I studied today about circadian rhythm in physiology.
Do you know how long horse have a sleep a day?
They can do well with two hours sleep a day.
How about dolphin?
Because of lung breathing, dolphin can not fall asleep. But they have a short sleep by switching both right and left brain alternately. (What a clever system they have!)
About human being, it is a famous story that Napoleon had three hours sleep a day, and Einstein had 10 hours sleep a day. And surprisingly, even there are a record of 8.4 minutes sleeping two weeks on an average.
But, usually human have 6to8 hours sleep a day. It is important to get non-REM sleep to recover brain fatigue. (REM stands for "rapid eye movement". When eyes are moving quickly during sleep, brain works as busy as in daytime, instead of that, muscle can take a rest. Then, non-REM sleep is the opposite.)
And, almost all the global creatures (even bacteria!) have "biological clock", and there are a "circadian rhythm" which means a roughly-24-hour cycle. According to a experiment of squirrel, even after keeping a life in darkness for one month, the circadian rhythm lingers on. The rhythm keeps the time of changing rest and action, and control of body temperature and amount of hormone at the same pace.
In which part of the body is biological clock located? Ummm, I want to write about this in English but it needs tooooo specialistic term to explain. So, I'll give it up.
It was a main point of this article though. hahaha:p
