The central nervous system comprises which structures?

• A. The central nervous system comprises the brain and spinal cord
• B. The peripheral nervous system comprises the brain and spinal cord
• C. The central nervous system includes cranial nerves
• D. The peripheral nervous system controls breathing

Answer: (A)

The central nervous system is the brain and spinal cord. These structures act as the main processing and command centers: the brain interprets information, makes decisions, and directs actions, while the spinal cord transmits signals between the brain and the rest of the body and can coordinate simple reflexes on its own. Cranial nerves, even though they originate from the brain, are part of the peripheral nervous system because they extend outside the CNS to innervate the head, neck, and beyond. Breathing is controlled by centers in the brainstem (CNS) that send signals via peripheral nerves to the respiratory muscles, so it isn’t accurate to say the peripheral system alone controls breathing.