Which system controls nearly all activities in the body, both voluntary and involuntary?

The nervous system is responsible for controlling nearly all activities in the body, both voluntary and involuntary. It comprises the brain, spinal cord, and peripheral nerves, allowing for communication between different body parts and the central processing unit (the brain).

Voluntary activities, such as movement and speaking, are managed by the somatic nervous system, a branch of the peripheral nervous system that controls skeletal muscles. Involuntary activities, including heart rate, digestion, and respiratory functions, are regulated by the autonomic nervous system, which operates without conscious control.

This comprehensive control over various physiological functions is essential for maintaining homeostasis, responding to environmental changes, and facilitating complex behaviors. The other systems listed—musculoskeletal, respiratory, and digestive—play specific roles but do not exert the same level of overarching control over the body's functions as the nervous system does.