Which structures make up the human nervous system?

The human nervous system consists of the brain, spinal cord, and nerves, which together facilitate communication throughout the body and coordinate responses to internal and external stimuli.

The brain serves as the central control center, processing sensory information and coordinating actions. The spinal cord acts as a major conduit for information traveling between the brain and the rest of the body, playing a crucial role in reflexes. Nerves extend from the spinal cord to various parts of the body, transmitting signals that regulate bodily functions, movements, and sensory perceptions.

Other options do not pertain to the nervous system. The heart, lungs, and blood are components of the circulatory system, responsible for blood circulation and oxygen delivery. Muscles and bones make up the muscular and skeletal systems, providing structure and enabling movement. Skin, hair, and nails are components of the integumentary system that protects the body and regulates temperature. Therefore, the correct answer reflects the specific structures that constitute the nervous system.