What Is A Circadian Rhythm?

Circadian rhythms describe regular events that happen to all humans, plants and animals on a daily basis. We are far from understanding all of them and their effects on our health but we know that there are processes that happen in all of us on a roughly 24 hour cycle influenced by various cues from our environment. The influence of these rhythms can change sleep and wake cycles, release various hormones, influence body temperature and regulate other important bodily functions. While we all have circadian rhythms there are some differences in the length of the cycles which helps to explain why some of us are “night owls” and others are “morning people”. There also appears to be a genetic component to our rhythms which explains why some lifestyle habits such as staying up late appear to run in families.

The image below shows many of the circadian rhythms:

bodyclockguide

From the image we can see regular changes in melatonin secretion, body temperature, vascular changes and bowel changes among others. For example, melatonin secretion starts around 9pm and ceases around 7:30am with our period of deepest sleep at 2am. This sets in place a natural sleep cycle for us as humans. For those of us who work late hours or third shift we are in direct contention with this natural cycle and this may lead to issues with sleep or other aspects of our health.

We also see that our lowest body temperature is at 4:30am and our highest is at 7pm. This natural temperature variation allows for many processes in our body to function correctly, yet our temperature controlled environments may not always cater to allowing these functions to completely take place. This, again, is another example of possible disruptions.

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