Though sleepy is a signal the body needs sleep, as well as hunger is a sign of needed food or a thirst which means require liquid. Sleepiness is a natural thing. Naturally, if the lack of something we have to meet those needs, and not replaceable. Yes, until now, no one else can replace substance restorative effects of sleep.
The sleep process to build and repair the body. He gives new energy, new spirit even new cells. All body systems will be disrupted so disturbed sleep.
Basically we will be sleepy if the lack of sleep. But lack of sleep should be understood as a condition. Lack of sleep can be caused by lack of sleep duration, or poor quality sleep. Poor sleep quality, not just sleep that is not in the sense that the public is often known as napping. Poor sleep quality found in the form of excessive sleepiness even though the duration of sleep is enough.
