Our Circadian Rhythm and its Sleep-Wake Cycle

circadian rhythme and our sleep wake cycle

What is our Circadian Rhythm?

Every living creature on this Earth (that has a lifespan longer than a few days) will have an internal clock guiding their every waking, and sleeping, second. The body’s twenty-four-hour clock, also known as our Circadian Rhythm, keeps the entire system in check and directs every aspect of our life.

The most well-known function of the twenty-four-hour tempo is the ability to signal to our body when it is time to sleep and wake. But this inner rhythm also regulates our appetite, emotions and moods, body temperature, metabolic rate, and release of hormones. Even the pattern of births and deaths are linked to the circadian rhythm due to the regulation of these critical life-dependent processes.

A Cave-Dwelling Discovery for Science

Even if all outside elements are taken away, sunlight included, the body will still regulate itself based around this twenty-four-hour cycle. Two sleep researchers underwent an intense scientific study when they chose to separate themselves from the outside world and track how their bodies responded.

In 1938, Nathaniel Kleitman and his research assistant lived alone in an underground cave in Kentucky for 32 days to discover the exact effects of circadian rhythm, or sleep-wake cycle, on the body. What happens to a person when they do not have external environmental cues, such as sunlight and moonlight, to base their twenty-four-hour schedule around?

Known as the Mammoth Cave experiment, Kleitman and his assistant uncovered a deeper understanding of our inner clocks and their ability to regulate the body. The month spent in a dark cave illuminated a new understanding of this innate rhythm.

Surprisingly, for the entirety of the experiment, both men kept up a steady sleep-wake cycle. However, the body had a bit of leeway, and instead of a 24-hour period, it ended up being more of a 28-hour cycle. Even accounting for the added time, the conclusion that the human body can keep track and regulate schedules based on this rhythm was astounding.

Sunlight Exposure and Environmental Cues

The elongation of this cycle that Kleitman and his assistant experienced could be attributed to the lack of sunlight the scientists were exposed to. Even though it seems our body is quite capable of keeping somewhat on track, it is the sun that regulates us to twenty-four hours, resetting our inner clock with every sunrise.

However, the rising and setting of the sun is not the only factor that can regulate the circadian rhythm. Any activity you reliably repeat in a consistent matter becomes a cue for the brain to base it’s cycle off of.

When we eat, workout, and socialize can all affect our circadian rhythm and sleep-wake cycle. Together these daily, recurring activities will work in the same way that sunlight does to reset the clock back to its twenty-four-hour period.

Even the simplest biological forms on this Earth mimic this cycle. Unicellular organisms like bacteria, function in active and passive phases based around the light-dark cycle of the planet. We now believe that this governing pattern in single-cell organisms was the predecessor to our circadian rhythm.

The biological clock that keeps track of this cycle is located in the middle of the brain, called the suprachiasmatic nucleus. For playing such a crucial role in regulating the entire system, the suprachiasmatic nucleus is relatively small, as it is composed of 20,000 brain cells. This number may seem significant, but the brain is made up of over 100 billion neurons.

This tiny mind clock is what regulates the circadian rhythm, activating and deactivating both brain and body mechanisms based on this twenty-four-hour span.

Your Rhythm Guides Productivity

Just because every human has a biological clock governing the circadian rhythm, does not mean that each works according to the same sleep-wake cycle.

This becomes apparent when we consider whether or not we’re morning people. Almost everyone can pinpoint the time of day when they feel most awake, inspired, or productive. For some individuals, that’s early in the morning, for others the afternoon, or the evening. In this regard, we are all marching to the beat of our own twenty-four-hour drum.

By understanding the ebb and flow of your circadian rhythm, you could achieve more in a day, and attain a better sleep quality at night. Establishing a daily routine set around your unique sleep-wake cycle can help optimize every twenty-four-hour time span.
To help calculate your sleep cycle, use this sleep calculator.   To learn more about the body during sleep, head on over to our post about Understanding sleep