Sleep deprivation

What is sleep deprivation?
There's little evidence that lack of sleep, or sleep deprivation as it's known, causes any immediate physiological damage to the body. But it certainly affects how you feel and how your brain works, and it can interfere with work and home life.
If it goes on for a long time, there may be some risk that it can cause some health problems, such as aggravating existing heart disease.

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Symptoms

Few people actually like feeling tired, and that sense of fatigue can make you grumpy, irritable and unable to function properly. Chronic tiredness can increase vulnerability to depression and accentuate other mood problems such as anxiety.
Sleep deprivation can also affect your performance by reducing cognitive ability - your ability to think and use your brain. Combined with drowsiness, this can greatly increase the risk of accidents because you're less able or quick at thinking your way fast out of a dangerous problem.
Along with the delays and errors in doing mental tasks, there's a slowing down of mental arithmetic and logical reasoning. Memory is affected by sleep deprivation, with reduced immediate recall, although information acquired before sleep deprivation is normal.
Although it reduces the ability to do simple or monotonous tasks, the ones that need more attention and effort aren't so badly affected. Attention and concentration can drag a tired brain into action. However, certain aspects of these complex tasks are affected, particularly the ability to think laterally.

Treatment and recovery

No one is sure of the purpose of sleep, but it seems it may be at least partly related to rest and repair of the body's tissues. While many organs in the body can rest and recover during relaxed wakefulness, a part of the brain called the cerebral cortex can only do this during sleep. We have yet to learn what happens if the cortex is deprived of this chance to recover.
Make the most of every opportunity to catch up on sleep, including short cat-naps or occasional lie-ins if possible.
read more : http://www.bbc.co.uk/health/physical_health