Which system uses chemical signals released into the bloodstream to regulate body processes?

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

Answer: (B)

The endocrine system uses chemical signals released into the bloodstream to regulate body processes. Hormones produced by glands travel through the blood to distant target organs, coordinating functions such as metabolism, growth, and reproduction. This type of signaling is slower to start but longer-lasting compared with the rapid, local signaling of the nervous system, which uses electrical impulses and neurotransmitters across synapses. The circulatory system merely transports blood (and the hormones it carries), while the digestive system focuses on breaking down and absorbing nutrients. So, the endocrine system best fits the description.