The human body, like all other animals, requires rest so as to function properly. The human body requires sleep so as to carry out a number of bodily functions at rest. While sleeping, the heart rate slows down which allows the heart to rejuvenate itself so as to pump blood again throughout the next day.
Since the heart is an involuntary muscle, it keeps on working throughout the day and needs some rest. Same is the case with the human brain. There is a capacity to which one can absorb information beyond which the mind needs some rest so as to rejuvenate itself.
