Which of the following structures comprise the central nervous system?

• A. Heart and lungs
• B. Brain and spinal cord
• C. Nerves
• D. Muscles

Answer: (B)

The central nervous system is made up of the brain and spinal cord, which together act as the body’s main control center and the pathway for messages between the brain and the rest of the body. The brain processes information, makes decisions, and coordinates actions, while the spinal cord transmits signals to and from the brain and handles simple reflexes. The heart and lungs belong to the cardiopulmonary system and are not part of the CNS. Nerves belong to the peripheral nervous system, carrying signals between the CNS and muscles or organs. Muscles are the effectors that respond to nervous system signals, not part of the CNS itself. Therefore, brain and spinal cord are the structures that comprise the central nervous system.