Do you go to bed at the same time every night? Or, even if you don’t go to bed, do you feel sleepy about the same time every night? That’s because your circadian rhythm is telling you it’s time for bed.
Circadian rhythms manage all sorts of things in the human body, and the sleep-wake cycle is just one. Knowing more about them can help us understand how the body works, so we can help ourselves get more good rest every night.
Circadian Rhythms and Biological Clocks
A circadian rhythm is anything that the body does that is based on a daily cycle. These patterns can be mental, physical, behavioral, or even emotional.
Your circadian rhythm and your biological clock are not identical. In fact, your biological clock basically runs your circadian rhythms.
The biological clock is kind of like the clock on your wall but inside your body. It may not know exactly what time it is, but it knows when it’s time to do things like eat and sleep. The clock, then, sets the rhythms that our bodies stick to every day.
The biological clock is run by a set of 20,000 neurons in the brain. These form a structure called the suprachiasmatic nucleus, or SCN, which is part of the hypothalamus. The SCN is connected directly to the eyes, so it is constantly receiving information about how light and dark it is.
This is key since the biological clock runs based on light and dark cycles. When it’s light, it tells your body to do certain things. When it gets dark, it tells it to stop some of those things and start doing other things. It communicates with the rest of the body by sending proteins throughout the system. These bind with cells to signal to them that it’s time to perform certain functions, or stop performing them.
Almost all organisms have circadian rhythms and some sort of biological clock to regulate them. Humans, animals, plants, and even fungi and microorganisms function in these regular, repeated patterns.
Circadian Rhythms and Health
The biological clock manages circadian rhythms throughout the body. These control when we release certain hormones, when we eat and how we digest when we do eat, our body temperature, and more. This is on top of controlling when we sleep and when we wake.
All of these rhythms are controlled by daylight. When the SCN gets notice via the optic nerve that it’s light outside, it makes changes to genes that control the biological clock which, in turn, signals the circadian rhythms.
When something goes wrong in this cycle – when the biological clock is off or the circadian rhythm becomes too long or too short – the body suffers. In fact, messed up circadian rhythms correlate with all sorts of conditions, including diabetes, depression, bipolar disorder, seasonal affective disorder, and sleep disorders.
Researchers are not yet entirely clear how the circadian rhythms get off or how that coincides with these health conditions. What they do know is that, sometimes, it’s possible to reset a circadian rhythm. Time a person’s exposure to light correctly and the body may be able to fix an out-of-sync rhythm.
Circadian Rhythms and Sleep
One of the most important bodily functions regulated by circadian rhythms is sleep. When the light begins to face, the SCN takes note. It tells the brain to begin producing more melatonin. As it gets darker and darker outside, it tells the brain to ramp up this production. Since melatonin makes you sleepy, this is an important part of getting the rest you need.
In our modern culture, we disrupt this process all the time. Blue light, which is the light emitted by mobile phones, laptop screens, television screens, and more, comes into the eyes similarly to sunlight. Thus, if we are looking at screens after dark, the body doesn’t always know it’s nighttime and doesn’t always produce the melatonin that we need in order to sleep.
There are ways around this since not all light is processed that way. Using some sort of nighttime filter on your phone and even on your TV can help your brain know when it’s time to rest.
We also disrupt these cycles when we travel, hence jet lag. Fortunately, the new light-dark cycles in our new location will reset our rhythms after a few days. Until then, though, we feel tired and sluggish when we want to be awake.
If you feel like your circadian rhythms may be off, talk to your doctor. There’s hope that light therapy, or refraining from blue light use before bed, could help your body reset itself. As researchers learn more about these rhythms, there should be more treatments available to help people who aren’t getting enough sleep because their circadian rhythms aren’t working right.