Organ systems in our body cannot functions independently. They have to work hand-in-hand (in coordination with) with other organ systems. For coordinating other systems, our body has two organ systems – the nervous system and endocrine system. You have already learnt about the nervous system. The endocrine system consists of endocrine glands (also called ductless glands) e.g. thyroid gland, pituitary gland. These glands secrete special chemical substances called hormones into the blood. Hormones control and coordinate the various functions of the body, e.g., insulin.