In the central nervous system, activities of numerous neurons are integrated to constitute a number of major functional blocks, each characterized by unique structural and functional features. Five controller systems are centers of reflexes, compound movements and innate behaviors in the brainstem and spinal cord and those of the sensory/motor and executive/cognitive functions in the cerebral neocortex. Four regulator systems are the sleep-wakefulness centers in the brainstem, cerebellum, basal ganglia and limbic system. This article describes characteristic features of these nine systems based on current knowledge of neuroscience, and attempts to account for several important aspects of the central nervous system (hierarchy, top-down operation, internal model and will) by compounding these component functions.