Which part of the brain is primarily responsible for voluntary movement and complex thought processes?

The cerebrum is primarily responsible for voluntary movements and complex thought processes. It is the largest part of the human brain and plays a crucial role in various higher-order functions, including reasoning, problem-solving, and planning. The cerebrum is divided into two hemispheres, each responsible for different cognitive and motor functions, and contains regions known as lobes, which further specialize in handling specific tasks such as language, sensory perception, and spatial awareness.

In contrast, the cerebellum, located at the back of the brain, is mainly involved in coordination and balance rather than voluntary movements or complex thought processes. The medulla oblongata is part of the brainstem and controls autonomic functions such as breathing and heart rate, which are not related to voluntary movements or complex thought. The pons, also a part of the brainstem, mainly serves as a conduit for signals between the cerebellum and the cerebrum and is involved in regulating sleep and arousal, rather than complex cognitive tasks or voluntary motor functions. Thus, the cerebrum is distinctively suited to manage the responsibilities mentioned in the question.