Body Clock

The body clock comprises organisms’ natural timing devices that regulate the cycle of circadian rhythms. This is an internal mechanism that periodically schedules the body’s activities and functions.

What Is Body Clock?

The internal body clock is the body’s natural timing mechanism that regulates certain important biological functions and activities in every living organism.

The body clock is also known as the circadian rhythm [mfn] Farhud, D., & Aryan, Z. (2018). Circadian Rhythm, Lifestyle and Health: A Narrative Review. Iranian journal of public health, 47(8), 1068–1076. [/mfn]; it involves the 24-hour internal clock in our brain that regulates cycles of alertness and sleepiness by responding to changes [mfn] Reddy, S., Reddy, V., & Sharma, S. (2022). Physiology, Circadian Rhythm. In StatPearls. StatPearls Publishing. Available from: https://www.ncbi.nlm.nih.gov/books/NBK519507/ [/mfn] in light and the environments around us.

An example of a light-related circadian rhythm is sleeping at night and remaining awake during the day. This rhythmic body clock also controls the body’s metabolism, blood pressure, sleep cycle, and hormonal system.

How Does The Body Clock Work?

This body clock is also characterized by homeostasis [mfn] Cells, the fundamental units of life, exchange nutrients and wastes with their surroundings: Chapter 1 Homeostasis: A framework for human physiology. (n.d.). Retrieved December 1, 2022, from http://www5.zzu.edu.cn/__local/6/11/11/2ED0C021F8D2A94F378742685EC_422338ED_2BD652.pdf [/mfn]. Homeostasis is the process by which every living organism actively maintains stable conditions for survival. It is related to the pineal gland, the prime center of the body’s internal clock that regulates circadian rhythms.

The gland receives information about the daily light-dark (day-night) cycle from the retinas and accordingly modulates the secretion of melatonin.

A greater amount of melatonin is secreted when it’s dark, thereby pointing to melatonin’s role in sleep. In fact, melatonin is the key hormone in the coordination between the circadian system and circadian rhythm.

However, other hormones (like vasopressin, acetylcholine, insulin, and leptin) and body temperature also influence the workings of the body clock.

Our body clock helps to regulate internal cycles that perform important physiological functions, metabolism, and behavior. It enables all living creatures to anticipate and understand the rotation of the Earth within the timeframe of 24 hours.

In mammals, influenced by the light/dark cycle, the circadian clock optimizes metabolism and energy harvesting. The sleep-wake cycle [mfn] Reddy, S., Reddy, V., & Sharma, S. (2022). Physiology, Circadian Rhythm. In StatPearls. StatPearls Publishing. Available from: https://www.ncbi.nlm.nih.gov/books/NBK519507/ [/mfn] is one of the most important circadian rhythms, synchronized as it is by a master clock in the brain.

Master clock

Some environmental cues, especially daylight [mfn] Blume, C., Garbazza, C., & Spitschan, M. (2019). Effects of light on human circadian rhythms, sleep and mood. Somnologie : Schlafforschung und Schlafmedizin = Somnology : sleep research and sleep medicine, 23(3), 147–156. https://doi.org/10.1007/s11818-019-00215-x [/mfn], directly influence the master clock. It is a clock in the brain that coordinates all the other biological clocks in a living being’s body.

In vertebrate animals [mfn] National Institute of General Medical Sciences. (n.d.). National Institute of General Medical Sciences (NIGMS). Retrieved December 1, 2022, from https://nigms.nih.gov/education/fact-sheets/Pages/circadian-rhythms.aspx#201 [/mfn], including humans, it is a group of about 20,000 neurons [mfn] National Institute of General Medical Sciences. (n.d.). National Institute of General Medical Sciences (NIGMS). Retrieved December 1, 2022, from https://nigms.nih.gov/education/fact-sheets/Pages/circadian-rhythms.aspx#19 [/mfn] that form a structure called the suprachiasmatic nucleus (SCN). Situated in the hypothalamus of the brain, it receives direct input from the eyes. That’s why the day and light cycle is tied to the circadian rhythm.

What Affects The Circadian Rhythm?

The biological clock is influenced by certain behavioral patterns and external stimuli. This clock influences some core activities of the body, including:

1. Metabolism

The internal body clock and food intake are directly related to metabolism [mfn] Froy O. (2011). The circadian clock and metabolism. Clinical science (London, England : 1979), 120(2), 65–72. https://doi.org/10.1042/CS20100327 [/mfn], as it is the only factor responsible for energy production.

2. Sleep

The body clock controls the sleep-wake cycle, with light being the main external stimulus that influences the rhythm.

3. Age

Aging [mfn] Duffy, J. F., Zitting, K. M., & Chinoy, E. D. (2015). Aging and Circadian Rhythms. Sleep medicine clinics, 10(4), 423–434. https://doi.org/10.1016/j.jsmc.2015.08.002 [/mfn] is also associated with the body clock. In fact, due to old age, elderly people experience difficulties in completing basic day-to-day activities linked to energy production and sleep.

4. Food

For synchronizing circadian rhythms, food is considered the main stimulus. This clock regulates cellular differentiations and the cell cycle. However, the process is yet to be understood well.

5. Immune response

It has been observed in research that body clock affects the immune system responsible for the change in response to bacterial infection. In particular, specialized cells called macrophages, which are big cells that engulf and kill bacteria.

6. Physical and psychological disorientation

Sometimes traveling may cause physical and mental exhaustion. Such a condition disrupts the body clock.

