[单选题]
The graph shows the circ
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Which statement correctly describes the event responsible for the change in the rhythm of body temperature after exposure to light?
A. The secretion of melatonin from the thyroid gland was elevated by light exposure.
B. The secretion of melatonin from the pineal gland was suppressed by light exposure.
C. The secretion of thyroxin from the thyroid gland was elevated by light exposure.
D. The secretion of thyroxin from the pineal gland was suppressed by light exposure.
参考答案:
B
本题详细解析:
Explanation:
The graph shows the time of day on the horizontal axis and body temperature on the vertical axis. The black line indicates the body temperature rhythm of an individual following their normal light-dark cycle, and the dashed line indicates the body temperature rhythm of that same individual after exposure to a pulse of 1000-lux light at their typical bedtime. The body temperature rhythm after exposure to light has the same shape as that before exposure, but the peak of this rhythm is shifted later in the day relative to the individual’s typical body temperature.
The hormone melatonin regulates an individual’s circadian rhythm and sleep-wake cycle. Melatonin is released by the pineal gland, not the thyroid gland (Choice A), at night to control circadian cycles. If the circadian cycle is shifted to later in the day, it is likely that the exposure to light suppressed the release of melatonin from the pineal gland.
Thyroxin is secreted by the thyroid gland, not the pineal gland (Choice D) and regulates metabolic rate and body temperature, not the sleep cycle (Choice C).
