At the end of a day full of work, it is general for people that their eyelids start to feel heavy. Laziness takes over and we begin to yawn. We all know that we're tired at that time, but why people get tired?

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    $\begingroup$ I took the liberty to remove all personal references to yourself to avoid being flagged as personal medical question. Please feel free to revert my edit at any time if you wish. $\endgroup$ Commented Apr 21, 2015 at 10:40
  • $\begingroup$ Also in this question the regulation of sleep is quite well answered and in your case I'd look for the homeostatic regulation of sleep (that is the accumulation of adenosine in the brain due to the depletion of energy sources in neurons after a long period of wakefulness). biology.stackexchange.com/questions/28123/length-of-sleep-time/… $\endgroup$ Commented Apr 21, 2015 at 10:44
  • $\begingroup$ Muscle fatigue - google that $\endgroup$
    Commented May 28, 2015 at 6:34

1 Answer 1


It is yet to be discovered by scientists. But there is a new study that finds that brain cells called astrocytes supply the urge to sleep by releasing adenosine a chemical known to have sleep-inducing effects. The chemical accumulates in the brain during waking hours, eventually helping to stimulate the unique patterns of brain activity that occur during sleep.
You can find more about it in this link bellow


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