All living beings on our planet – humans, animals and plants – have an internal clock that tells them when it’s time to sleep and when they need to be active. But how is this internal clock controlled?
Back in the 18th century, scientists had discovered that plants have a biorhythm that causes them to close their leaves at dusk and reopen them the next morning. Even plants that were in complete darkness maintained this 12-hour rhythm. Nobody could explain the reason for that at the time.
How does a plant know that it is day?
In the 1970s, scientists around US biophysicist Seymour Benzer discovered that a gene is partly responsible for the organic rhythm of fruit flies. In the 1980s, this year’s Nobel Prize winners isolated this gene.
Hall and Rosbash, who worked together at Brandeis University, came across a protein that accumulates cells during the night and slowly breaks down during the day. “The protein inhibits its own production,” said Till Roenneberg, a chronobiologist at the Ludwig-Maximilians-Universität München, after the awards in the DW interview. “They showed that genes control our internal clock.”
The crucial protein
This mechanism applies not only to fruit flies, but also to humans and plants. They “know” that it has to be night, when much of the protein is present, and day, when the cells have mined the most. This natural cycle adjusts our bio-rhythm to the earth’s rotation.
In the relatively small and young research field of chronobiology, scientists deal with recurrent phenomena in living organisms. The discovery of the Nobel Prize winners in the 1980s gave research a boost.
How does the biological clock work?
Our internal clock lowers the blood pressure at night and makes the breath flatter. At the same time it gives the starting signal for the nightly repair and recovery programs. The absolute low reaches our power curve between 3 and 4 o’clock in the night. Towards morning, the body slowly switches back to activity. From 10 am to 12 noon and around 5 pm most people are most productive. By 14 o’clock, however, quite a few feel dull. The sun ensures that our internal timepiece is clocked from the outside. The sunlight gives the clock the calibration impulses from the outside.
“Today we know that the internal clock is a highly complex system,” says Roenneberg. “There is not just one clock in the brain, but one clock in every cell of our body.”
An example of our internal clock can be seen on the liver. During the day she builds up glycogen from glucose and in the evening she breaks it down to supply the body with glucose. “If construction and dismantling take place at the same time, that is pointless,” says Henrik Oster from the Institute of Neurobiology at the University of Lübeck , “there must be a temporal separation.”
When the internal clock gets out of tune, we feel weak and uncomfortable. If it does not harmonize with the “outer clock”, ie the actual time of day, we can even get sick.
The internal clock was “not necessary for survival, but important to coordinate metabolic processes and the daily rhythm,” explains Henrik Oster.
After a flight from Los Angeles to Frankfurt our inner clock follows. Lead fatigue and fatigue are the result. This normalizes again within a short time.
For shift workers, things are different. The persistent dissonance between internal and external clock has negative consequences such as a higher risk of developing mental illness, diabetes or cancer.
Late sleepers and early risers?
So whether we are late sleepers or early birds is also anchored in our genes. Anyone who lives against his inner clock and, for example, ignores his personal sleep-awake rhythm or his need for sleep, will sooner or later be punished by nature: with nervousness, insomnia, stomach problems or depression, or even heart disease.
“The internal clock has a knack for everything that happens in the body,” says Roenneberg. However, she is different for everyone. Of these night owls and larks can sing a song. Researchers studied skin cells of people who are early and those who prefer to get up later. They found that the inner clock is a bit faster for the early risers.