Have you ever flown on an airplane? It can be so much fun to soar through the air in that big metal tube and land somewhere hundreds or even thousands of miles away…all in a matter of a few hours!

If you know someone who has to travel frequently for business purposes, however, you'll find that the allure of flying on an airplane can wear off fairly quickly. For example, if you have a flight that leaves New York City early in the morning and lands in Los Angeles several hours later, you might find that you have trouble going to bed and waking up at the usual time.

Frequent travelers call this effect jet lag. After a long day of travel, you might be ready to go to bed at 10 p.m. New York time. Unfortunately, that's only 7 p.m. Los Angeles time. If you don't go to bed until your friends from L.A. do, you'll be super tired the next day!

Jet lag is just one of the things that can happen when our circadian rhythms get disrupted. Circadian rhythms are our bodies' physical, mental, and behavioral processes that follow a cycle that's approximately 24 hours long.

These cycles tend to correspond to light and darkness in our environment. Circadian rhythms can be found in almost all living things, including animals, plants, and even tiny microbes. There's even a special branch of scientific study dedicated to circadian rhythms, known as chronobiology.

Sometimes people confuse circadian rhythms with biological clocks. They're not the same thing, but they are related. Our bodies' biological clocks are what drive our circadian rhythms.

These biological clocks are made up of groups of interacting molecules that exist in cells throughout our bodies. A "master clock" in the brain, known as the suprachiasmatic nucleus or SCN, consists of about 20,000 nerve cells in the hypothalamus. It controls all circadian rhythms and keeps all the body's biological clocks in sync.

Circadian rhythms are triggered by both external, environmental factors, such as sunlight, and internal, biological factors. For example, when sunlight decreases toward the end of the day, the SCN stimulates production of melatonin, a hormone that helps to make you sleepy. In addition to sleep cycles, circadian rhythms influence body temperature, the release of hormones, and other key body functions.

When circadian rhythms get disrupted, a variety of negative consequences can result. Various health issues that have been linked to circadian rhythm disruptions include insomnia, obesity, diabetes, depression, bipolar disorder, and seasonal affective disorder.

Scientists who study chronobiology have determined that there is definitely a genetic component to circadian rhythms. As they seek to identify particular genes that control these important processes, they are hopeful that they will be able to develop new treatments for a variety of health issues linked to circadian rhythms.

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