Have you ever been able to observe the following phenomenon? The alarm clock is set in the morning – after all, you can’t miss the plane or the important meeting the next day under any circumstances. But even before the alarm sounds, your eyes are open. How can this be? There is a scientific reason for this phenomenon.
It has something to do with our sleep-wake rhythm. Since the beginning of time, this has helped humans to survive. During darkness, when our eyesight diminishes, and the environment becomes more dangerous, we retreat to a safe place. In the past, this was caves, but today it is usually a comfortable bed. Our body then uses time without light for regenerative processes – in other words, we sleep. And to ensure that this works smoothly, humans have developed several “internal clocks” that tick in unison with the external light-dark rhythm.
Every organ has its clock
These “internal clocks,” therefore, play an essential role in falling asleep and waking up. To put it simply, each organ has its clock. The pancreas, for example, adjusts its insulin production to the time of day. The clocks in adipose tissue regulate the storage and breakdown of fats.
The “master clock,” however, is located in the brain: the nucleus suprachiasmaticus. This is responsible for the rhythmic course of bodily functions and is in close consultation with the other “internal clocks” in the body. If we now wake up by ourselves before the alarm clock rings, we owe this to synchronizing all our body clocks.
Cortisol prepares us for getting up
The hormone melatonin and the messenger substance cortisol play a unique role in this process. While in the evening, the hormone melatonin increases more and more in the body to make us sleepy and prepare us for the night’s rest; from about halfway through sleep, the production of cortisol is ramped up.
The stress hormone releases energy reserves, activates the metabolism, and increases blood sugar levels and protein turnover, thus preparing us for getting up. And sometimes, it prepares us so well that we wake up before our external signal – the alarm clock. Scientific studies even prove this.
“Inner clock” is also controlled unconsciously.
Studies by neuroscientist Jan Born from the University Hospital of Tübingen have shown that cortisol secretion increases rapidly in the hour before waking up. In the sleep experiment, the participants were told they would be awakened at six o’clock sharp the following morning.
And indeed, that night, the cortisol level jumped punctually one hour before the time of the alarm clock. However, if the test subjects were not prepared for this, the hormone surge did not occur. What does this mean? Cortisol is therefore not only controlled by the body clock but also unconsciously: for example, when we know that “tomorrow I have to get up at half past five. Reasonably practical if the alarm clock fails!
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