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How Light is Used in The Circadian Rhythm

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Table of contents

  1. Introduction
  2. Background
  3. Effects on Other Biological Processes
  4. Illnesses that Originate from Nonregulated Circadian Rhythms
  5. Conclusion


The Circadian Rhythm is a biological tool that is a part of just about every living organism on Earth. While each being experiences it differently, humans are unique in the sense that we use ours for our day-night cycle. The Circadian Rhythm is responsible for our sleep cycle and how it is maintained. Using the suprachiasmatic nucleus, or SCN, the brain creates this sort of internal clock that helps an organism control its bodily functions. Current studies are underway in order to gain a better understanding at how this works as well as it’s connection to other bodily functions such as sleep and metabolism. Light is an important factor that takes a big role in the Circadian Rhythm in not just humans, but in all organisms. Melatonin is also a very important tool for this as it aids in the resetting of this internal clock. Without this internal clock there would be no way to maintain bodily stasis and would lead to serious health complications. Therefore, this is a crucial neurological body function that is absolutely necessary in order to properly sustain oneself.


Light is a very powerful force that can affect various parts of life. One of its most important roles is when it controls our circadian rhythms. Humans are very unique as we are some of the most insensitive organisms when it comes to light. However, this insensitivity is not affected by the fact that it affects how humans sleep. As light is observed, this goes through the brain and causes a repression of the posterior hypothalamus. The posterior hypothalamus is what aids in the secretion of melatonin, which is the biological chemical that the brain creates in order to aid with our sleep cycles. When there is less light being observed, there is a lot more melatonin being created causing the organism to be more tired. In a more detailed explanation, light enters through the retinal glands and is dispersed through the form of ganglion cells. After this step, they are then sent to the SCN, which is linear with its connection to the posterior hypothalamus. This then explains the process in which light and SCN are connected. With this set, scientists are able to find treatments for those who are experiencing difficulties with their circadian rhythm.

It is imperative that the body regulates its circadian rhythm each time as it could begin to lead to other health issues such as insomnia, diabetes, obesity, and so forth. Jet lag is a very good example of what could happen whenever the body’s internal clock goes temporarily wrong. A person experiences the lethargic effects of jet lag when they have traveled across one or more time zones. Because a person’s body is used to their respective time zone, a period of adjustment is necessary to maintain a healthy sleeping stasis. Since the body is used to sleeping at a different time, when it experiences this lag, it has a detrimental side effect that takes several days to get used to. Not only is jet lag associated with travel, but also with people who work shifts that alter their sleeping patterns such as doctors and nurses. These people also experience their own form of jet leg without needing to travel through time zones and the same effects apply.

Effects on Other Biological Processes

This not only affects the way humans sleep, but the way the body metabolizes and processes food. Two genes (CLOCK and BMAL1) within the body’s metabolism work together in order to properly connected with the body’s circadian rhythms. BMAL1 is used in order to sort of kick start the metabolism in order to let the body be alert, hungry, and essentially on the go from the waking minute. In a study on mice, it was found that when these two genes or receptors were turned off, their biological systems went out of control. REV-ERBα and REV-ERBβ were two cellular switches within these mice that were also correlated with their circadian rhythms. When these switches were turned off the scientists noticed that the mice were beginning to exercise when they were supposed to be resting. Also they noticed that fat and bile were beginning to build up. This experiment was done in order to find the correlation between metabolism related diseases with the circadian rhythm. Their results supported the argument that both were interrelated. As known, the body does the majority of its work while it is at rest. When the circadian clock is compromised or altered in a negative fashion this begins to affect the way the body works. If the body is not getting enough rest this could begin to lead to lethargy and obesity in a person. Therefore, it is important to lead a normal sleep schedule in order to maximize the usefulness of the metabolism.

Illnesses that Originate from Nonregulated Circadian Rhythms

The Circadian Rhythm is mainly determined by genetics; however, it is influenced highly by the organisms use of it. For example, it must be calibrated each cycle in order for it to work properly. Most clocks tend to run just about 24 hours each cycle, but not quite. The way the rhythms work is very easy to change and are adaptable to the person’s lifestyle. However, with this can be altered by certain factors such as work scheduling issues, school, or other social commitments. Diseases such as diabetes, insomnia, obesity can also lead to an imbalance in the circadian rhythm. An imbalance can also lead to these diseases as well. There are treatments to help prevent this from happening. It is important to adjust one’s schedule in whatever form that appears to be the best. Light treatment is also used to in order to shift the circadian rhythm to a more stable one. Light treatment is very effective, but it is mainly used for extreme disorders and should only be done after being evaluated and treated by a professional doctor. When a patient is undergoing light treatment they are simply shown bright lights at certain times of the day depending on the severity of their condition. For example, a person with an advanced sleep disorder would receive bright light treatment in the evening in order to push their circadian clock further. A person who is experiencing a delayed sleep disorder would then receive treatment in the morning in order to shift the clock backwards. Once again, these treatments are considered highly effective, but should only be done after consulting with a primary healthcare physician. For less severe cases, melatonin treatment is also an effective solution. Since the SCN produces melatonin, it is a harmless chemical that the body produces and taking melatonin only produces more of it. Melatonin is then spread throughout the body in order to reset the clock and cause the user to get tired faster. Another form of treatment would be to simply adjust one’s sleep schedule to a more appropriate time as this is often the main issue.


Overall, the Circadian Rhythm is an important part of our lives and controls some of our most important bodily functions: sleep and metabolism. Using light in order to produce melatonin through the posterior hypothalamus and the SCN, this regulates our clock in order to ensure that our bodies are maintaining stasis in the best way possible. Studies are even being conducted in order to show what kind of issues could arise if the circadian rhythm was disrupted as well as its connection to other bodily functions. These studies are producing results that are helping scientists making further hypotheses on how to understand it. Failure to get this clock in order could lead to detrimental health effects such as insomnia, diabetes, or obesity. Jet lag is also a temporary issue that may occur if one’s rhythms is imbalanced. Treatments are available in order to help regulate the rhythms however, none are as effective as simply getting the necessary rest and following one’s clock as closely as possible. Light therapy for different severity cases also produce results, but as aforementioned, resetting the clock will produce better results. With future developments scientists will soon be able to fully understand the circadian rhythms and its neurological connection to the body.

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How Light Is Used In The Circadian Rhythm. (2019, March 12). GradesFixer. Retrieved March 26, 2023, from
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