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Tick, tock, says the clock
THERE are clocks all around us, keeping track of every second of our personal and professional lives, making us realize that there is no way recovering or making up for lost time. While digital and analogue clocks help us plan our lives, there is another kind of clock, stashed inside us, ticking away ever so silently, taking note of discreet changes in our body.
Commonly known as biological clocks, they are the invisible, intangible time trackers of our bodies. They have their internal timing mechanisms.
These internal clocks are also called the Circadian System that literally means “about a day.” Many questions like reasons for extreme exhaustion, animal hibernation in unfavourable environmental conditions, the lifting and lowering of leaves by plants at specific times, particular sleeping and waking times, aging etc., can be answered by understanding the relationship of biological clocks to living organisms.
A biological clock provides an automatic internal “watch” for organisms, even in the absence of apparent environmental signals like light. These clocks are involved in various bodily functions, as it drives our circadian rhythms (occurring about once per day) which are present in every living organism be it humans, animals or plants. They work all the time in the living body, alerting one’s system whenever it is needed. In the human body the circadian rhythm of biological clock controls our daily working capabilities, mood swings, sleep patterns, daily routine, metabolic rate, body temperature, blood pressure and hormone levels.
Early studies show that the biological clock is controlled by the Timex centre of the brain located in Supra Chiasmatic Nucleus (SCN) acting as the body’s clock centre, found in an area of the brain called the hypothalamus. The hypothalamus regulates hormone levels and plays a role in regulating different emotions. Recent findings suggest that proteins known as cryptochromes, are also involved in detecting changes in light and setting the body’s clock. The biological clock is also regulated by the pineal gland as nerve fibers also take signals from SCN to the former, influencing hormones and other functions. The presence or absence of external light controls the working of this gland, synchronizing and coordinating biological processes in the body. This gland also produces a hormone called melatonin and can only be produced in the absence of light. Melatonin has a sedative or calming effect on the body as it helps to decrease the level of anxiety, fright disturbances and migraines. It also plays a role in the maintenance of the body’s immune system. The clock can be reset or synchronized to one’s bodily requirement with the modification of duration and light and dark sequence. In some insects and snails, biological clocks are usually found in the retina. In birds, they are located in the pineal gland or hypothalamus.
Synchronization between the biological clock and various bodily functions and their timing is maintained by light signals via the optic nerve. Researchers believe that the biological clock is linked to light-sensing cells called photoreceptors. This type of cell reacts to sunlight in ways that help synchronize the clock with the 24-hour day. Humans require sufficient daylight to coordinate their circadian and circannual rhythms. However, the role of light in influencing the life and biological clock in all living things is still being studied.
A research conducted on the reaction of animals when they are deprived of light showed that animals were able to distinguish between the seasons even without the help of light. This further confirmed that animals and humans possess a biological clock in their body, which helps them to keep the estimated time in the body even if there is an absence of external stimuli like sunlight.
One uses natural light to adjust one’s body clock according to the external environment. When this synchronization is disturbed or if one fails to reset our body’s clock timings with natural light, one experiences problems like hormonal imbalance, sleep disorders, lack of appetite (feeling of hunger), reproductive disorders and disturbed mood patterns. For example, a disease called SAD with symptoms of disturbed sleep patterns and appetite, weight disorders and depression occurs when there is lack of sufficient light.
Scientific research has proved that biological clock is controlled by specific genes in the body called PER. Those who have distorted or halted clock genes clock cells function in a negative feedback cycle. Any mutation in clock genes result in variation of the length of cycle with a disturbed daily rhythm and other symptoms of disturbed cycle such as sleeplessness etc. These clock genes have controlling and stabilizing effects on other genes’ activities but their exact mechanism of action remains vague.
It has been studied that when one pays no attention to the 24-hour light-dark cycle and keep irregular hours of work and rest, the body’s internal rhythms go haywire. People who work with rotating shifts are known to suffer from various medical conditions like heart disease, back pain, respiratory problems and even ulcers. They are also susceptible to loss of attentiveness, the ability to make choices or decisions, higher error rates and frequent sleep disorders. Other illnesses are also linked to circadian rhythms, for example, heart attacks occur more regularly in the morning while asthma attacks occur more frequently at night.
Another related phenomenon is jetlag, caused when one travels a lot and is caught between different time zones. Though this is by no means critical, it is often associated with an unbearable and disorienting condition, due to disturbing effects produced in the body’s internal clock. Thus, the balance between one’s internal biological clock and the external environmental cycle is upset. Light therapy is now being used widely and quite effectively for the treatment of this condition.
Continuous research and study of biological clocks has helped scientists around the world in understanding various aspects of the body such as:
1. The biological basis of behavior and actions of humans and other organisms.
2. An understanding of the mechanism and treatment of jetlag, insomnia and mental disorders.
3. Mechanisms of rhythmic heart rate changes and other characteristics that affect the diagnosis and treatment of many disorders, including fever, the body’s hormonal levels and high blood pressure.
4. The ability of animals to foresee and prepare for upcoming events of the year, like changes in the environment, such as weather change and unfavourable conditions which makes them hibernate. In animals and insects biological clocks provide cues for change in length of the day as a sign for reproduction, migration, molting, locomotive activities, body temperature variations and colour changes in sea species like fishes and crabs.
5. Allowing for relatively precise timings of the periods during the day when external environmental signals are unclear, for example, temperature and light.
6. An understanding of factors responsible for aging in humans.
7. The disturbance of circadian rhythm and its effects such as mania in people with bipolar disorders.
8. Maintaining daily and continuous internal body functions and their timings.
9. A reduction in the amount of urine accumulated at night so that there is a lesser chance of urination during the whole night.
10. An understanding of variations in sleep patterns, memory and mood changes.
It has been noted that where the biological clock runs at a faster pace in some people, they usually tend to sleep early in the evening but have difficulty in waking up in the morning. Humans are able to reset their biological clock according to the day-night cycle, which is why they sleep and get up at appropriate times. Without biological clocks, one would go to bed early and get up early with each passing day.
The biological clock and its relation to living beings remain as an interesting field of study. It will help us in knowing the demands of our body and routine fluctuations in our daily working habits and actions. So let us explore and reset one’s biological clocks in accordance with the rhythm of nature and gain understanding about us.
The writer
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