Which system is outside the central nervous system?

• A. Endocrine system
• B. Central nervous system
• C. Digestive system
• D. Peripheral nervous system

Answer: (D)

The key idea is identifying which part lies outside the brain and spinal cord. The central nervous system is composed of the brain and spinal cord. The network that routes signals to and from the rest of the body—outside of the brain and spinal cord—is the peripheral nervous system. It includes all the nerves branching out to sensory receptors, muscles, and organs, so it sits outside the CNS. The endocrine and digestive systems are separate body systems; they aren’t part of the nervous system itself, even though they interact with it. So the peripheral nervous system is the system that is outside the central nervous system.