ABSTRACT
The body, if it is to achieve optimal performance, must possess mechanisms for sensing and responding appropriately to numerous biologic cues and signals in order to control and maintain its internal environment. This complex role is effected by the integrative action of the endocrine and neural systems. The endocrine contribution is achieved through a highly sophisticated set of communication and control systems involving signal generation, propagation, recognition, transduction, and response. The signal entities are chemical messengers or hormones that are distributed through the body mainly by the blood circulatory system to their respective target sites, organs, or cells, to modify their activity in some fashion.
