Difference Between Biological Clock and Circadian Rhythm

The key difference between biological clock and circadian rhythm is that biological clock is an organism’s innate timing device composed of specific molecules that interact with cells throughout the body, while the circadian rhythm is a physical, mental, and behavioral change that follows a daily cycle.

We feel sleepy at night, but we are energetic and stay awake throughout the daytime. The reason behind this is the circadian biological clock. The biological clock is our innate timing device, which is controlled by our brain. Circadian rhythm is a natural and internal process which repeats roughly every 24 hours. Circadian rhythm can influence the sleep/wake cycle. Every tissue and organ in our body operates according to biological clock and circadian rhythms. The circadian clock system is a vital regulatory factor for nearly all physiological activities in our body. Disorders in the circadian clock system can cause severe consequences for human health.

CONTENTS

1. Overview and Key Difference
2. What is Biological Clock
3. What is Circadian Rhythm
4. Similarities Between Biological Clock and Circadian Rhythm
5. Side by Side Comparison – Biological Clock vs Circadian Rhythm in Tabular Form
6. Summary

What is Biological Clock?

The biological clock is an innate timing device present in all organisms. It consists of specific molecules that interact with the cells of the body. Every tissue and organ has a biological clock. Biological clocks keep body processes running according to a schedule. Therefore, they are really important for the functioning of life and to the organization and coordination of behavior.

There are several different biological clocks in our body. Age and female fertility, circadian clock, circadian rhythm, menstrual cycle, molecular clock, epigenetic clock are several examples. Hence, biological clocks maintain the periodicity of biological functions occurring in our body.

What is Circadian Rhythm?

Circadian rhythm is a result of the circadian biological clock. It is a physical, mental or behavioral change occurring according to a 24 cycle. Basically, it is a 24-hour cycle which is endogenous. Many types of living organisms, including animals, plants, fungi, cyanobacteria and bacteria, are governed by circadian rhythms. Circadian clock primarily responds to light and dark. Hence, the circadian rhythm mainly regulates the sleep/wake cycle. It also influences hormone release, eating habits, digestion, body temperature and some other functions of the body. The study of the biological rhythms is the field called chronobiology.

Different factors affect biological rhythms. Exposure to sunlight, drugs and caffeine can affect sleep cycles. If anything disrupts the circadian rhythms, it affects our body function and health. Abnormal or disrupted rhythms are responsible for various health conditions such as sleep disorders, obesity, diabetes, depression, bipolar disorder, and seasonal affective disorder, etc.

What are the Similarities Between Biological Clock and Circadian Rhythm?

• Biological clocks generate circadian rhythms and regulate their timing.
• Changing the light-dark cycles can speed up, slow down, or reset biological clocks and circadian rhythms.
• Irregularly functioning biological clocks can result in disrupted or abnormal circadian rhythms.
• Both biological clocks and circadian rhythms are fundamental to the functioning of life.

What is the Difference Between Biological Clock and Circadian Rhythm?

The biological cycle is an innate timing device present in living organisms while the circadian rhythm is a 24-hour cycle that regulates physiological processes of living beings. So, this is the key difference between biological clock and circadian cycle.

Below infographic summarizes the difference between biological clock and circadian cycle.

Summary – Biological Clock vs Circadian Rhythm

Biological clock and circadian rhythms regulate the cycling of numerous functions in our body. The biological clock is a timing device that tissue and organ possess while circadian rhythm is a natural internal process that regulates our sleep/wake cycle every 24 hours. Therefore, circadian rhythm displays an oscillation of about 24 hours. Both biological clock and circadian rhythms are related to each other. In fact, the circadian rhythm is a result of the circadian biological clock. Thus, this is the summary of the difference between biological clock and circadian rhythm.

Reference:

1. “Circadian Rhythms”. Nigms.Nih.Gov, 2020, Available here.
2. “Circadian Rhythm”. En.Wikipedia.Org, 2020, Available here.

Image Courtesy:

1. “Biological clock human” By NoNameGYassineMrabetTalk✉ fixed by Addicted04 – The work was done with Inkscape by YassineMrabet. Informations were provided from “The Body Clock Guide to Better Health” by Michael Smolensky and Lynne Lamberg; Henry Holt and Company, Publishers (2000). Landscape was sampled from Open Clip Art Library (Ryan, Public domain). Vitruvian Man and the clock were sampled from Image:P human body.svg (GNU licence) and Image:Nuvola apps clock.png, respectively (CC BY-SA 3.0) via Commons Wikimedia
2. “Circadian rhythm” By Srruhh – Own work (CC BY-SA 4.0) via Commons Wikimedia