The Circadian Rhythm

Photo by Carl Barcelo on Unsplash

We have always a primary concern about our overall health. Physical fitness, mental toughness, emotional stability, and spiritual evolvement are four different quadrants. We strive through different approaches like gymnasiums, yoga, mindful meditations, and more to fight various ailments and disorders like depression, anxiety, and chronic pains. Along with the specific exercises, a healthy diet is also necessary. Proper rest and sunlight also play a vital role in health and fitness. Let us understand the concept of circadian rhythm for a good lifestyle.

It is important for us how we live during our lifespan, but it is meaningless to understand unless we know the biological rhythm of our body or the internal mechanism that controls the sleep-wake cycle that happens in us. The period is almost 24 hours and 09 minutes to 24 hours and 19 minutes. It is believed that women’s periods are significantly shorter (24.09 hours) than men’s (24.19 hours).

Circadian is derived from the Latin words circa, which means “around” (or “roughly”), and dim, which means “day.” Diurnal rhythms involve processes of 24-hour cycles; circadian rhythms ought not to be considered diurnal rhythms until they can be established as endogenous and therefore not environmental.

While circadian rhythms are endogenous, external cues named zeitgebers (German meaning “time givers”), such as temperature, light, and redox cycles, adapt them to the local setting. A circadian rhythm sleep disorder is a term used in clinical settings to describe an irregular circadian rhythm throughout humans.

According to the reviews of psychology today, Circadian rhythms are the cycles that tell the body when to sleep, wake, and eat — the biological and psychological processes that oscillate in predictable patterns each day. This internal clock is influenced by external cues, like sunlight and temperature, which help determine whether one feels energized or exhausted at different times of the day.

Circadian rhythms are governed by a master clock, a group of neurons called the suprachiasmatic nucleus, located in a region of the brain called the hypothalamus. This master clock translates cues from the environment into directives for the body. For example, receptors in the eyes detect darkness and pass that signal along to the suprachiasmatic nucleus, which then stimulates the production of melatonin, the hormone that causes sleepiness.

Circadian rhythms have been critical throughout evolution, allowing animals to prepare for upcoming changes to their environment. Today, research is charting the harms of a disrupted circadian rhythm, such as sleep disorders, obesity, diabetes, depression, and bipolar disorder — not to mention difficulties concentrating and staying productive.

Due to frequent travel and shift work, many people today experience disturbances to their circadian clock. These disruptions can lead to difficulty sleeping, difficulty staying awake during the day, or clinical insomnia. More rarely, individuals may develop circadian rhythm disorders such as Delayed Sleep Phase Syndrome or Advanced Sleep Phase Disorder.

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Endogenous Vs Exogenous Factors

A circadian rhythm, also known as a circadian cycle, is an internal mechanism of an organism and its reaction to its surroundings. This applies to plants and animals including humans. The endogenous free-running cycle of nocturnal animals i.e., active at night is comparatively small than that of diurnal animals. An external stimulus that is being used to entrain a rhythm is sensitive and gives hypnosis effects. Numerous organisms reside in a wide range of temperatures, and thermal energy variations can influence the kinetics of all molecular processes within their cells.

The biological activities of an animal like a human vary depending upon the sleeping patterns and feeding. Seasonal weather patterns, food availability, and temperature are good predators of behavior patterns and prolonged survival. Change in these patterns drastically affect the health of animals. For instance, one of the dogs which were brought from an extreme minus-degree climate and higher altitude could not survive in normal temperatures for more than a few weeks.

Animals, like humans, who are held in complete darkness for long periods develop a free-running rhythm. Based on whether the “day,” or endogenous time, is longer or shorter than 24 hours, the sleep cycle has been pushed back and forward each “day.”

Researchers from the University of Tromso[1] in Norway discovered that certain Arctic species have circadian cycles during the months when there are frequent sunrises and sunsets. Reindeer at 70 degrees north exhibited circadian cycles in the winter, autumn, and spring, though not in the summer, according to a report. Just in the autumn and spring did reindeer on Svalbard, at 78 degrees North, exhibit these rhythms.

Circadian Rhythm in Plants notices distinguished patterns of each plant what season it is and when it is supposed to bloom to maximize pollinator attraction. Leaf movement, germination, stomatal/gas exchange, development, photosynthetic activity, fragrance emission, and enzyme activity are just a few of the behaviors that display rhythms. Certain fruits grow naturally in a colder climate like apples. They do not grow in inadequate climates or exogenous factors that invariably affect the internal rhythms.

Circadian Rhythm in Humans

The biological clock of the human body: When separated from external factors including daylight and timekeeping, early studies into circadian patterns indicated that almost all people favored a day nearer to 25 hours.

Nevertheless, this study was flawed since the researchers were not shielded from artificial light. The scientists were unaware of the phase-delaying impact of indoor electric lights because the subjects weren’t exposed to time signals (such as clocks) or daylight.

Whenever the subjects stayed up, they could switch on the sun, and then when they tried to sleep, they could switch it off. The circadian process of the biological clock in humans was delayed by exposure to electric light throughout the evening. According to a more rigorous study published by Harvard University in 1999, the natural human rhythm is similar to 24 hours and 11 minutes, which is also nearer to the solar day.

A much newer analysis from 2010 found sex differences within the circadian cycle for men and women, with women’s periods being significantly shorter (24.09 hours) than men’s (24.19 hours).

Females in this study appeared to be awake faster than men and preferred morning tasks more than men, even though the biological mechanisms underlying such variations remain unclear.

Photo by Helena Lopes on Unsplash

Take Away

1. Reset your body clock by keeping a regular schedule and exposing yourself to natural light in the morning.

2. Decrease the brightness of screens at all times and keep screens out of the bedroom altogether. 3. Increase your exposure to sunlight and nature.

4. Incorporate more exercise into your day and maintain a routine.

[1] Source:

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Former aircraft engineer IAF, Retired Branch Manager SBI, Psychologist, Best Selling Author & Defence Recruitment Trainer