Often referred as body clock or internal clock is the 24-hour cycle that tells our bodies when to sleep, rise and eat. It determines whether the person feels wide awake, energized or sleepy. It is affected by many environmental cues which are called zeitgebers like sunlight and temperature. Sun is the primary influence on circadian rhythms but there are other social cues, eating cues, exercise or activity cues.
Circadian Rhythms govern by Suprachiasmatic Nucleus (SCN), located in the hypothalamus region of the basal forebrain. It acts as a chief executive officer, instructing the rest of the body to stay on schedule and incorporate cues from the environment
But how was it discovered? Let's find out.
In 1729, French scientist Jean-Jacques d’Ortous de Mairan recorded the first observation of an endogenous or built-in circadian oscillation in the leaves of Mimosa Pudica. Even in total darkness, the plant continued is daily rhythm. This led to the conclusion that the plant was not simply relying on Zeitgebers, But also has its own Internal Biological Clock.
Two hundred years later, in the mid-20th century, the field of chronobiology blossomed and benefitted from the contributions from many scientists, Notably by Colin Pittendrigh who is also known as the father of biological clock. He studied the fruit fly Drosophila and shed light on how circadian rhythms entrain or synchronize to light and dark cycles. John woodland Hasting also made an important foundational discovery about the role of light in Circadian Rhythms by studying Luminescent Dinoflagellates, A type of plankton. Erwin Bünning, who studied plant biology, also contributed to the foundational Research in entrainment modeling, describing the relationship between organism and light and dark cycles.
The next phase of chronobiology discovery began to articulate the specific molecular and genetic mechanisms of circadian rhythms. This came from the work of Ronald J. Konopka and Seymour Benzer, who in the early 1970s aimed to identify specific genes that controlled the circadian rhythms in fruit flies. Konopka and Benzer are credited with discovering a mutated gene, which they called period. This was the first discovered genetic determinant of behavioral rhythms.
Jeffrey C. Hall, Michael Rosbash and Michael W. Young expanded Konopka and Benzer’s work by successfully showing how the period gene worked on the molecular level. Hall, Rosbash, and Young — were also awarded the 2017 Nobel Prize in Physiology or Medicine
Jumping from fruit flies to mice, Joseph Takahashi and his team discovered the mammalian clock gene in 1994. This gene discovery, along with the body of work by Hall, Rosbash, Young and the scientist Michael Greenberg, led to a watershed in chronobiological knowledge.
After that, researches and studies are being conducted and new things are discovered steadily.
But after all of this, the question arises why we need to take care of our Circadian Rhythms. Well,
A healthy Circadian rhythm improves alertness, coordination, cardiovascular efficiency, immune system, consistent bowel movements, and sleep. In the long term, it reduces the risk of chronic diseases. It is also correlated with neurological problems, Disrupted circadian Rhythm causes problems like depression and bipolar disorder And other problems like Diabetes and cardiovascular diseases.
