why do people get tired?
486691
This is the best question I've ever seen.  Thanks so much for asking it!  You will not get the full answer, but it will be very interesting if you keep asking smart people what they think.  I really want to know the answer to this question, and I never thought to ask it myself.\n\nObviously the brain (and possibly the body as well) requires some kind of regenerative process, just like it requires a certain amount of food and water and oxygen.  You can't go too long without either, or else your body will break down.  If you "lose sleep," you suffer - no one gets away with it.  In fact, one of the ways they use to torture prisoners of war nowadays is sleep deprivation.  Even the most hardened killers begin to crack under its effects, physically and psychologically.  \n\nDo trees sleep?  You have to wonder.\n\nI'll let you in on one secret I know that most people do not.  One of the answers to your question is that the unconscious mind has about 1 million times more processing power than the conscious mind.  It would make sense if our body's natural functions require the full force of regulatory calculations that only the unconscious mind can perform.  In other words, if we only used our conscious minds to run our body and brains, we would quickly degenerate and die.  We're nowhere near as smart when awake as we are while asleep.  Unfortunately, the only way to do work (to get food & water) is to be awake, alert, receiving new data, and guiding one's movements.  Then again, we can live for decades in a coma.\n\nThis is such a great question.
872876
Maybe vitamins, caffeine, exercise, or even cutting back the night time sleep hours...too much sleep can also cause tiredness.
116477
Maybe he REALLY is tired. Ask him got to a doctor, he works too much (work-school) he might get mental and physically tired without noticing.
255946
temporarily it will make you feel sleepy because the body is trying to regain the lost energy by resting for a few minutes.
926902
b/c we are tired from a long day of a compbination of things. (work, school, working on car, having sex, etc.)
262962
It could be a poor diet, it could be a sign of disease... dehydration can make you feel sleepy, so drink at least one glass of water every hour...even if you don't feel thirsty, depression can also make a person feel sleepy. Or perhaps the person has lots of stress and worries and isn't really sleeping deeply. Exercise can really help you sleep well...I would suggest seeing a doctor first just to rule out any problems.. night ,night, sleep tight x
416315
You are getting very sleepy.
64411
when we sleep our brains dont shut down but slow down.  we rejuvinate our brain causing us to think more clearly and be more preductive in just about everything we do.  It can effect the body in the long run.  Our muscles dont get the proper rest they require.  here are two links.  the first goes into great detail about what it does to the brain and the second is sleep deprivation fron diccovery.com
248518
maybe you a. dont get enough sleep b. are anemic c. have a thyroid problem or d. suffer from depression e. many other reasons
1071612
Seriously, you could try having LESS sleep. Not many folks really require more than 8 hours a night on a regular basis once they are adults and before they hit old age. If I take more than that, I always get a headache.\n\nHowever, chronic fatigue can be caused by any number of things. An obvious cause could be an underactive Thyroid gland, for which there is a simple test which your doctor can arrange.
1021411
It really is not well known.  Physical exertion and mental stress bring on the feeling of fatigue.  We know the areas of the brain involved in sleep and wakefulness, but it is unclear whether tiredness results from an impaired ability for the blood to carry nutrients to the brain, or if the brain has a shut down mechanism to preserve muscles from overexertion.
305821
You yawn because there's not enough oxygen in the air and your body just does that to get more oxygen in one breath. So tecnicly everybody's not getting enough oxygen.
474251
Becuz since you don't feel sleepy at night ,, you try to stay up awake as much as you can,, so you fall asleep for a few hours then you have to go to work,, so you'll feel tired and sleepy becuz you didnt get enough sleep,, that's why you have to try sleeping earlier even tho you hate it,, so you'd have energy when you go to work :-)
419305
Oh wow, I get that all the time. Usually it is because you haven't had enough sleep, or because you are too tired. We do this out of protection, but it can be a very scary thing.
513192
Sounds like you need a really good medical check up...all kinds of ailments can make you tired all the time.You may even need a sleep study done.
1067556
its very possible...............the more you have the more tired you get
217186
In humans, and probably in all those organisms that yawn, yawning is caused by a lack of oxygen. When we are tired, we breathe less often as well as less deeply, so our bodies have evolved a way to fix that problem: forced deep breathe.