Part 5: What are Circadian Rhythms

    Part 1: What are Circadian Rhythms

    ‘Circadian rhythms’ is a Latin term, meaning “around a day” – and is a modern medical term which describes the regular changes to our bodies that occur within our mental and physical characteristics during the course of a day. Typically, circadian rhythms are controlled by your body's internal "clock." Called the suprachiasmatic nucleus or SCN, this clock is actually two brain structures, each around the size of the head of a pin, and each contains about 20,000 neurons. The SCN is in an area of the brain called the hypothalamus, just above the location where the optic nerves cross each other. When light reaches sensors, called the photoreceptors, in the retina, it creates signals that travel through the optic nerve to the SCN.


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    Signals from the SCN then travel to multiple brain regions, including once called the pineal gland, which reacts to light-induced signals by switching off production of the hormone melatonin, which is associated with the onset of sleep. The body's level of melatonin usually rises after sunset, making you feel sleepy. The SCN also controls actions that are synchronized with the sleep/wake cycle. These include hormone secretion, urine production, temperature, and changes in blood pressure.

    By eliminating light and other external time cues, scientists have learned that most people's internal clocks work on a 25-hour cycle instead of the standard 24-hour one. Because sunlight or other bright lights can reset the SCN, our internal cycles normally follow the 24-hour cycle, which is determined by the sun, rather than our natural cycle. Circadian rhythms can be affected somewhat by almost virtually any kind of external time indicator, such as your alarm clock, the local school bell, or even the timing of your dinner. The scientific name for such external time cues is zeitgebers, which is German for "time givers".

    When people move from one time zone to another, they tend to suffer from a very common form of altered circadian rhythms - otherwise known as jet lag. For example, if you fly from California to New York, you lose 3 hours, according to your body's internal clock. Because of this change, you will most likely feel tired when your alarm clock alarm rings at 8 a.m. the next morning because, according to your body's clock, it is still 5 a.m. It usually takes a few days for your body to adjust to the new time zone.

    To reduce the effects of jet lag, some doctors try to manipulate the internal clock with a method called light therapy. They expose people to special lights, which are much brighter than ordinary household light, for several hours near the time the patient wants to wake up. This helps them reset their internal clocks and adjust to the new time zone.

    Symptoms similar to jet lag are very common in people who work nights or rotating shifts. Because their work schedules are constantly conflicting with strong sleep-regulating reminders such as sunlight, they often become very drowsy during work, and may suffer insomnia or other problems when they do try to sleep. Shift workers also show an increased risk of cardiac related issues, digestive system problems, as well as emotional problems. All of these may well be related to their sleeping problems.

    The frequency and degree of workplace accidents also shows a tendency to increase during the night shift. Major industrial accidents linked at least partly to mistakes made by sleep deprived night-shift workers include the Three Mile Island and Chernobyl nuclear power plant accidents, and the Exxon Valdez oil spill. A recent study found that medical interns on the night shift are two times as likely to misinterpret test results, which could put their patients at risk. It may be possible to reduce shift-related fatigue by using bright lights in the workplace, minimizing shift changes, and taking scheduled naps.

    Some people who suffer from total blindness have life-long sleep issues due to the inability of their retinas to detect light, which causes a kind of permanent jet lag and occasional insomnia due to the fact that their circadian rhythms run concurrent with their actual cycle rather than a typical 24-hour one. It presents a difficult quandary, to be sure.

    Doctors say that daily supplements of melatonin could improve sleep for such patients; however, because of the high doses of melatonin found in most over-the-counter supplements, there can be a build up in the body, thus long-term use of this substance could possibly create other problems. The potential side effects of melatonin supplements are still largely unknown, so most experts don’t suggest melatonin use by the general public.

    If you are a person experiencing problems with your sleep cycle, either due to work related scheduling, excessive travel or other factors, there are some step you can take to attempt to minimize the effect. First, consult with your doctor, and if necessary, participate in a sleep study to see if there are any sleep disorders that may be responsible for the problem. Many such disorders are treatable.

    Also make certain your sleep environment is optimized for comfort. Ensure that the area is dark, cool and quiet. Try and keep all pets out of the area, as pet dander can cause allergies which can disturb sleep patterns. Such allergies can also be triggered by dust mites, allergens and bio-fluids introduced into the mattress by natural means. The American Sleep Association suggests SecureSleep™ encasement, an effective anti-bed bug/dust mite mattress and pillow cover.

    (Sources: American Sleep Association, National Institute of Neurological Disorders and Stroke, The National Institutes for Health and Bedbug.com)

    This informative series of sleep articles is brought to you by SecureSleep™, the bedding encasement specialists, insuring that you can go to sleep with the piece of mind knowing you are protected from bed bugs and allergens. SecureSleep™ promotes Sleep Hygiene and Health. We are proudly endorsed by the American Sleep Association who recommends using SecureSleep™ encasements, an effective anti-bed bug/dust mite mattress and pillow cover.

    Related Articles

    Part 1: Sleep Basics - Why Do We Need Sleep

    Part 2: How Much Sleep is Enough Sleep

    Part 3: What are the Benefits of Sleep

    Part 4: Importance of REM Stage Sleep and Dreaming

    Part 5: What are Circadian Rhythms (this article)

    Part 6: Disease Associated with Sleep

    Part 7: Sleep Disorders

    Part 8: Clean Sleep Environment