The human brain is the anteriormost part of the central nervous system in humans as well as the primary control center for the peripheral nervous system.
The brain controls "lower" or involuntary activities such as heartbeat, respiration, and digestion - these are known as autonomic functions- as well as sensation, movement, and a variety of special senses. The brain also controls "higher" order, conscious activities, such as thought, reasoning, and abstraction.
The human brain is generally regarded as more capable of these higher order activities than that of any other known species.
(Original: wikipedia.org)