The human brain is the command center of the nervous system located in the skull. It receives sensory input and controls muscle output. The brain is divided into three main sections - the cerebrum, brainstem, and cerebellum. The cerebrum is the largest part and is divided into four lobes which control different functions like vision, sound, language, and spatial reasoning. The brainstem connects the brain to the spinal cord and controls vital functions. Between the cerebrum and brainstem are the thalamus and hypothalamus which relay signals and regulate bodily processes.