Which structures are included in the nervous system?

The nervous system is a complex network that plays a critical role in controlling and coordinating various functions of the body. It includes the brain, spinal cord, and nerves, which work together to transmit signals throughout the body, enabling communication between different parts of the body and processing information.

The brain serves as the control center, processing sensory information and coordinating responses. The spinal cord acts as a major conduit for signals between the brain and the rest of the body, while the nerves extend from the spinal cord to various regions, facilitating communication between the central nervous system and peripheral systems. This organization is essential for maintaining homeostasis, enabling movement, and processing sensory inputs.

Other structures mentioned in the answer choices do not belong to the nervous system: the heart, lungs, and blood vessels are components of the circulatory system; muscles, tendons, and ligaments are part of the musculoskeletal system; and the stomach, intestines, and pancreas are associated with the digestive system. Thus, the choice of brain, spinal cord, and nerves accurately represents the structures that comprise the nervous system.