What is the primary function of the nervous system?

The primary function of the nervous system is to detect environmental changes and respond accordingly. This system serves as the body's communication network, facilitating the coordination of various bodily functions. It is responsible for receiving signals from both internal and external stimuli, processing that information, and then transmitting responses to appropriate effectors, such as muscles or glands. This complex processing allows organisms to react to their surroundings, maintain homeostasis, and engage in complex behaviors.

For example, when someone touches a hot surface, sensory receptors in the skin detect the temperature change and send signals to the brain, which quickly processes this information and communicates a response to retract the hand. This rapid communication is crucial for survival and proper functioning.

The other options, while they represent important bodily functions, do not encapsulate the primary role of the nervous system. Promoting muscle movement is one of the effects of nervous system activity, but it does not encompass its full range of functions. Producing hormones is primarily the role of the endocrine system, and filtering toxins from the blood is the function of the renal system. The nervous system's overarching function is its ability to detect changes and facilitate responses.