SCN, the body’s master clock, about the time of day and schedules melatonin production by the pineal gland through a sympathetic pathway. In the presence of light, the SCN signals to suppress the enzyme (Aanat) that drives melatonin synthesis, so melatonin levels stay low. In darkness, that suppression is lifted and melatonin rises, promoting sleep. Therefore, light can inhibit melatonin secretion even during the dark cycle, making the statement true.

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