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How knowing about circadian rhythms can help you get the right sleep pattern
How knowing about circadian rhythms can help you get the right sleep pattern

Neuroscientist Russel Foster explained what circadian rhythms are, why they go awry, and how it relates to sleep. Lifehacker publishes a translation of his article.

How knowing about circadian rhythms can help you get the right sleep pattern
How knowing about circadian rhythms can help you get the right sleep pattern

Circadian rhythms are the internal biological rhythms of the body with a period of about 24 hours. They prepare the body in advance, adjusting all physiological processes in accordance with daily changes in the surrounding world.

Almost all living organisms on the planet have circadian rhythms, including bacteria. In humans, the main circadian rhythm is the sleep-wake cycle.

Cell clock

At the molecular level, the body operates a circadian clock that triggers internal oscillation processes that regulate physiological processes in accordance with the external 24-hour cycle.

There are several types of clock genes that are responsible for the production of proteins. Their interaction creates a feedback loop that triggers 24-hour fluctuations in clock proteins. These proteins then signal to the cells what time of day it is and what needs to be done. This makes the biological clock go.

Thus, circadian rhythms are not the result of the joint work of many different cells, as was initially assumed, but a property of each individual cell.

For a circadian clock to be useful, it must be synchronized with signals from the outside world. The most obvious example of the discrepancy between the biological clock and the outside world is the jet lag.

When we find ourselves in a different time zone, we have to adjust our biological clock to local time. Photoreceptors (light-sensitive neurons in the retina) detect changes in the cycle of alternating light and dark and send signals to the circadian clock to adjust the body's biological clock in accordance with external stimuli. Adjusting the circadian rhythm ensures the correct functioning of all cellular processes.

Complex multicellular organisms often have a master clock that coordinates the work of all clock cells. In mammals, the main clock is the suprachiasmatic nucleus (SCN) located in the brain. The SCN receives information about light from the cells of the retina, adjusts the neurons in it, and they already send signals that coordinate the work of all other processes in the body.

Basic properties of circadian rhythms

1. Circadian rhythms are maintained under constant conditions of light or darkness in the absence of other external stimuli. This was discovered as a result of an experiment conducted in 1729 by the French scientist Jean-Jacques de Meran. He placed the plant in a dark place and noticed that even in constant darkness, the leaves open and close in the same rhythm.

This was the first evidence that circadian rhythms are of internal origin. They can fluctuate and, depending on the species, be slightly longer or shorter than 24 hours.

2. Circadian rhythms are independent of outside temperature. They don't slow down or speed up to a large extent, even when the temperature changes dramatically. Without this property, the circadian clock would not be able to tell time.

3. Circadian rhythms can be assigned to the outer 24-hour day. In this case, the main signal is light, although other signals also have an effect.

Significance of circadian rhythms

Having a biological clock allows the body to anticipate predictable changes in the environment and to pre-tune behavior to account for these conditions. For example, knowing that dawn will come in three hours, the body begins to increase the metabolic rate, temperature, and increase blood circulation. All this prepares us for vigorous activity during the day.

In the evening, when we are getting ready for bed, the physiological processes in the body begin to slow down. During sleep, the brain is actively working. It captures memories, processes information, solves problems, sends signals to repair damaged tissues, and regulates energy stores. Certain parts of the brain are more active during sleep than during wakefulness.

Circadian rhythms and sleep

The sleep cycle is the most obvious circadian rhythm in humans and animals, but it depends on more than just circadian rhythms.

Sleep is an extremely difficult condition that occurs due to the interaction of various areas of the brain, hormones and the neurotransmitter system. Because of its complexity, the sleep cycle is very easy to upset.

Recent studies have shown that sleep and circadian rhythm disturbances are common in both neurodegenerative and neuropsychiatric disorders in which neurotransmitters do not work properly. For example, this disorder is typical for more than 80% of patients with depression and schizophrenia.

But the inconvenience caused by feeling sleepy during the day is a trifle. Disruption of sleep and circadian rhythms is also associated with a whole range of pathologies, including depression, insomnia, impairment of attention and memory, decreased motivation, metabolic disorders, obesity, and problems with the immune system.

How to adjust your biological clock

Scientists have long wondered how the eye detects light to adjust circadian rhythms. Recently, special light-sensitive cells have been discovered in the retina - photosensitive retinal ganglion cells. These cells are different from the rods and cones that scientists have known for a long time.

Visual stimuli, perceived by photosensitive ganglion cells, travel from the eye to the brain via the optic nerve. But 1-2% of these ganglion cells contain visual pigment that is sensitive to blue color. Thus, photosensitive ganglion cells record dawn and dusk and help to adjust the body's biological clock.

Due to the modern lifestyle, we often do not get enough light, spending most of the time indoors. This may be the reason that our clock is not setting correctly.

Research has shown that eating at the same time and exercising in the morning can help you develop proper sleep patterns.