The internal timing system that regulates natural cycles of our body and physiological processes over a period of about 24 hours is referred to as the Biological Clock.
This internal rhythm controls when a person feels awake or sleepy and influences many bodily functions, like hormone release, body temperature, metabolism, digestion and sleep patterns.
The Biological Clock operates through a natural process known as the Circadian Rhythm, which follows roughly a 24-hour cycle. This rhythm is primarily controlled by a small region in the brain called the suprachiasmatic nucleus. It receives signals from the eyes about light and darkness in the environment and adjusts the internal timing of the body accordingly.
One of the important glands involved in regulating the Biological Clock is the Pineal Gland. This gland secretes the hormone melatonin, which promotes sleep. When it becomes dark, melatonin production increases, making the body feel sleepy. In contrast, exposure to light reduces melatonin secretion, helping a person stay awake and alert.
The following are the primary conditions and factors that can cause the Biological Clock to malfunction or stop working effectively:
Lifestyle Disturbances
The most common causes of a “misfiring” Biological Clock are external factors that conflict with our natural internal timing.
Shift Work Disorder: Frequently working nights or rotating shifts forces the body to be active when the brain signals sleep. This chronic misalignment leads to long-term metabolic and cardiovascular problems.
Light Pollution: Exposure to blue light (from smartphones or bright indoor lighting) late at night suppresses melatonin, the hormone that signals sleep, effectively tricking the brain into thinking it is still daytime.
Delayed Sleep Phase Disorder (DSPD): It is a condition where the internal clock is shifted significantly later, e.g., falling asleep at 3:00 AM and waking at noon. This is frequently seen in adolescents and young adults these days.
Advanced Sleep Phase Disorder (ASPD): Conversely, the clock is shifted earlier e.g., falling asleep at 7:00 PM and waking at 3:00 AM, more common in the elderly.
Physiological and Pathological Triggers
The Biological Clock is sensitive to the internal chemistry of the body and cellular health.
Aging: As people age, the SCN may lose neurons or become less sensitive to light signals, leading to fragmented sleep and a “weakened” circadian signal.
Travelling to different time zones: Rapid travel across multiple time zones creates a conflict between the internal clock and the new local time. This results in fatigue, digestive issues and insomnia, usually known as jet lag, until the clock resets.
Neurodegenerative Diseases: Conditions like Alzheimer’s or Parkinson’s damage the SCN or the pathways that transmit light information, causing severe disruptions where patients may lose the distinction between day and night.
Blindness: Without light perception, the body loses its primary stimulus. While the internal clock still runs, it lacks the synchronization provided by the sun.
Extreme Environments
In environments where natural light-dark cycles are absent, the Biological Clock becomes “free-running.”
Polar Regions: During “Polar Night” (24-hour darkness) or “Midnight Sun” (24-hour daylight), the body can lose its sense of time without strict behavioural routines. In regions such as Scandinavia, Finland, Siberia and the Arctic territories of Canada and the U.S., the presence of the Midnight Sun and Polar Night necessitates a schedule based strictly on “clock time” rather than sun time”. This reliance on the clock helps residents maintain social and biological order despite the absence of traditional day-night cycles.
Space Travel: Astronauts experience 16 sunrises and sunsets a day on the International Space Station (ISS), which can completely scramble the circadian rhythm without artificial lighting protocols.
Consequences of a Malfunctioning Clock
When the biological clock stops performing its functions properly, the impact is systemic. It doesn’t just cause tiredness; it can lead to:
Increased obesity
Increased risk of diabetes
Mental health issues
Reduced ability to fight off infections
Difficulty with memory and focus
Difficulty in decision-making
Maintaining a stable Biological Clock, therefore, becomes important for good health. It can be supported by following regular sleep schedules, getting exposure to natural daylight, avoiding excessive screen light at night, exercising regularly and maintaining balanced daily routine.
The author is BDS, MPhil and Senior Instructor, Department of Biological & Biomedical Sciences, Aga Khan University, Karachi