Body processes

Resynchronization – Function, Task & Diseases


Like all other living beings, humans also have a circadian clock . The rhythm of the clock is synchronized with the 24-hour rhythm of the day by means of timers such as light and temperature. Problems with resynchronization can cause significant ailments, such as depression .

What is resync?

The circadian rhythm is also known as the inner clock. It prepares the human organism for daily recurring phenomena. The circadian clock controls not only the heart rate , but also the sleep-wake cycle , reproduction , blood pressure and body temperature . The organism moves largely independently of external influences at the time and carries out periodic activities with a relatively constant rhythm.

genetic basis controls period length. However, in order for the rhythm of the internal clock to actually fit the 24-hour cycle of the day, constant resynchronization of the circadian clock is required. This resynchronization is necessary above all against the background of changing day lengths over the course of the year.

The photoreceptors in the outer nuclear layer of the retina are mainly involved in resynchronization. The light and its changes are thus used as a circadian timer to resynchronize the internal clock. Since the period length of the internal clock is not exactly 24 hours, a lack of readjustment or a lack of resynchronization causes the organism to lose its rhythm.

In addition to humans, animals and plants also adapt their rhythm to the day-night cycle via the circadian clock and its automatic readjustment.

function & task

In plants, the photosynthetic apparatus is activated before sunrise and thus prepares the organism for the start of photosynthetic activities, which can only be carried out during daylight. Some plants open or close flowers at certain times of the day or produce nectar at certain times. 

The existence of a free-running circadian rhythm under constant conditions today leads scientists to assume that there is a rhythm-generating inner unit. According to current knowledge, this control unit is located in the central nervous system . In mammals, the switching point of the circadian clock is probably located in the suprachiasmatic nucleus of the hypothalamus . From here all other circadian pacemakers of the periphery are coordinated.

The molecular clock works according to transcription – translation feedback. The protein translation inhibits the transcription of the involved genes for the respective protein. In addition to CLOCK, BMAL1 and PER, the key proteins involved are presumably CRY and NPAS2.

The feedback sequence of the molecular coupling mechanism takes around 24 hours. In addition to temperature changes and light, these temporal sequences are indirectly synchronized by neuronal and hormonal signals. Because the external cause of circadian rhythms is the planet’s own rotation, the most relevant external rhythm generator is the changing illumination intensity of the atmosphere. The visual system recognizes this pacemaker. The light is therefore probably the most relevant and universal timer for the resynchronization of the internal clock. If it is evening or night according to the internal clock, but the retina still detects light, the internal clock is adjusted. This allows the organism to adapt to the change of seasons.

The resynchronization of the inner clock is necessary for numerous bodily processes. Accordingly, a lack of resynchronization can have serious consequences.

Diseases & Ailments

People are particularly susceptible to circadian clock resynchronization problems because of their lifestyle. Above all, modern life throws the body clock out of balance and can thus have a negative impact on well-being and health . Problems with resynchronization arise, for example, after long-haul flights. After a trip to a different time zone, the internal clock no longer agrees with the prevailing day-night rhythm . The resynchronization must take place in the short term. Jet lag is a consequence of these connections. 

Shift work presents a similar problem. Shift workers live in opposition to their inner rhythm. People are also spending less and less time in daylight. Especially in winter, the light intensity indoors is hardly higher than 500 lux. At night, modern people are permanently exposed to artificial light stimuli. The daily resynchronization of the inner clock is often confused because of these connections. In addition to sleeping and eating disorders , lack of energy and even depression are favored by resynchronization problems . Metabolic stress can also be a consequence of resynchronization problems. Diabetes mellitus andFavors obesity .

A particularly well-known primary disease associated with resynchronization is the circadian sleep-wake cycle disorder. Sufferers of these sleep disorders are unable to fall asleep when sleep is wanted or needed. When alertness is required or expected, they are sleepy and can barely keep their eyes open. This phenomenon is particularly common in the context of shift worker syndrome or affects frequent travelers with regular jet lag experiences.

There are two different types of sleep disorders. While one is characterized by delayed sleep phases , the other is characterized by advanced sleep phases.

Because blind people have a much harder time resynchronizing than sighted people, circadian sleep disorders affect them significantly. If left untreated, the sleep disorders can trigger a number of psychological and physical complications over the long term.

Lisa Newlon
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Hello! I am Lisa Newlon, and I am a medical writer and researcher with over 10 years of experience in the healthcare industry. I have a Master’s degree in Medicine, and my deep understanding of medical terminology, practices, and procedures has made me a trusted source of information in the medical world.