Hypothalamus maintains the constant human body temperature by regulation of the diameter of blood vessels (constriction or dilation), shivering and sweating mechanisms. Option B is correct. Cerebrum serves to receive sensory inputs, to bring about integration before commanding voluntary motor responses, to coordinate the activities of other part of brain, and to carry out higher thought processes for learning, memory, language and speech. This makes option A incorrect. Cerebellum serves to coordinate the voluntary movements of skeletal muscles as well as posture, balance and equilibrium. Option C is incorrect. Medulla oblongata consists of reflex centres that control heartbeat, blood vessel diameter and rhythm of breathing as well as other vital functions. Option D is incorrect. Correct answer is B.