Our circadian rhythms are the physical, mental, and behavioral change that follow a daily cycle. These circadian rhythms drive all organic cues in your body. The cues that your body responds to includes your sleep patterns, eating habits, and mental state. Have you ever noticed that you always tend to get hungry at the same time each day... or start getting sleepy at the same time each night? These are cues from your own internal circadian rhythms.
These cues can also drive the internal actions of the body, such as body temperature, blood pressure, hormone production, digestion, and immune responses. Researchers have even been able to observe the impact of the circadian cycle outside of the body on human tissue cells taken from a biopsy. These cells continued to cycle outside the body even when they were placed in a petri dish! So you can see how powerful the effects of exposure to circadian rhythms are.
The circadian rhythm cycle takes place over a 24-hour period. During this time, your body undergoes daily changes to maintain an internal balance that includes hormone release, digestion, temperature, and sleep-wake cycles. The most well-known impact of the circadian cycle is on your sleep patterns. Your master clock controls the production of melatonin, the hormone that makes you sleepy. The production and release of melatonin depends on your optic nerves, which is why you begin to feel sleepy when it is dark outside. It is your circadian clock telling your body that it is time to sleep!
A prolonged disruption between the sleep-wake cycle and light-darkness cycle can even cause Circadian Rhythm Disorders. Internal factors (such as sleep disorders) or external factors (due to jet lag, overnight shift work, etc.) may be the cause of this mismatch, but this disconnect from your normal circadian rhythms can cause harmful interruptions in the normal patterns of your body.
These circadian rhythms are so important that, in fact, the 2017 Nobel Prize in Medicine was awarded to researchers who studied it. The American biologists, Jeffrey Hall, Michael Rosbash, and Michael Young, shared the prize for their research into the structures that drive our 24-hour cycles. This research has stemmed into a whole new field – chronobiology – which studies how people (and other organisms) track time and adapt to changes in these natural cycles.