|MadSci Network: General Biology|
Why do we as humans, complex and intelligent mammals, get cold when we sleep? This question was answered through the many studies of sleep. As researchers studied "sleep", they were able to uncover many secrets of the human body and brain. Everyone knows that sleep is essential to rest and heal the body and mind. Basically the human being has two internal clocks that help regulate wakefulness and sleep: circadian rhythm and the body-temperature clock. The circadian rhythm, also known as the sleep clock, has been the most studied of the two biological clocks and found to be linked to the body-temperature clock. The circadian rhythm is influenced by the amount of light and darkness we experience during the day and provides the first signals to begin sleep. The body-temperature clock, however, is not influenced by external stimuli and is seen as the most primal of our internal clock. During the day, a healthy body's temperature only varies by about a degree or two Fahrenheit (half a degree or a degree Celcius). Interestingly, the low points of body temperature cycle correspond to "sleep gateways", times when it is easy for people to fall asleep. Typically the two lowest points of body temperature are in late afternoon (3-6 pm) and early morning (3-6 am) with the highest values commonly occurring in the evening (7:00 p.m. to 10:00 p.m.). Studies in which the body temperature has been monitored in a time-free environment have shown that our temperature level fluctuates in the same 25 to 26-hour pattern, no matter when we sleep or when we are awake. In short, our body temperature cycle operates independently of our sleep/wake cycle. The early morning period our body temperatures are much lower; thus why we may feel cold waking up some mornings. In the same way, the periods of highest body temperature are directly linked with an inability to go to sleep. By the way, studies have shown that exercise has no effect on the body temperature clock. The two clocks reinforce each other. The sleep clock generally tells the person to go to sleep just as his body temperature is starting its nightly decline. If the person ignores it, or has thrown off his sleep clock, the body temperature clock comes around and virtually forces him to go to sleep between 4 and 6 am. Then exposure to daylight when the person awakens resets the sleep clock. The documents this response is based and for any additional information on the physiology and anatomy of sleep can be found in the following resources: "How the Human Brain Developed and How the Human Mind Works" by Manfred Davidmann: http://www.solbaram.org/articles/humind.html "Circadian Rhythms - Critical Concepts" by Round-the-Clock-Systems: http://www.roundtheclocksystems.com/Workplace/Learning/sw.circadian.html "Frequently Asked Questions about Training Nutrition - Part Five - Self-assessment - Section 8" Version 6.6 (2/3/97)by Paul Moses: http://pages.prodigy.net/paolom/Docs/faq5.html#Sleep The Sleep Clinic: http://www.silentpartners.org/sleep/sinfo/index.htm The Sleep Medicine Home Page: http://www.users.cloud9.net/~thorpy/ The Natural Health School: http://www.naturalhealthschool.com/ The Brain Web: http://www.dana.org/brainweb/brainweb.cfm?CategoryID=17
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