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Untangling the Mystery of Biological clock

Health, Sleep

Untangling the Mystery of Biological clock


Centuries before the first mechanical clock was invented, our ancestors used to rely on the sun as the most reliable source to keep track of time. the master clockLikewise, our bodies evolved an internal clock to synchronize itself with the hours of the sun.

This body clock is found in most living organisms, animals, plants and micro-organisms alike.

Scientists name it as the biological clock. This clock regulates the sleep-wake cycle through the body’s internal rhythm, called the circadian rhythm.[1] The term circadian comes from the Latin words, ‘circa’ (about) and diem (a day) which means it follows a roughly 24 hour cycle like the earth’s.

The circadian rhythm includes physical, mental and behavioral changes in our body and synchronizes our performance throughout the day till we doze off to sleep and even during sleep and the next morning again. The cycle goes on.

However, modern day stress has began to disturb our biological clock, and this can have serious health effects. So, knowing a little more about the biological clock and what all contributes to this process will enable us to keep it on track. To make it simpler, I’ll begin with the basics.

What controls the biological clock?

The biological clock, that controls the circadian rhythm, is actually made up of a number of interacting molecules in our body cells. This clock is controlled by a master clock, which keeps our bodily functions in sync.

The master clock consists of a cluster of around 10,000 nerve cells called the suprachiasmatic nucleus, or SCN that reside deep within a part of our brain called hypothalamus.

Located above a major junction of nerves coming from the eyes, the SCN regulates all body processes starting from our sleep-wake cycle, body temperature and metabolism, to other basic body maintenance like cell division and bone growth. Hence, the master clock.

Untangling the Mystery of the Biological Clock

How does the clock work?

Our biological clock is affected by both internal and external factors. Internal factors include numerous genes that regulate body processes like physical and mental alertness, hunger and mood. Chemicals and proteins produced by the body also fluctuate this process. Externally, our body receives cues from the environment to remain in the 24 hour cycle. This includes light and darkness.

Like I said, the SCN is located above the optic nerves, which relay incoming information from the eyes to the brain. When there is sunlight, our brain receives signals from the optic nerves to wake up and and become active.

Sunlight keeps our body in high gear and as night falls, our body processes return to the lowest level.[2] The brain, then indicates our body to produce more melatonin, the sleep hormone to prepare the body for sleep.[3] Okay, the basics made clear, let me resolve some ongoing debates surrounding our body clock mechanism.

Does genes influence us to become a morning or a night person?

With discussions on whether genes have an influence on us as a morning or an evening person, a recent study by Neurogeneticist Dr Louis Ptacek, published in 2014, established that genes can direct our circadian rhythm. He identified families with Familial Advanced Sleep Phase syndrome and found a certain gene mutation which resulted in advanced sleep and wake hours in the family.[4]

Difference in speed of the circadian rhythm may also influence your sleep pattern. If your cycle speed is a little ahead than 24 hours,  you are likely to be an early riser and if your clock runs slightly slower than 24 hours, you tend to be an owl. Its regulation is affected by both genetic factors as well as input of light.

Researchers also say that, the circadian rhythm may alter with age.  The deterioration of circadian rhythms in the elderly may result in sleep disturbances and reduced daytime function.[5]

How does it affect your health?

stressSince your biological clock follows the 24 hour cycle, interfering with it might affect your health adversely. Those who follow an irregular routine or have night shift jobs, experience delayed or insufficient sleep and feel less active during day hours.

Studies claim that disrupting your biological clock for days increases your risk to several illness including type 2 diabetes, obesity and heart disease.[6]

Orfeu Buxton, a Phd and a neuroscientist, conducted a study where he put healthy adults on sleep restriction to 5.6 hours of sleep for 3 weeks. The result was increased blood sugar level and decreased metabolic rate in the subjects which raised the chances of obesity and type 2 diabetes.[7]

Is eight hours of sleep the Universal rule?

Doctors and scientists keep weighing the accurate number of hours needed for a person to work productively. The most common answer being the number 8. But, there couldn’t be one number for all of us.

The best way to identify how many hours of sleep your body needs is by optimizing your sleep time. An easy way to find that out is to sleep through few consecutive Sundays. If you wake up fresh without an alarm regularly around the same time, then those hours should be sufficient for you.

It is also possible to feel drowsy in the afternoon, as your body functions become slower during that time. A nap of around 20-30 minutes should be good enough to get back to work again.

Maintaining odds with our biological clock is not a healthy habit, and in modern times, there can be plenty of factors that can lead to its disturbance. However, as much as our daily routine demands sticking to odd hours, paying heed to one’s internal clock is crucial in order to lead a healthier lifestyle.

Read Tips to Sleep Better  to get your clock  back in sync.


[1] Panda, S., Hogenesch, J., & Kay, S. (2002). Circadian rhythms from flies to human Nature, 417 (6886), 329-335 DOI: 10.1038/417329a. ^Back to Top^

[2] Wurtman RJ (1975). The effects of light on the human body. Scientific American, 233 (1), 69-77 PMID: 1145170. ^Back to Top^

[3]Reiter, R. (1991). Melatonin: The chemical expression of darkness Molecular and Cellular Endocrinology, 79 (1-3) DOI: 10.1016/0303-7207(91)90087-9. ^Back to Top^

[4]Xu, Y., Padiath, Q., Shapiro, R., Jones, C., Wu, S., Saigoh, N., Saigoh, K., Ptáček, L., & Fu, Y. (2005). Functional consequences of a CKIδ mutation causing familial advanced sleep phase syndrome Nature, 434 (7033), 640-644 DOI: 10.1038/nature03453. ^Back to Top^

[5]Schmidt, C., Peigneux, P., & Cajochen, C. (2012). Age-Related Changes in Sleep and Circadian Rhythms: Impact on Cognitive Performance and Underlying Neuroanatomical Networks Frontiers in Neurology, 3 DOI: 10.3389/fneur.2012.00118. ^Back to Top^

[6]Prasai, M., George, J., & Scott, E. (2008). Molecular clocks, type 2 diabetes and cardiovascular disease Diabetes & vascular disease research : official journal of the International Society of Diabetes and Vascular Disease, 5 (2) DOI: 10.3132/dvdr.2008.015. ^Back to Top^

[7]Buxton, O., Cain, S., O'Connor, S., Porter, J., Duffy, J., Wang, W., Czeisler, C., & Shea, S. (2012). Adverse Metabolic Consequences in Humans of Prolonged Sleep Restriction Combined with Circadian Disruption Science Translational Medicine, 4 (129), 129-129 DOI: 10.1126/scitranslmed.3003200. ^Back to Top^

Last Updated: August 12th, 2014
Next Scheduled Update: October 12th, 2014

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