Which system is primarily involved when stress causes headaches and body aches?

The correct answer is the musculoskeletal system. When stress is experienced, it can lead to muscle tension and tightness, which are common physical responses. This muscle tension can manifest in the form of headaches and body aches. The musculoskeletal system comprises muscles, bones, tendons, and ligaments, and its response to stress often includes contractions and stiffness, contributing directly to the discomfort experienced.

While the nervous system also plays a crucial role in how stress is perceived and processed in the body, the specific symptoms of headaches and body aches are more closely tied to the musculoskeletal components reacting to that stress. As such, while other systems are involved in the overall experience of stress, the primary system responsible for these particular physical symptoms is the musculoskeletal system.