Biological Clock Sleep or Circadian Rhythm with examples

Biological Clock Sleep or Circadian Rhythm is an important role in daily life. The circadian or circadian rhythm, also known as the “biological clock”. Biological clocks are internal timing devices that are genetically set to regulate various physiological responses for different periods of time.  


Circadian rhythm refers to a  biological clock that is genetically programmed to regulate physiological responses within a  time period of  24  hours (about one day).

        THE  SUPRACHIASMATIC  NUCLEUS  is one of many groups of cells that make up the hypothalamus, which lies in the lower middle of the brain. The suprachiasmatic nucleus is a sophisticated biological clock that regulates a number of circadian rhythms, including the sleep-wake cycle.  Because this nucleus receives direct input from the eyes,  the suprachiasmatic cells are highly responsive to changes in light.

         Light regulates sleep-wake circadian rhythms,  the absence of light should disrupt circadian rhythms in blind people and cause sleep problems.  Researchers found that many blind people do report sleep problems  (Lamberg,  2006;  Murano,  2006).  

        Besides the  24-hour  sleep-wake circadian clock,  you also have other clocks in your brain,  including one that measures shorter periods of time,  called an interval timing clock (Buhusi & Meck, 2005).  

Read more article : Sleep: Sleep Stages, REM Sleep, Biological, and Circadian Rhythms

THE  INTERVAL  TIMING  CLOCK,  which can be started and stopped like a  stopwatch, gauges the passage of seconds,  minutes,  or hours and helps people and animals time their movements,  such as knowing when to start or stop doing some activity  (taking a  one-hour nap and actually waking up about an hour later).  The interval timing clock is located in a part of the brain known as the basal ganglia.


Another clock in your brain is regulated by food.

THE  FOOD-ENTRAINABLE  CIRCADIAN  CLOCK (also referred to as the midnight-snack clock) regulates eating patterns in people and animals and might be responsible for late-night eating in people. Thus,  obese people,  many of whom eat more than half their calories at night,  may have an abnormality in their clock,  which is located in the hypothalamus (C. Brownlee, 2006b; Maeda et al., 2006).


 Biological Clock OR Circadian Problems and Treatments :


SHIFT WORKERS and late-night drivers have more accidents are their sleep-wake clocks have prepared their bodies for sleep, which means they feel sleepy, are less attentive and alert, and are often in a lousy mood (Ohayon et al., 2002). Frequent major changes in working hours will likely cause much stress on the body and brain (Aamodt & Wang, 2008).


JET LAG is the experience of fatigue, lack of concentration, and reduced cognitive skills that occurs when travelers’ biological circadian clocks are out of step or synchrony with the external clock times at their new locations.

     severe jet lag can be for flight attendants who frequently make long trips. those who do not take breaks to allow their circadian clocks to readjust experience impaired cognitive skills (Aamodt & Wang, 2008). After 3 months in space, astronauts experience “space lag” or sleeplessness because their circadian clocks are not being reset (Monk et al., 2001).


RESETTING CLOCK: Researcher Charles Czeisler (1994) spent ten years convincing his colleagues that light could reset circadian clocks. After he finally succeeded, other researchers used his and their own research to obtain patents for light therapy (Nowak, 1994).

    Light therapy is the use of bright artificial light to reset circadian clocks and to combat insomnia and drowsiness that plague shift workers and jet-lag sufferers.  It also helps people with sleeping disorders in which the body fails to stay in time with the external environment. For example, researchers report that workers who had been exposed to bright light and then shifted to night work showed improvement in alertness, performance, and job satisfaction (Czeisler et al., 1995). Exposure to bright light (about 20 times brighter) at certain times reset the workers’ suprachiasmatic nucleus and resulted in a closer match between their internal circadian clocks and their external shied clock times. Light therapy has enormous potential for resetting our sleep-wake clocks, and more recently it has been used to treat depression (B. Bower, 2005; Tompkins, 2003a, 2003b).


MELATONIN is a hormone that is secreted by the pineal gland,  an oval-shaped group of cells that is located in the center of the human brain. Melatonin secretion increases with darkness and decreases with light. The suprachiasmatic nucleus regulates the secretion of melatonin, which plays a role in the regulation of circadian rhythms and in promoting sleep.

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