Does the human body really have a 24-hour body clock?

There is a time for everything. For each activity every day, we know when is the right time to do it.  The right timing always matters.

The concept of time started since early humans first noticed the regular movement of the Sun and the stars. Some 30 000 years ago, prehistoric people first recorded the phases of the Moon.

Some recognizable natural phenomenon was initially seen in the heavens, but many other events indicated significant changes in the environment over time. Events and naturally occurring patterns led to the season’s recognition were also determined, such as the seasonal winds and rains, the flooding of rivers, the flowering of trees and plants, and the breeding cycles or migration of animals and birds. These events also led to the natural divisions of the year.

One of the earliest measuring time methods was referencing using the Sun, the Moon, and the stars. The Sun’s light causes a casting of the shadow of any object on Earth, and as the Earth rotates and changes position, the shadow also changes its position, indicating a change of time.

There were different instruments and methods used in telling the time. These had included the use of oil lamps, candle clocks, water clocks, hourglass, sandglass, and pendulum. We had our first mechanical clock in 1716. John Harrison, a carpenter, and instrument maker, built a marine chronometer with a spring and balance wheel escapement that kept very accurate time.

More than these devices and ways of determining a particular time, our body itself has its internal clock. It’s incredible how our minds can identify the time without looking into a clock or a watch.  Humans or even animals have that innate ability to tell what time of the day it is. More so, our body can tell where it’s time to sleep, or it is time to wake up.  Thanks to our body clock!

Our body’s internal clock or the circadian rhythm is a 24-hour cycle running in the background to carry out essential functions and processes. Our sleep and wake cycle are one of the most essential and well-known circadian rhythms. Our body’s system follows a circadian rhythm synchronized with the brain, the master clock.

Environmental cues, especially light, directly influence the brain. This is the reason why we can easily tell when it is night time as the light of the day disappears. Besides external cues, there are clear hormone production patterns, cell regeneration and brain wave activity, and other biological activities that are linked to this daily cycle.

Properly aligned circadian rhythm can promote consistent and restorative sleep. But when it is thrown off because of some factors, it can create significant sleeping problems.

How Does Circadian Rhythm Work?

Circadian rhythms came from a Latin phrase “circa” and “diem,” which means “around” and “a day.” This internal body clock functions by ensuring that the body’s processes are optimized at various points for 24 hours.

Not only humans possess this innate quality. Plants and animals and other organisms also have a circadian rhythm. Some flowers know when its morning, they open their flowers when the sunlight out. Likewise, nocturnal animals tend to leave their shelter during the day as there will be more predators to hunt them.

The circadian rhythms in humans harmonize mental and physical systems throughout the body. The digestive system knows when to produce proteins to match meals’ typical timing, and the endocrine system regulates hormones to suit normal energy expenditure.

There is a “master clock” where the circadian rhythm is connected to. It is located in the brain and sometimes referred to as the circadian pacemaker. This master clock is specifically set in the suprachiasmatic nucleus (SCN), which is part of the brain’s hypothalamus.

The high sensitivity to light makes the SCN a critical external cue which influences the signals sent by the SCN to coordinate internal clocks in the body. This also makes the circadian rhythm closely connected to the changing of day to night. While other cues, like exercise, social activity, and temperature, can affect the master clock, light is the most powerful influence on circadian rhythms.

Another factor is the activation of genes that triggers the production of proteins. The genes switch off when protein levels build up to a critical threshold in the cells. Over time, the proteins degrade that allows the genes to switch back on, and the cycle starts again. This takes about 24 hours.

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