What are hormones?

Hormones are chemical messengers produced and secreted by endocrine glands directly into the bloodstream. Once in the bloodstream, they travel to various organs and tissues throughout the body to regulate numerous physiological processes, including metabolism, growth and development, mood, and sexual function. This systemic influence is a key characteristic of hormones that distinguishes them from other biological substances.

In contrast, nerve impulses, which involve the rapid transmission of signals through neurons, are a different form of communication within the nervous system, focused on immediate reaction and coordination rather than broader regulatory functions. Proteins produced by muscle tissues are mainly involved in muscle contraction and movement, not in hormone production. Enzymes, while important for promoting chemical reactions and aiding in digestion, are not classified as hormones since they serve a different function within the body. The role of hormones in maintaining homeostasis and facilitating communication between various bodily systems is what makes the first choice the correct answer.