What are hormones primarily responsible for?

Hormones are primarily responsible for regulating the activity of target cells within various organs and tissues of the body. They serve as chemical messengers that are secreted by glands into the bloodstream. Once in circulation, hormones bind to specific receptors on or in their target cells, initiating a response that can influence growth, metabolism, immune responses, and numerous other physiological functions. This regulatory role highlights the importance of hormones in maintaining homeostasis and modulating various biological processes.

The other options do not accurately reflect the primary function of hormones. For instance, while stimulating the production of red blood cells is a specific action of the hormone erythropoietin, this is just one example of what hormones can influence, not their primary role. Conducting electrical signals in the brain pertains to the function of neurons and is not related to hormonal action. Transmitting sensory information is a task primarily managed by sensory neurons and related pathways, distinct from the regulatory functions of hormones.