Chronobiology: Understand the internal clock

Each of us has an internal clock that controls our biorhythm and sleep-wake behavior. Here you can find out how the internal clock works and why it is so important for our health.

Table of contents

1. What is the internal clock?
2. Zeitgeber of the internal clock
3. What influence does the internal clock have?
4. What influence does the internal clock have on sleep?
5. Changes in the internal clock over the course of life
6. What happens when the internal clock is disturbed?
7. Conclusion

1. What is the internal clock?

The internal clock is the biological system that controls the timing of our body and adjusts it to a certain rhythm. It consists of a master clock, which synchronizes our 24-hour rhythm and many peripheral clocks located in the organs and tissues.

The master clock is located directly in our brain, more precisely in the suprachiasmatic nucleus (SCN), a part of the hypothalamus. It determines our sleep-wake rhythm, controls the peripheral clocks and determines the so-called circadian rhythm, to which almost all bodily processes adapt. This rhythm is already determined from birth by so-called clock genes in our cells and ensures that the body's functions are synchronized with the day-night rhythm.

The circadian rhythm is not exactly aligned to the 24-hour day, but actually lasts a little longer, namely about 24 hours and 11 minutes. In order to get closer to the natural 24-hour day-night rhythm, the internal clock system must therefore be regulated again and again. This is done with the help of the internal clocks and their so-called time givers. The most important and strongest time giver is light..

2. Zeitgeber of the internal clock

Light

Light is the most important and strongest timekeeper of the internal clocks. It is detected by special cells in our optic nerve, which send a signal to the suprachiasmatic nucleus in the brain. From there, numerous physiological processes are controlled, for example the release of certain neurotransmitters and hormones as well as numerous metabolic activities.

feeding times

Metabolism and nutrition are also closely linked to the internal clock. The time of food intake and the composition of food can have a direct influence on our internal clock. Correct meal timing can therefore also reduce the effects of jet lag when traveling across time zones.

Psychological factors (stress, worries)

Psychological stress, frequent brooding or persistent worries can also affect the internal rhythm, for example by delaying falling asleep.

Physical activity

Physical activity can also influence our internal clock through its direct influence on our metabolism and numerous physiological systems. Exercise in bright daylight can promote acute alertness, whereas higher intensity physical activity in the afternoon can increase sleep pressure and thus make it easier to fall asleep in the evening. Physical activity at the right time can therefore also help to improve internal rhythm and sleep.

3. What influence does the internal clock have?

The internal clock determines numerous body functions. It controls the body temperature, blood pressure, the release of hormones and neurotransmitters as well as metabolism and the sleep-wake rhythm.This can be seen, for example, in natural fluctuations during the day and night.

This allows the body to process food better at certain times or to compensate for blood sugar fluctuations more easily. Before newborns get used to the influence of light, food intake is the main time cue and is closely linked to sleep.

In addition, the activity of the individual organs is also linked to the circadian rhythm. In traditional Chinese medicine, each organ has specific working and resting times. Energy flows through the body in 12 meridians (paths), each of which is connected to a body organ. If a particularly large amount of energy flows through, the organ is particularly active.

4. What influence does the internal clock have on sleep?

The internal clock regulates the sleep-wake rhythm and is largely oriented towards light and darkness. This means that it influences when we fall asleep in the evening and when we can get up in the morning. As long as it is light, the production of the "sleep hormone" melatonin is inhibited in the brain and cells. As the light exposure decreases (i.e. as it gets darker), melatonin production is reactivated, which prepares the body for sleep and causes tiredness. melatonin However, it does not make you tired, but rather prepares the body for sleep by regulating body temperature and activating cell metabolism.

This process can vary slightly from person to person, depending on their sensitivity to light. Therefore, chronobiology distinguishes between three chronotypes: The early, the late and the neutral types.

🌅 early type (lark)

Early risers are usually awake early, have little trouble with tiredness in the morning and can start the day quickly. They are physically and mentally capable in the morning. However, because of the early start to the day, tiredness sets in comparatively early in the evening.

🌇 late type (owl)

Late risers are still productive in the evening and only really get tired later in the evening. They usually reach their peak performance in the late evening hours and need longer in the early morning to wake up and get going. Because our social structures favor an early start to the day, evening risers in particular often have to forego important hours of sleep because the rhythm they live by does not match their natural rhythm.

⚪ neutral types (dove)

Most people are neutral types, which means they are neither extremely early nor very late awake.

5. Changes in the internal clock over the course of life

The basic temporal orientation and chronotype of a person are already determined from birth in the clock genes. In adulthood, light is the strongest and most effective clock maker. However, this ability must first develop in the first months of life. Up to about 6 months of age, babies a polyphasic sleep pattern - that is, they sleep in many shorter sleep phases that are spread over the day and night. After this, the so-called ganglion cells in the eye mature and the children slowly adapt to the light-dependent day-night cycle.

During puberty, the chronotype may temporarily shift slightly towards the late type. However, this is completely normal and we usually return to our original type by adulthood.

6thWhat happens when the internal clock is disturbed?

Disturbances of the circadian rhythm are becoming more and more common in today’s society. shift work, traveling across time zones (jet lag) or social obligations, we often live against our natural rhythm, for example by staying up too late in the evening, having to get up too early in the morning or working at times when our internal clock is actually set to rest and sleep. This disrupts the entire biological system, which can primarily lead to sleep disorders. Many other health problems can arise, not least due to disturbed sleep. It is therefore important to adapt to your own rhythm as best as possible and to prepare adequately for changes, such as a time change or long-distance travel.

You can find out how to get over jet lag as quickly as possible in this article.

7. Conclusion

• Chronobiology is about the temporal biorhythms of the body

• The internal clock consists of a master clock in the brain and many small clocks in the body cells & organs

• There are three chronotypes: early types, late types and neutral types

• Shift work, travel jet lag and social jet lag disrupt the internal clock and harm sleep and health