Brain. This organ serves as the center of the central nervous system. It exerts control over the other organs in the body. It acts on other orgasn both by controlling muscle activity and secretions of hormones. The response of brain primarily depends on the stimuli from the environment.The interior of the brain whem viewed will show gray matter and white matter. Brain operations is now usderstood however, the way they cooperate is still not fully understood. Function controlled by brain are perception, motor control, arousal, homeostasis, motivation, learning and memory.