Which organ is part of the central nervous system?

The brain is an essential part of the central nervous system (CNS), which also includes the spinal cord. The brain is responsible for processing sensory information, controlling motor functions, regulating bodily functions, and facilitating cognitive abilities such as reasoning and emotion. It serves as the central hub for interpreting signals from the body and coordinating responses.

In the context of the other options, the heart, lungs, and stomach are not components of the central nervous system; instead, they are organs in different systems of the body. The heart is part of the circulatory system, responsible for pumping blood; the lungs are part of the respiratory system, involved in gas exchange; and the stomach is part of the digestive system, responsible for breaking down food.