The endocrine system plays an important role in homeostasis because hormones regulate the activity of body cells. The release of hormones into the blood is controlled by a stimulus. For example, the stimulus either causes an increase or a decrease in the amount of hormone secreted.When homeostasis is not maintained, the body cannot function properly and illness may ensure. Homeostasis is the process in which the body's overall internal environment is kept constant in response to any external environmental changes. This involves maintaining stability in different body systems.