Are you sleepy sometimes in the afternoon? Do you seem to handle
physical tasks more easily late in the day? If so, you already know
about circadian rhythms.
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. Understanding how these cycles interplay is fascinating. And,
in some cases, you may be able to plan your day to take advantage of
your body's natural rhythms.
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.
Rhythms control your day
Almost no area of your body is unaffected by circadian rhythms.
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.
Body Rhythms