it's kinda hard to explain without a picture but the central nervous system includes the brain and the spinal cord and then the peripheral nervous system includes everything outside the central nervous system. Underneath the peripheral nervous system is the somatic and autonomic nervous systems. The somatic nervous system conveys info from sensory organs to the central nervoys system and motor messages to the body. The autonomic nervous system controls all automatic operations such as breathing. Underneath the autonomic nervous system is the sympathetic nervous system and the parasympathetic nervous system. The sympathetic nervous system prepares the body for arousal when the fight-flight response is activated. The parasympathetic nervous system calms the body after arousal and the threat is removed.