5. The brain coordinates and directs various body functions. Each
component of the brain controls some aspect of an individual's behavior
and affects the understanding of the world around him or her. The brain
not only controls involuntary movements of organs like heart, kidney but
also initiate voluntary movements like walking, running and also higher
order functions like thinking, reasoning, memory, etc. The abnormal
development functioning of any part of brain thus makes an individual
less able to adjust to the environment and give rise to various disorders,
one of which is mental retardation.