The endocrine system is one of the control systems of the body. Endocrine glands release chemicals called hormones into the bloodstream. These hormones travel to their target organs and cells. They then bind to receptors either on cell surfaces or inside the cell. This results in a change in the activity of those cells.
These responses are relatively slow, taking from seconds to days to occur. In comparison, the nervous system, which uses electrical signalling directly to muscles and other tissues produces responses within milliseconds. However, once initiated, endocrine effects tend to be more prolonged.