What are the messenger molecules of the endocrine system?
acids
neurons
enzymes
hormones
Hormones are the messenger molecules of the endocrine system. Endocrine hormones travel throughout the body in the blood. However, each hormone affects only certain cells, called target cells. A target cell is the type of cell on which a hormone has an effect. A target cell is affected by a particular hormone because it has receptor proteins that are specific to that hormone. A hormone travels through the bloodstream until it finds a target cell with a matching receptor it can bind to. When the hormone binds to a receptor, it causes a change within the cell. Exactly how this works depends on whether the hormone is a steroid hormone or a non-steroid hormone . At the link below, you can watch an animation that shows how both types of hormones work. http://www. wisc-online. com/objects/ViewObject. aspx?ID=AP13704.