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Circadian Rytyhymys. Your body has more than 100 circadian rhythms. Each unique 24-hour cycle influences an aspect of your body's function, including body temperature, hormone levels, heart rate, blood pressure-- even pain threshold. How your body keeps time.
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Your body has more than 100 circadian rhythms. Each unique 24-hour cycle influences an aspect of your body's function, including body temperature, hormone levels, heart rate, blood pressure-- even pain threshold.
How your body keeps time • In your brain is a type of "pacemaker" called the suprachiasmatic (soo-prah-ki-az-MAT-ik) nuclei. This area of your brain regulates the firing of nerve cells that seem to set your circadian rhythms. • Scientists can't explain precisely how this area in your brain "keeps time." They do know your brain relies on outside influences, "zeitgebers" (ZITE-ga-berz), to keep it on a 24-hour schedule. • The most obvious zeitgeber is daylight. When daylight hits your eyes, cells in the retinas signal your brain. Other zeitgebers are sleep, social contact and even regular meal times. They all send "timekeeping" clues to your brain, helping keep your circadian rhythms running according to schedule.
Almost no area of your body is unaffected by circadian rhythms. • Sleep and wake--It may seem you sleep when you're tired and wake when you're rested. But your sleep patterns follow a circadian rhythm. • You're most likely to sleep soundly when your temperature is lowest, in the wee hours of the morning. You're also most likely to awaken when your temperature starts to rise around 6 to 8 a.m. • As you age, your brain's "pacemaker" loses cells. This changes your circadian rhythms, especially noticeable in how you sleep. You may nap more, have disrupted sleep and awaken earlier.
Temperature -Your temperature is lowest when you're inactive. • Despite these factors, temperature follows a definite circadian rhythm. • In late afternoon, your temperature can be as much as 3 º C higher than in the morning. • Hormone production - Almost all hormones are regulated, to some extent, by circadian rhythms. • Cortisol affects metabolism and regulation of your immune system. • Its levels are highest between 6 and 8 a.m. gradually declining throughout the day. • If you change your daily sleeping schedule, the peak of cortisol's cycle changes accordingly. • Growth hormone stimulates growth in children and maintains muscle and connective tissue in adults. Sleep triggers hormone production, regardless of when you go to bed. • Production peaks during the first two hours of sleep. • If you're sleep deprived, production drops.
Cardiovascular system -More strokes and heart attacks occur in the morning than at any other time of day. • Experts contend morning changes in your body -not exercise - may be responsible for cardiovascular problems. • Blood clots most rapidly at about 8 a.m. • Blood pressure also rises in the morning and stays elevated until late afternoon. It drops off and hits its lowest point during the night. • These changes occur independently of physical activity. Exercise at any time of the day is beneficial. • On the other hand, if you're training for athletic competition, you may have reason to schedule that event later in the day. • Athletes seem to perform best in the late afternoon, when strength, body temperature and flexibility peak.
Pain tolerance Athletes who compete late in the day may perform better because they can "gain" without as much "pain." Pain tolerance is highest in the afternoon. One study shows tooth pain is lowest in the late afternoon, a consideration when you schedule your next dental appointment. • MedicationScientists are looking at how circadian rhythms affect the way your body uses medications. One finding is that less anaesthesia is needed to cause analgesia or drowsiness when administered in the afternoon. • Stay on scheduleChanges in daily habits such as a short night's sleep can disrupt your circadian rhythms. You may be able to stay "in sync" by keeping a consistent daily schedule.
What is Time Zone Change Syndrome?Time zone change (jet lag) syndrome consists of varying degrees of difficulties in initiating or maintaining sleep, excessive sleepiness, decrements in subjective daytime alertness and performance, and somatic symptoms (largely related to gastrointestinal function) following rapid travel across multiple time zones. • What are the symptoms?The symptoms begin within 1 or 2 days after air travel across at least 2 time zones. A discernable disruption of the normal circadian sleep-wake cycle is present. Insomnia Excessive sleepiness Decreased daytime performance Tired muscles Headaches Moodiness Altered appetite Stomach problems Increase in the frequency of nocturnal awakening to urinate