Ideal sleep duration varies. Newborns sleep 16-20 hours a day. This number continued to decline in children under 10 years to 10-12 hours per day, over 10 years of 9-10 hours per day, and in adulthood from 6.5 to 7.5 hours per day. Less or more than it can be bad.
Kripke studies cited in Time magazine and CNN (2010) explains, people with hours of sleep ideal-especially at night-most long-lived. Conversely, people who slept eight hours or more and sleep less than 6.5 hours shorter-lived. Deficiency or excess of sleep also have an impact on depression, obesity, and heart disease.
Actually, experts do not know exactly why sleep is so meaningful. However, as revealed in the WebMD site, they suspect it is related to part of the brain called the hippocampus and neocortex that function to save memory. During sleep, the hippocampus will replay all the events that day to the neocortex and then save it for the long term.
Some experiments show, there are certain memories that become stable in the period of sleep called rapid eye movement (REM) or rapid eye movement, which is when we dream. Several other types of memory stored in the period just started, known as slow wave sleep soundly. In addition, all creatures are undergoing life cycle according to the rhythm of rotation of the Earth, 24 hours a day, called circadian rhythms. In humans, circadian-control center located in the brain called the ventral anterior hypothalamus-resting the body and stimulates the cells at night. That’s why sleep is important for survival.