Which structures compose the central nervous system?

• A. Brain and spinal cord
• B. Peripheral nerves
• C. Muscles
• D. Nerves only

Answer: (A)

Brain and spinal cord form the central nervous system. They act as the command center, processing sensory input, coordinating movements, and handling higher functions like thinking and memory. The nerves that run to and from the CNS belong to the peripheral nervous system, serving as communication lines between the brain/spinal cord and the rest of the body. Muscles are the targets of neural signals (they are the effectors) and are not part of the CNS itself. So the brain and spinal cord best fit the structures that make up the central nervous system.