The endocrine system, like the nervous system, controls body activities to maintain a relatively constant internal environment. The methods used by these two systems are different. This chapter describes the difference between endocrine and exocrine glands, the location of the endocrine glands, and the hormones they secrete (objectives 1 and 6). It explains the nature of hormones, the substances that function as hormones, how hormones affect target tissues, how the secretion of hormones is controlled by a negative feedback system and the nervous system, the general function of each hormone, and the result of too little or too much of each hormone (objectives 2-5, 7, and 8). In addition, the text distinguishes between physical and psychological stress and describes how the endocrine system mediates the stress response (objectives 9 and 10).

A knowledge of the function of the endocrine system is basic to the understanding of how metabolic processes are regulated to meet the changing needs of the body.