Describe the key features of the endocrine system. These signals are protein molecules, steroids or amino-acid derivatives. Hormones are released into the bloodstream and are carried to target tissues.
Hormones interact with receptors on or in target tissues to produce a response.
Describe how the chemical structures of hormones determine the way they interact with their target tissues. They interact with intracellular receptors that may be in the cytoplasm or nucleus. Describe, in general terms, the ways in which the interaction of a hormone with target cells is translated into a response. The interaction of a hormone with a plasma membrane receptor produces a change in the intracellular concentration of one or more signal molecules known as second messengers. The activity of these proteins determines the response of the target tissue.