Functions of Endocrine glands:
Endocrine glands play an important role in maintaining the constancy of internal environment (milieu interior) and hormones integrate and regulate various physiological functions. They regulate the general metabolism viz., the metabolism of carbohydrates, proteins, fats, minerals and water. The endocrine glands also control the reproductive functions of animals. The adrenal hormones prepare the body to meet emergency and stressful situations. The hormones are also responsible for intercellular communication.
Each endocrine gland may secrete excess quantities of its own hormone. However, once the normal physiological response is over, this information is fed back to the endocrine gland. As a result, its secretion decreases or inhibited. Conversely, if the secretion of the hormone is subnormal and the physiological effects or responses are reduced, the information is taken to the gland and it secretes the hormone at an increased rate. Thus, homeostatic equilibrium is restored.
The two major systems of the human body that coordinate, regulate and integrate almost all physiological functions are the nervous system and the endocrine system. The information transmitted by the nervous system in the form of electric impulses is conducted rapidly in the neurons. The signals from the endocrine glands or ductless glands are communicated by means of chemical substances called hormones. The hormones are secreted into and carried by the blood stream from their point of origin to the target organs or tissues. In the target tissues, the hormone action is manifested.
A hormone may be defined as a chemical substance synthesized by the cells of endocrine glands and carried by blood to the site of action where it exerts its physiological effects. Hormones are considered as chemical messengers.