The document summarizes the human nervous system and its main components. It describes how sense organs receive stimuli from both external and internal environments and send sensory information to the central nervous system via sensory nerves. The central nervous system, which includes the brain and spinal cord, interprets this information and can initiate either involuntary reflex responses via the spinal cord or voluntary motor responses via the brain. It also briefly outlines the main functions and components of several other body systems, including the musculoskeletal, digestive, respiratory, circulatory, excretory, and sensory systems.