All animals on the earth have a physiological mechanism called "biological clock", that is, a 24-hour cycle rhythm from day to night, such as a light and dark cycle, which coincides with the earth's rotation once. The biological clock is controlled by the suprachiasmatic nucleus (SCN) of the hypothalamus. Like all mammals, SCN is located in the upper part of the oral cavity. Because of the biological clock, we have circadian rhythms of sleep, wakefulness and eating behavior.
The biological clock has four functions: prompting time, prompting events, maintaining state and forbidding.
Prompt time
It means that you must do something at a certain time. At this time, you will automatically think of it. For example, if you want to get up at 6 o'clock the next morning, you will get up automatically. In real life, most things are prompted by time, such as when to go to work, meet someone at a certain time, send flowers to your lover's birthday, April Fool's Day, catch the bus and so on.
Prompt event
It means that when you encounter one thing, the biological clock can automatically remind you of another. For example, if someone asks you to send something to A, when you meet A, the function of the biological clock will automatically come into play, so that you can immediately think of this entrusted thing. When you see something, "souvenir" (a kind of memory) most often comes to your mind. For example, when you see a panda, you will think it is a national treasure of China, it likes to eat bamboo, it is a symbol of friendship in China, and so on. For example, if you see a difficult problem, you will mobilize many memory blocks and solve it in the combination of some rules. This series of things must start with what you have learned in the past many years. This knowledge will not appear in your brain for no reason, but it can appear in your brain in turn under the action of biological clock.
Hold state
Refers to the power that people can persist in doing something when doing it. For example, eight hours of class is the result of the biological clock, and for example, people's eyes can concentrate when looking at something, which is also the result of the biological clock. When attention turns from vision to hearing, it is also the result of the function of reminding events. However, if you want to finish a class, you must use the function of biological clock to finish it, otherwise you will be sleepy or even skip class. This kind of maintenance can be continuous or intermittent. For example, the maintenance between you and your lover's family is intermittent, because you can't stay at home for a long time and do nothing. You have to go to work, tie a knot and get something.
Forbidden function
It means that a certain function or behavior of the body can be terminated by the biological clock. For example, when you see a terrible event (such as an earthquake), you may run away no matter what you are doing. This escape is the end of what you have done before. For example, you are concentrating on surfing the Internet and your father calls. Your biological clock is working when you stop surfing the internet. Without this function, one will never stop doing things, such as sleeping. Without this termination, this person will sleep for a long time and become a vegetable. The etiology of vegetative state may be related to the loss of control of this function.
Compared with these four functions, there are four corresponding centers in the human brain: time center, space center, function center and termination center.