Chemical messengers, mostly those manufactured by the endocrine glands, that are produced in one tissue and affect another are called what?

• A. Neurotransmitters
• B. Endocrine System
• C. Hormones
• D. Receptors

Answer: (C)

Hormones are chemical messengers produced by endocrine glands that travel through the bloodstream to distant tissues and organs, where they regulate functions such as metabolism, growth, and reproduction. This long-distance signaling distinguishes them from other signals in the body. For example, neurotransmitters are also chemical messengers, but they are released by neurons and typically act across synapses on nearby cells, not through the bloodstream to distant targets. The endocrine system refers to the network of glands that produce these messengers, not the messengers themselves. Receptors are the proteins on target cells that bind hormones and initiate a response, so they’re the receiving sites, not the sending messengers.