Does your body run according to certain patterns? Maybe you’re always ready for bed at 9:00 PM or you feel like you need a nap every afternoon. These are both examples of your circadian rhythms at work. However, these complex bodily systems manage more than just sleep and wakefulness. In fact, researchers are learning more and more about circadian rhythms all the time.

What is a circadian rhythm?

A circadian rhythm is any pattern in your body that follows a daily cycle. These can be physical, behavioral, mental, or psychological. Nearly all living things studied thus far have some sort of circadian rhythm. This includes animals, plants, and microorganisms, too. Circadian rhythms seem to be related to cycles of light and dark that come with day and night.

Is a circadian rhythm the same as a biological clock?

Your biological clock is how your body tells time internally. You may not always know exactly what time it is on the external clock, but your body is always tracking the time of day and what should be going on based on what time it is.

Nearly every organism studied so far has a biological clock. Individual tissues and organs seem to have them, too, though whether these are truly independent remains to be researched.

Your biological clock runs or drives your circadian rhythms, but is not identical with them.

How do circadian rhythms work?

Researchers are still studying the exact method by which circadian rhythms work. They know that the biological clock is managed by a structure in the brain called the suprachiasmatic nucleus (SCN). This is made up of over 20,000 neurons and is located in the hypothalamus. It interacts with the eyes, thus getting direct knowledge of what the external light is doing. This structure functions as a sort of master clock for the entire body.

The SCN, in turn, seems to direct certain proteins in the body. These bind to cells or don’t bind to cells, which tells them what to do or not do. At different times of day, these proteins interact with cells differently. This seems to set the circadian rhythms.  

What do circadian rhythms control?

Circadian rhythms control when we sleep and when we wake up. They also play a part in controlling when we release certain hormones, when we feel hungry and how and when we digest our food, and our body temperature, which goes up or down based on the time of day. Circadian rhythms can also affect our energy levels, causing many people to need rest or food in order to keep going through the middle of the afternoon.

How do we make our circadian rhythms?

We don’t have a lot of choices as far as the circadian rhythms the body sets. The determining factor seems to be whether or not particular types of light are present. Light and the lack thereof trigger certain genes to turn off or on. These genes control our internal biological clock, which then controls the body. As cycles of light and dark change, both biological clocks and circadian rhythms can be made faster, slower, or even reset entirely.

How do circadian rhythms affect health?

When our biological clocks are too fast or too slow, our circadian rhythms get off balance, too. Disrupted rhythms are closely associated with health problems including depression, obesity, bipolar disorder, and diabetes. While researchers don’t know exactly how a disrupted clock helps cause these problems, it definitely seems to play a part.

What do circadian rhythms have to do with sleep?



Circadian rhythms are one of the basic mechanisms that tell us when to sleep and when to wake. The SCN tells the body to produce melatonin, a hormone that helps us sleep, when there is less light reaching the eyes. It limits melatonin production when there is plenty of light.

Some people, like shift workers, manage to disrupt this cycle long term. Researchers are studying what goes on in their brains to allow that. They are also studying how the light from electronic devices mimics sunlight and lowers melatonin production.

How do circadian rhythms help us recover from jet lag?

Jet lag happens when our biological clocks and circadian rhythms get out of sync because of travel. Light comes in through the eyes when the body doesn’t expect it, or it doesn’t come in when the body does expect it. Either way, we feel sleepy at the wrong times and generally disoriented. Since the circadian rhythms can be reset by light, they slowly help us recover our equilibrium.

Circadian rhythms are complex, and the emerging research on them is fascinating. As we learn more about how the body manages its circadian rhythms, we may also learn more about how we can get more sleep, better rest, and how we can care for ourselves well.

by: Sarah Winfrey