Which system sends messages from the brain to each part of the body?

The central nervous system (CNS) is the primary system responsible for processing information and sending messages from the brain to other parts of the body. It includes the brain and spinal cord, which work together to interpret sensory information and coordinate motor responses. The brain generates commands that travel through the spinal cord and peripheral nerves, reaching various body parts to enact movements or responses.

Understanding the roles of the other systems is important as well. The peripheral nervous system (PNS) connects the CNS to limbs and organs, functioning more as a communication highway rather than the control center itself. The autonomic nervous system, a subset of the PNS, manages involuntary bodily functions such as heart rate and digestion. The term "circular nervous system" is not a recognized part of human anatomy, which makes it an incorrect choice in this context.