What makes us feel sleepy and what happens if we don't sleep?

Human life is actually very short, and the best years are fleeting. However, what makes us upset is that a small half of this short life is taken up by sleep.

Of course, sleeping is not just for humans. Almost all animals need to sleep. So have you ever wondered why animals need to sleep? On the surface, sleeping is because the body feels sleepy, but where does the sleepy feeling come from? What makes us feel sleepy? There is a saying that people only work for genes. Genes are the main body of life. Everything people do is for the inheritance of genes. This saying does make sense, so the reason for sleeping should be found from the genetic perspective. Scientists have been studying the issue of sleep for many years. The latest research has found that sleep may be closely related to DNA repair.

Genes exist in our bodies in the form of DNA. To put it simply, a DNA fragment that has a genetic effect is a gene.

DNA is a very complex substance, which is composed of more than 3 billion bases, and these bases can be divided into four types, namely adenine, guanine, cytosine and thymine. The order of these bases can produce countless genetic codes, so there are no two exactly the same people in the world, and there are no two exactly the same organisms. These codes composed of bases determine our physical features, body functions and whether we are prone to certain diseases. In our body, from skin to internal organs, cells everywhere are dying at any time, so new cells must be replaced, and the generation of new cells depends on the transcription and replication of DNA.

DNA will break during the replication process, but there is no need to worry because such breaks occur all the time.

Although DNA breaks happen all the time, they are not without reason. Under normal circumstances, DNA breaks are caused by harmful substances produced by the metabolism of body cells, but sometimes, we are exposed to harmful chemicals or infected with viruses, which can also cause DNA breaks. The most terrible thing is radiation damage. Excessive radiation can cause a large number of breaks in human DNA, so that cells cannot be regenerated, leading to death. Except for this extreme case, our body can repair normal DNA breaks by itself, just like DNA breaks, breaks happen all the time, and repairs are also ongoing all the time.

Although DNA repair is ongoing all the time, it can be fast or slow.

When we are awake, the repair rate of DNA is very slow, and after we fall asleep, the repair of DNA begins to accelerate, so the essential reason for sleeping is to allow DNA to be repaired better. Studies have found that the longer an animal is awake, the more DNA damage accumulates. When the DNA damage accumulates to a certain level, a protein in the body called PARP1 will send a signal to the brain, and then we will feel sleepy. The researchers conducted experiments using zebrafish. If the PARP1 protein in zebrafish is inhibited, the zebrafish will not go to sleep. Now we understand that animals cannot not sleep, not only because DNA cannot enter the rapid repair stage after sleep, but also because DNA repair during wakefulness is affected.

How is DNA repaired?

There are many ways to repair DNA, and the most important one is called "excision repair." As the name implies, excision repair is to remove the broken DNA fragments and then fill the blank part with newly synthesized DNA. Studies have found that melatonin can increase the activity of genes related to excision repair. If people do not go to bed, or stay up late and lack sleep, it will affect the secretion of melatonin, thereby reducing the ability to repair DNA. So, what happens if DNA is not repaired in time? DNA is related to the regeneration of body cells. A large amount of broken DNA will lead to changes in genetic information, thereby inducing a variety of malignant diseases. This is why staying up late is harmful to the body.

Since sleeping is for DNA repair, then the larger the animal, the longer it should need to sleep, right?

Interestingly, the actual situation is just the opposite. The size of animals is basically inversely proportional to their sleep time. The larger the animal, the shorter the sleep time. For example, elephants only need to sleep three or four hours a day to meet the needs of DNA repair, while mice need to sleep for 15 hours. Humans are of moderate size, and the best sleep time is about 7 hours a day. Why is this the case? What determines our sleep time? This question is still a mystery. Now we only know that sleep time is related to the circadian rhythm of organisms. As for how the circadian rhythm is formed, further research is needed. Now we only know that this circadian rhythm will be written into the genes of organisms and passed down from generation to generation.

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