All living things are guided by an internal mechanism referred to as our biological clocks. Our internal clock tells us when to sleep, eat, wake and perform all of our other daily activities. Body clocks, or circadian rhythms, have been observed in a variety of organisms, including animals, plants, cyanobacteria and fungi. The term circadian comes from the Latin term circa, meaning “around” and dies or diem, meaning “day.” Internal clocks are highly important to an individual’s health as they help to regulate many bodily functions, such as eating and sleeping.

What Is an Internal Clock'

Internal biological clock, also referred to as a circadian rhythm, is a term used to describe the twenty-four hour cycle living organisms experience as the body adjusts from day (light) to night (dark) as the Earth rotates. An individual’s internal clock is constant and is generally determined by external stimuli and natural biological functions. An internal clock consists of three parts: a time-keeping mechanism, a method of receiving temperature, light and other environmental input and genes that aid the clock in managing the activity of other genes. Studies have shown that the genes responsible for running an internal clock include clock (clk), period (per), timeless (tim), doubletime (dbt), cycle (cyc) and frequency (frq), among others.

Why Is It Important'

When the internal clock is in sync with an individual’s daily patterns, activities required to sustain life stay more or less on schedule. For example, a person may awaken naturally around the same time each morning and become tired at the same time each night. Cravings for food may also begin at certain times during the day in which you typically eat meals or snacks. Internal programming in combination with external stimuli helps to keep the internal clock functioning smoothly, thus keeping the body healthy.

How and Why Is It Different Per Individual'

Internal clocks are hard-wired into our brain for survival but can differ among individuals. External factors can cause the internal clock to become modified. For example, individuals working the night shift may find it difficult to get proper rest at first as their internal clock is set to wake when it’s light and sleep when it’s dark. Internal clock modification can also affect travelers. As a person moves from time-zone to time-zone, their natural rhythm may become unbalanced, leading to jet lag. In this situation, the person may feel tired and could experience spurts of insomnia as their body adjusts to the new time-zone.

Can It Be Adjusted and If So, How'

At times, we may have the need to tweak our internal mechanism to better suit our lifestyle, such as getting up earlier for a new job. Repetition of several activities can help an individual to permanently adjust their internal clock. Individuals should continue to get a normal amount of sleep but shift their ordinary sleep pattern to properly separate wake-up time from sleep-time. Individuals can use certain tips to help them re-adjust their sleep time, such as blocking out all light from their bedroom. Upon waking up, the body should be immediately exposed to light, whether natural sunlight or artificial.

Interesting Facts

Internal biological clocks have been recognized in plants for nearly 300 years, but only towards the 1950s did scientists discover them in animals. In 1988, scientists established the first clock gene in mammals with the existence of mutant hamsters that had a 20-hour circadian rhythm. At the University of Utah in 2001, scientists found the first human clock gene while studying a rare inherited disorder. When mutated, the gene transforms individuals into extreme early birds, rising as early as 4:00 am. This discovery has urged scientists to better understand the genetic basis of the human circadian clock.