Have you ever noticed that your body seems to do certain things around the same time each day? You wake up around the same time, get hungry around the same time, and are tired and ready for sleep around the same time. This is thanks to biological processes that keep your body in lock step as the day progresses, also known as your circadian rhythm.
From fruit flies to daffodils to microscopic organisms, if it lives under the sun chances are there’s something that keeps it in tune with the sun’s 24-hour pattern. In humans, there are proteins in nearly every tissue and organ that help maintain proper timing, but they don’t function independently. Inside your brain is something like a master clock that all other biological clocks sync up to. This master clock is called the suprachiasmatic nucleus, and it’s made up of around just 20,000 neurons arranged in two tiny wing-like structures nestled inside your hypothalamus.
In the suprachiasmatic nucleus there are proteins produced on a negative feedback loop. The proteins switch off their own production when they build up, and cells resume production once the proteins degrade. These protein cycles peak about every 24 hours, though it’s not exact.