Which body system coordinates internal communication and responses to stimuli?

• A. Digestive system
• B. Nervous system
• C. Endocrine system
• D. Circulatory system

Answer: (B)

Rapid, precise internal communication and immediate responses to stimuli are governed by the nervous system. It uses neurons to transmit electrical signals quickly between the brain, spinal cord, and the rest of the body, allowing sensory information to be processed and motor responses to be generated. This fast signaling enables reflexes and coordinated actions. Other systems contribute in different ways—hormones in the endocrine system regulate longer-term processes more slowly, the circulatory system mainly transports blood and substances, and the digestive system handles nutrient processing. So the nervous system is the network that coordinates quick, targeted responses to changes in the environment.