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Many people have this experience: they have to get up early in the morning to catch a plane or something important, set an alarm clock in advance, and wake up naturally before the alarm goes off, and it is only a minute or two earlier than expected.

(photo source: network screenshot) some people will attribute the reason to the biological clock. Yes, if you are a regular and healthy person, you do wake up at about the same time every day, which may vary slightly from season to season, but it is generally stable.

The biological clock is affected by factors such as light time, caffeine, diet and exercise, and adjusts our life rhythm in a very delicate and complex process, which greatly affects the time to go to bed and get up.

Biological clock is a periodic physiological, psychological and behavioral changes, not only human beings, many animals, plants and microorganisms have biological clock, different species of biological clock cycle is different, between 20 and 28 hours.

(photo source: Giphy) most of them change with the rise and fall of the sun. The most obvious example is that we work during the day and sleep at night, while cats usually sleep during the day and parkour at night.

Why is the biological clock so magical that it always wakes us up regularly?

In 2017, the Nobel Prize in Physiology or Medicine was awarded to three American biologists for their discovery of the control of circadian rhythms and molecular mechanisms. Through their research, they uncovered the secret of the biological clock rooted in genes.

Michael Young, one of the three heroes of the biological clock, is an American biologist and geneticist. By studying the sleep and awakening gene control patterns of Drosophila, he successfully isolated the key gene Period, referred to as PER gene. The mutation of this gene will change the original cycle pattern.

The protein encoded by PER gene is very important for maintaining cell circadian rhythm, and it is most obviously expressed in the suprachiasmatic nucleus (SCN) region of the brain, which is the main circadian rhythm regulator in mammals. The protein is constantly synthesized in the dark, while it is degraded in light.

The small green part of the picture is the suprachiasmatic nucleus (suprachiasmatic nucleus,SCN) (photo: wiki). After a whole day of degradation, PER protein decreases to a trough at night, your blood pressure drops, your heart rate slows down, it becomes difficult to think, and your body is urging you to go to bed. After a night of accumulation, PER protein levels reach a high level again before the bell rings the next day, so you can wake up refreshed.

After discovering the PER gene, Michael Young's team went on to explore new genes involved in the biological clock and discovered another gene called Timeless, or TIM. The mutation of TIM gene interferes with the mRNA cycle of PER gene expression. They found that even if there is no TIM gene, the protein encoded by PER gene can accumulate without degradation, but can not be moved to the nucleus, resulting in more effects.

PER1 protein (image source: AtikaAtikawa, wiki) so it seems that the biological clock must be influenced by both the PER gene and the TIM gene for the biological clock to work properly. Light also causes the proteins encoded by the TIM gene to fade quickly, causing circadian rhythms to change.

In short, we can see that the operation of the biological clock is closely related to light. And in good health, it maintains a relatively stable cycle so that you can wake up at about the same time every day.

But in some "superpower awakening events", even if people set the alarm clock to a time that they would not wake up at all, they would still wake up before the bell rang the next morning, which seems to be difficult to explain by the biological clock.

Some people in the scientific community have been studying this problem, but there is no final conclusion yet. Robert Stickgold, a professor of psychiatry at Harvard Medical School in the United States, who specializes in sleep and cognition, is also concerned about this interesting phenomenon, thinking that anxiety about being late may cause people to wake up early.

(photo Source: Giphy) there is a hypothalamic-pituitary-adrenal axis (HPA axis) in our bodies, which is an important part of the neuroendocrine system that regulates many physiological activities, such as the digestive and immune systems, and also affects our emotions. The HPA axis is a complex system for the human body to deal with stress, which is related to anxiety, bipolar disorder, insomnia and so on.

Sleep inhibits the activity of the HPA axis, especially during deep sleep, while activating the HPA axis in turn leads to insomnia or awakening.

In the HPA axis, the anterior pituitary secretes adrenocorticoid (ACTH), a polypeptide hormone. Before you wake up, the brain releases a lot of ACTH, which in turn signals the adrenal gland to release cortisol, the legendary "stress hormone", which wakes you up.

HPA axis and ACTH release process (photo: Pierrich Plusquellec, OA Evidence-Based Medicine) Jan Born, a professor in the Department of Medical Psychology and Neurobiology at the University of Tubingen in Germany, found in a group of experiments that people start secreting ACTH before the expected time, even if they get up earlier.

In this group of experiments, 15 subjects were invited, and their normal wake-up time was around 7: 00 in the morning. Bonn divided them into three groups. the first group was told in advance to get up at 6:00 the next morning, the second group was told to get up at 9:00 the next morning, and the third group was also told to get up at 9:00 the next morning. but in fact they will be woken up at 6:00.

Bonn found that there were significant differences in hormone levels among the three groups. People who get up at 6 a. M. are expected to have ACTH levels rising around 5 a. M., as if their bodies knew they were going to get up early today.

For those in the second and third groups who were completely relaxed and ready to sleep in the morning, Bonn did not monitor a rise in hormone levels an hour before they got up, whether they actually got up at 9 a.m. or were suddenly woken up at 6 a.m.

Although getting up at 9 a. M. was a little late for these people, which may have slightly affected the effectiveness of the experiment, Bonn did not observe whether subjects could wake up before the alarm went off, but the experiment at least showed that if we need to get up early, our bodies really respond in advance.

(photo Source: Giphy) other scientists also agree that anxiety about getting up can overwhelm the main biological clock to some extent, allowing us to wake up without an alarm clock in certain situations.

But there are still many unanswered questions about this system, such as how it works, how much impact it has on us, and so on.

(photo Source: Giphy) so how on earth did the body know it was almost time? I do have superpowers!

References:

[1] https://www.cdstm.cn/gallery/media/mkjx/qcyjswx_6683/202011/t20201127_1038091.html

[2] http://m.xinhuanet.com/he/2017-10/11/c_1121785136.htm

[3] https://en.wikipedia.org/wiki/Michael_W._Young

[4] https://en.wikipedia.org/wiki/PER1

[5] https://www.irishmirror.ie/lifestyle/health/scientificreasons-you-often-wake-up-24310147

[6] https://en.wikipedia.org/wiki/Michael_Rosbash

[7] https://www.npr.org/sections/health-shots/2022/12/26/1139781557/i-usually-wake-up-just-ahead-of-my-alarm-whats-up-with-that

[8] https://zh.wikipedia.org/wiki/%E4%B8%8B%E4%B8%98%E8%84%91%E2%80%94%E5%9E%82%E4%BD%93%E2%80%94%E8%82%BE%E4%B8%8A%E8%85%BA%E8%BD%B4

[9] https://www.ncbi.nlm.nih.gov/books/NBK279071/

This article is from the official Wechat account: bring Science Home (ID:steamforkids), author: everything.

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