'Clock' in Our Bodies 

Dad took Daniel to the museum to see the dinosaur exhibition on Sunday. Daniel was so excited that he wouldn't go to bed even if it's 8:30 in the evening. Mom came to Daniel's room and found that he was video chatting with his aunt. She joined them and then hung up a while after. Daniel climbed into bed and turned to Mom and said, "Mom, I can't sleep now. Can I stay up later?" Mom replied firmly, "No." Daniel said unhappily, "Adults are really overbearing. Force me to close eyes and pretend to sleep when I can't." Mom smiled and said, "I'm not overbearing. It's just because you have a 'clock' in your body. It means you have to go to bed at a certain time, or you'll be tired tomorrow."

"A clock? Where is it? Why can't I see it?" Daniel asked Mom curiously, laying on the bed.

"Precisely, it's biological clock, which is largely controlled by the suprachiasmatic nucleus on the hypothalamus of head. Open your mouth and touch your palate. It's almost right above where you touch. We all fell hungry when it's time to eat, and get sleepy at night when it's time to go to bed. The biological clock determines the sleep-wake cycle. If you don't sleep when it's time for bed, your biological clock will be like a messed up clock that needs to be adjusted to get back to normal. And children like you are still growing. Sleep time is the best time for growth, because your body will secrete exuberant growth hormones to help you grow tall in this period. It is only secreted at a certain period of time when you are asleep. If you miss this sleep opportunity, growth hormones will not be secreted"

"Oh-oh," Daniel lay back on the bed and listened to Mom.

"Is the biological clock vary from person to person?' Daniel asked confusingly.

"It's of course different from person to person. But most of them are similar. For example, people will be hungry at noon, and fell sleepy at 12 o'clock midnight. But there are some exceptions. For example, some people are like owls. They are more energetic at night and sleepy in the daytime. In some cases, it's a sign that the biological clock has been disrupted. But some people are just born that way and are more productive at night."

"Maybe I'm one of those night owls," Daniel answered as if he was talking in sleep.

"You are still a child. A regular routine is good for your health and physical growth."

"Why is it healthy to go to bed on time?" Daniel found himself feeling really sleepy.

"After all, humans have evolved over millions of years and are used to sleeping at night. Scientists have shown that when we fall asleep, our brains are able to discharge the waste produced during the daytime. This is important for our brain health. What's more, while we are sleeping, our brain can 'clean up' our memories, keeping the important ones and deleting others. In short, there are so many benefits of sleep."

Seeing Daniel couldn't open his sleepy eyes, Mom lowered her voice, turned off the lights and then quietly walked out of the room.

Author: Huang Jing