The peripheral nervous system consists of which structures?

• A. Cranial nerves and spinal nerves
• B. Brain and spinal cord
• C. Neural crests only
• D. Spinal cord within the vertebrae

Answer: (A)

The peripheral nervous system comprises all nerves outside the brain and spinal cord. The cranial nerves emerge directly from the brain, and the spinal nerves exit the spinal cord; together they connect the central nervous system to the rest of the body, carrying sensory information to the brain and motor commands from the brain to muscles and glands, including autonomic pathways. The brain and spinal cord themselves form the central nervous system, not the peripheral. Embryologic neural crests contribute to many peripheral structures (like dorsal root and autonomic ganglia), but they are sources of components rather than the PNS as a whole. The spinal cord, even when protected inside the vertebrae, remains part of the central nervous system.