Thursday, October 15, 2015

Circadian Rhythm the Fortune Teller

            Despite the name, circadian rhythm has nothing to do with drums, counting beats or anything musical for that matter. Instead, it is one of the most complex, interesting and widely studied concepts in the biological and neuroscience fields. On September 22nd 2015, our neuroscience 300 class at Loyola University Chicago was lucky enough to have guest speaker Dr. Daniel J. Cavanaugh introduce the concept of Circadian Rhythms and explain his research as well.

            First, Dr. Cavanaugh defined what a Circadian Rhythm is. Also referred to as the biological clock, a circadian rhythm is a 24-hour cycle that regulated many physiological properties. The ’24-hour’ definition is based on the fact that the circadian rhythm is coordinated with the cycle of light (day) and dark (night) and thus carries out functions accordingly. An example of a physiological property that Dr. Cavanaugh supplies is the circadian rhythm regulates is hormone secretion for sleep. Melatonin is a hormone that functions in sleep and is actively released at nine o’clock at night specifically. With the increase of melatonin in the blood stream, you find yourself less alert and more tired. This is a classic example of the importance of the circadian rhythm. Melatonin is a hormone that helps the body to become less active and assist in entering sleep, thus it must be released during the night rather than during the day. Otherwise humans would not be able to function properly throughout the day but would actually feel less active and less alert. Another example is the function of the circadian rhythm in learning and memory in the fruit fly Drosophila. The fruit flies are conditioned to discriminate between two scents after one was linked with an electric shock punishment. This training induced a short-term memory regarding which odor produced which outcome, however the ability for the formation of this memory was dependent upon the circadian clock. The peak memory formation was specifically in either light dark or constant dark conditions, indicating that the circadian rhythms has influence over learning, and memory formation, as there are specific and optimal conditions.

            According to recent research, the circadian clock also functions in determining when an individual falls ill. Researchers at Yale University conducted a study that examined the success of a vaccination and its correlation to the circadian rhythm. The study found that the circadian rhythm influences the levels of a protein called TLR9, this is a protein that works with the immune system and the levels vary throughout the day. In the study, the mice were infected with bacteria in different times of the day, when TLR9 was at peak or when it was low. Results show that exposure to bacteria at low levels resulted in severe sepsis and sooner death than those exposed during high levels. Furthermore, the study also showed that vaccination during high levels of TLR9 resulted in a stronger immune response than vaccination during low levels. This is parallel to the fruit flies ability to form short-term memory at an optimal timing. Just as there is an optimal time for memory formation in fruit flies there is an optimal time for infection and vaccination. This is also parallel to Dr. Cavanaugh’s example; as there is an optimal time for melatonin release just as there is an optimal time for infection and vaccination.  

            Although there is ongoing research in circadian rhythms, the current studies and results represent the importance of the circadian rhythms. Circadian rhythms regulate physiological processes that vary from the immune system to the function of the brain. Circadian rhythms may not hold all the answers, however it is very possible that studying them will lead to other innovations that can answer many questions. For example, since circadian rhythms function according to timing, is there an optimal timing for cellular division to occur, with the appropriate functioning of the cellular division check points? If so, does this optimal timing reduce the risk of cancer? Hopefully, future research will answer such a minute question and other complex ones.

Citations:

O'CONNOR, ANAHAD. "WELL; Really? The Claim: Your Body Clock Can Determine When You Get Sick." The New York Times. The New York Times, 28 Feb. 2012. Web. 15 Oct. 2015.


Reece, Jane B., and Neil A. Campbell. Campbell Biology / Jane B. Reece ... Boston: Benjamin Cummings, 2014. Print.

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