What is the system called that produces hormones that travel through the bloodstream to target organs?

The system responsible for producing hormones that travel through the bloodstream to target organs is known as the endocrine system. This system consists of various glands that secrete hormones directly into the bloodstream, which then transport these chemical messengers to different parts of the body where they exert their effects on target organs.

Hormones play vital roles in regulating numerous physiological processes, including metabolism, growth and development, tissue function, and mood. The endocrine system operates on a slower time scale compared to the nervous system, which communicates through electrical signals and allows for rapid responses to stimuli.

In this context, the nervous system primarily focuses on immediate reactions and communication between nerve cells, while the circulatory system is responsible for the transport of blood and nutrients throughout the body, not specifically for hormone production. The immune system is concerned with defending the body against pathogens and does not play a direct role in hormone secretion. Thus, the endocrine system is the correct choice for the production and transport of hormones.