Which of the following is NOT a component of the central nervous system?

The central nervous system (CNS) comprises the brain and spinal cord, which are integral to processing and transmitting information throughout the body. The brain is responsible for higher functions such as thought, emotion, and coordination of movements. The spinal cord serves as the main pathway for transmitting signals between the brain and the rest of the body, facilitating reflexes and involuntary responses.

The optic nerve, however, does not belong to the central nervous system; it is classified as part of the peripheral nervous system (PNS). The optic nerve conveys visual information from the retina in the eye to the brain for processing, but it does not reside within the brain or spinal cord.

The brain stem, on the other hand, is indeed a component of the CNS as it connects the brain to the spinal cord and controls vital functions such as breathing and heart rate. Therefore, identifying the optic nerve as the answer highlights its distinction from the essential components of the central nervous system.