Causes Of Circadian Rhythm Disruptions

Circadian rhythm disruptions and, in more severe cases, body clock disorders may set in for a variety of reasons. These include:

1. Shift work

Lifestyle patterns, especially shift work [mfn] Wickwire, E. M., Geiger-Brown, J., Scharf, S. M., & Drake, C. L. (2017). Shift Work and Shift Work Sleep Disorder: Clinical and Organizational Perspectives. Chest, 151(5), 1156–1172. https://doi.org/10.1016/j.chest.2016.12.007 [/mfn], can trigger circadian rhythm disorders. Several studies attest that constant or recurrent patterns of sleep interruption results in insomnia or excessive sleepiness.

Most night shift workers experience difficult sleeping patterns and disturbances in their bodily functioning. This can also trigger metabolic changes and severe changes in weight and mood.

2. Jet lag

When people travel across multiple time zones, they frequently face difficulties in adjusting to new schedules due to jet lag. Attributed to a brief disruption in the internal body clock, jet lag makes people experience brain fog, sleeping problems, and disoriented feelings.

3. Delayed sleep disorder

Delayed sleep disorder syndrome [mfn] Nesbitt A. D. (2018). Delayed sleep-wake phase disorder. Journal of thoracic disease, 10(Suppl 1), S103–S111. https://doi.org/10.21037/jtd.2018.01.11 [/mfn] is a type of circadian rhythm disorder commonly prevalent in people who have a habit of staying awake into the late hours of the night and waking later in the morning. Mostly the younger generations, who are comfortable addressing themselves as ‘night owls”, experience its symptoms.

Read More About Sleep Disorders Here

4. Effect of drug and alcohol intake

Certain drugs and alcoholic drinks [mfn] Roehrs, T. A., & Roth, T. (2015). Sleep Disturbance in Substance Use Disorders. The Psychiatric clinics of North America, 38(4), 793–803. https://doi.org/10.1016/j.psc.2015.07.008 [/mfn] cause circadian rhythm disruptions, even inducing sleep disorders. Consuming alcohol during the evenings may cause unnecessary sleepiness, whereas consuming it late at night may cause sleep disruptions throughout the night. Other substance intakes (like narcotics) can also disrupt our body clock and mental health.

Read More About Alcoholism And Mental Health Here

5. Irregular sleep-wake disorder

People who are in the habit of taking short naps throughout the day or those with no proper sleeping pattern may experience body clock disorders, particularly irregular sleep-wake disorder.

Moreover, people with neurological conditions (such as dementia), children with intellectual disabilities, and people with traumatic brain injuries may also experience disruptions in the body clock.

Circadian Rhythm Disruption And Physical Health

Circadian rhythm disruptions can trigger certain physical health symptoms linked to:

• Reduced life expectancy
• Increased risk of cancer
• Cardiovascular diseases (like stroke and heart attack)
• Obesity
• Metabolic syndromes

Read More About Obesity Here

Circadian Rhythm Disruption And Mental Health

Circadian rhythm disruption affects mental health—triggering severe mental health conditions like:

• Irritability
• Decision-making problems
• Depressive disorders [Read more]
• Mood disorders [Read more]
• Sleep disturbances
• Decreased alertness
• Cognitive impairment (memory disorders like dementia, Parkinson’s disease, etc.).

Read More About Dementia Here

How To Maintain A Healthy Body Clock

The focus of the treatment of body clock disorders is to reset a disrupted circadian system and reinstate a healthy sleep-wake cycle. Specialists generally chalk out treatment plans depending on the severity of the problems experienced and the type of body clock disorder.

1. Bright light therapy

In this type of therapy, the patient is advised to plan a particular time daily to sit in front of a lightbox. The lightbox will provide a variety of bright lights, such as sunlight. Light visors and light glasses are generally used in this therapy. Bright light therapy [mfn] Zhu, L., & Zee, P. C. (2012). Circadian rhythm sleep disorders. Neurologic clinics, 30(4), 1167–1191. https://doi.org/10.1016/j.ncl.2012.08.011 [/mfn] adjusts the amount of melatonin the body makes and resets the sleep cycle.

2. Melatonin supplement

Melatonin supplements [mfn] Tordjman, S., Chokron, S., Delorme, R., Charrier, A., Bellissant, E., Jaafari, N., & Fougerou, C. (2017). Melatonin: Pharmacology, Functions and Therapeutic Benefits. Current neuropharmacology, 15(3), 434–443. https://doi.org/10.2174/1570159X14666161228122115 [/mfn] are generally prescribed to treat delayed sleep disorders, irregular sleep cycles, etc.

3. Healthy lifestyle changes

A healthy lifestyle [mfn] Farhud, D., & Aryan, Z. (2018). Circadian Rhythm, Lifestyle and Health: A Narrative Review. Iranian journal of public health, 47(8), 1068–1076. [/mfn] helps in reducing circadian rhythm disorder symptoms and, therefore, experts suggest patients follow a well-planned daily routine. This routine may include a scheduled meal time, a good sleep hygiene regime, adequate exercise, limited intake of caffeine and alcohol, etc.

Takeaway

A healthy body clock is central to our sound mental and physical well-being as well as everyday functioning. Therefore it is important to listen to your body clock and maintain it well. Due to hectic schedules and disruptive lifestyles, it may not be always possible to stick to habits that ensure a sound circadian rhythm.

It also takes time and effort to reset a disoriented body clock and, in the process, everyday functioning. However, it is assured that the changed lifestyle will lead to improved motivation and greater productivity.

At A Glance

1. The body clock is an internal mechanism that periodically schedules the body’s activities and functions in living beings.
2. It is also known as the circadian rhythm.
3. It controls metabolism, blood pressure, sleep cycle, and hormonal secretions.
4. It coordinates physiological and behavioral activities, matching with environmental variations.
5. Disruptions in the body clock can lead to several mental and physical health conditions.
6. Circadian rhythm disruptions and disorders can be easily addressed with light therapy, pharmacotherapy, and self-help coping strategies.

Frequently Asked Questions (FAQs)