The endocrine system

The endocrine system and the nervous system work closely together to help us respond to our environment. This is a system of organs ( endocrine glands) that releases chemical message molecules, called hormones, into the blood. Unlike the nervous system whose action helps the body react immediately to change, the endocrine system controls changes that happen to the body over a long period of time; from minutes, hours, to years of change. The endocrine system is important in controlling metabolism, growth and development, reproduction, and salt, water and nutrient balance of blood and other tissues
Organs of the Endocrine System
The endocrine system is made up of many glands that are located in different areas of the body. Hormones are made and secreted by cells in endocrine glands. Endocrine glands are ductless organs that secrete hormones directly into the blood or the fluid surrounding a cell rather than through a duct. The major glands of the endocrine system are shown in Figure. Many other organs, such as the stomach, heart, and kidneys secrete hormones and are considered to be part of the endocrine system.

• Hypothalamus
• Pituitary gland
• Thyroid
• Adrenal glands
• Pancreas
• Ovary (female)
• Testicles (male)

You can take a look to a video about endocrine system to learm the vocabulary.
Hormones
The body produces many different hormones, but each hormone is very specific for its target cells. A target cell is the cell on which a hormone has an effect. Target cells are affected by hormones because they have receptor proteins that are specific to the hormone. Hormones will travel through the bloodstream until they find a target cell with the specific receptors to which they can bind. When a hormone binds to a receptor, it causes a change within the cell.
The effects of hormones vary widely, and certain hormones, called tropic hormones (or tropins), regulate the production and release of other hormones. Many of the responses to hormones regulate the metabolic activity of an organ or tissue.