Which system sends and receives messages?

• A. Nervous System
• B. Integumentary System
• C. Skeletal System
• D. Circulatory System

Answer: (A)

Messages in the body are carried by the nervous system, which is the body's main communication network. It sends and receives rapid signals through neurons, using electrical impulses and neurotransmitters at synapses to pass information to the brain, muscles, and glands. This system integrates sensory input, processes it, and triggers appropriate actions quickly, like pulling a hand back from a hot surface or adjusting balance. The other systems don’t serve this centralized signaling role: the integumentary system mainly protects the body and houses some skin sensations, the skeletal system provides structure and support, and the circulatory system transports blood, nutrients, and even hormones but does not constitute the rapid messaging network by itself.