Which system of the body directly influences muscle movements?

The nervous system is crucial for influencing muscle movements because it is responsible for sending and receiving signals that control muscle contraction and coordination. Neurons transmit these signals from the brain and spinal cord to the muscles, allowing for precise movement and response to stimuli. This system ensures that voluntary movements, such as walking or typing, are executed smoothly and accurately, as well as involuntary movements like reflexes.

Conversely, while the immune system plays a key role in protecting the body from diseases, it does not directly control muscle movements. The circulatory system is essential for delivering oxygen and nutrients to muscles but does not influence the mechanics of movement itself. The respiratory system is important for gas exchange, providing oxygen for muscle use, but it also does not play a role in the direct control of muscle function. Thus, the nervous system is the one that directly interfaces with and governs muscle activity.