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What Is Circadian Clock And How Does It Work?

Updated: Sep 27, 2021

Have you ever wondered, why we sleep at night and are active during the day? Why do we start to feel sleepy at night and alert in the morning? How come that our body knows when to shut or turn on some systems?

See, our body loves routine. It works better when there is a cycle. Take sleep for instance.

Why do we sleep?

During the day, the body and the brain are attacked with pretty much everything. We work, walk, run, work out, do various tasks, process information, read, take decisions, eat, digest, excrete. These are all catabolic processes, meaning that the body is breaking down tissue and utilizing resources.

The night is the time to do the opposite. Sleep is anabolic. We rebuild the damages, heal the wounds, restore the sources back to balance. Something interesting happens with the brain though. During the day, our brain is exposed to a lot of information, and processing it, requires chemical reactions. These reactions, as we know from chemistry class, have always some by-products. In this case, those are toxic plaques that are building up in the brain and the only way to be removed is during sleep. The fun fact is that this plaque is one of the main causes of Alzheimer's, and funny enough, statistics show that people, diagnosed with Alzheimer’s disease, are usually people that have been sleep deprived for a good portion of their life.

Another interesting thing occurs. How do you think we learn stuff? We learn during the night. That’s right. During the night, the brain is not overwhelmed with the tasks of walking, working, processing information from the sensory input, such as hearing voices, seeing objects, etc… This means that the brain is now free to process the information that has been entered during the day, and decides which one to be stored in the long-term memories and be memorized, and which one to be forgotten.

We can’t really fight with nature and that is why we have been sleeping during the night, since our existence. There is no one that has hacked this system, and even if there is, I am not sure this is the right thing to do, but that is another topic.

The point that I am trying to make is that we do need this sleep-wake cycle. It is a routine that we must, and we do follow because this is how we are building.

But knowing a little bit more never hurts. In case you are interested, let's see how that cycle works.

Have you heard of the term circadian clock or circadian rhythm?

Circadian comes from the Latin “circa”, meaning around, and “Diem”, meaning day. So, around a day or 24 hours cycle. It is our internal clock, that synchronizes the body to the environmental changes. It prepares the body for sleep and starts up the systems that need to be running when we wake up in the morning.

Believe it or not, every living organism has it. It is first, witnessed in plants. Have you seen a sunflower? If you have a chance to observe one during the day, please do. It is pretty interesting. In the morning, you can literally see how the plant is still sleeping. Leaves are closed and the head or the inflorescence is tilted, facing down. As the sun is starting to rise more, so does the plant wakes up more. Leaves open, and the head is starting to follow the sun. You can literary see how in the morning the head is facing east and in the afternoon is already tilted west. As the sun goes down, so does the plant slowly starts to fall asleep. Leaves are closing and the head is tilting down.

It is a pretty profound experience. It shows how the plant is adapting to the sun and that mechanism is driven all by the circadian rhythm. All by its internal clock that is responding to the environmental changes.

Funny enough we, humans are the same. It is a bit more complicated than that, so let me explain.

The circadian clock is located deep into the hypothalamus. A small area located at the base of the brain that is connecting the nervous system and the endocrine system. That biological clock is connected to a group of nerves called the suprachiasmatic nucleus, which is connected to the optic nerve, which is allowing us to see and process light.

So, in the morning, when we wake up and the light goes through our eyes, the circadian clock senses that are time to wake up and starts to slowly turn on all the systems. Heartbeat, temperature, and blood pressure are raised and the production of the sleep hormone – melatonin is delayed.

As we are approaching the evening, our sensors are sensing the lack of light, therefore the circadian clock starts to slow down the functions of the organs and temperature drops down and the production of melatonin starts.

Of course, there is got to be a problem to address and here it is.

In our modern life, we often neglect that master clock and continue to expose ourselves to light at night. late work, night shifts, late studying, eating before bed, etc… These are all processes that are meant to be done when we are productive, focused, and alert. This disrupts and confuses the circadian clock, which ends up producing less melatonin. That results in less sleep or quality sleep and decrease productivity.

Scientists have recently linked diseases, such as diabetes, obesity, and dementia, to the disrupted circadian rhythm. It is pretty sad, knowing that if we simply listen to our body, we will drastically decrease the chances of having some very common diseases, that in fact, are treated with medical drugs and not with educating and changing living habits.

Take sleep for instance.

It is not hard to minimize light exposure late at night. Instead of watching TV, read a book, play games, talk with somebody. Instead of using strong white lights, use candles, or soft yellow lights. Try to not eat too late or right before bed. Simple small habits that can drastically change the quality of your life.

So, there you have it. An introduction to the circadian rhythm. I believe that if you know how your body works, you will be constantly seeking to become more tuned with it and listen to its signals. Do not underestimate your body. It is a very complicated machine, which is quite easy to operate.

Get to know it.


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