Health Stats What trends in growth rate does this graph show? Does your observation of classmates support the trends shown in the graph? Explain.

Section 18.1 The Endocrine System Goals/ Objectives Describe the general roles of the endocrine system. Identify the glands of the endocrine system.

Key Terms endocrine gland A gland that produces and releases chemical substances that signal changes in other parts of the body. hormone A chemical substance produced by an endocrine gland. hypothalamus An endocrine gland in the brain that is part of both the nervous and endocrine systems. pituitary gland An endocrine gland in the brain that controls many of the body’s functions, including growth, reproduction, and metabolism. puberty The period of sexual development during which a person becomes sexually mature and physically able to reproduce.

Key Terms Endocrine System The body system that consists of glands that produce hormones.

What Is the Endocrine System? The endocrine system regulates long-term changes in the body such as growth and development. It also controls many of your body’s daily activities.

Endocrine Glands Your endocrine system is made up of a group of organs, called endocrine glands. An endocrine gland produces and releases chemical substances that signal changes in other parts of the body. Endocrine glands release substances directly into the bloodstream.

Hormones A chemical substance produced by an endocrine gland is known as a hormone. You can think of a hormone as a chemical messenger. The endocrine system is kept in balance by the coordinated action of various hormones.

Functions of the Endocrine Glands The endocrine glands include the hypothalamus pituitary gland thyroid and parathyroid glands thymus gland adrenal glands pancreas reproductive glands

The Endocrine System Thyroid Gland The thyroid gland regulates the body’s overall metabolic rate and controls calcium levels in the bloodstream. Parathyroid Glands Four tiny parathyroid glands regulate levels of calcium and phosphorus––minerals that are necessary for proper bone and tooth formation and for muscle and nerve activity. Pancreas The pancreas is a large gland, located behind the stomach, that controls sugar levels in the blood.

Hypothalamus The hypothalamus links the nervous system and the endocrine system and controls many of the pituitary gland functions. The Endocrine System Pituitary Gland The pituitary gland controls other endocrine glands and regulates growth rate, reproduction, and metabolism. Thymus Gland Hormones released by the thymus gland help the immune system develop during childhood. By adolescence, this gland has shrunk considerably in size. Adrenal Glands These glands release several hormones. Adrenaline triggers the body’s response to sudden stress. Other hormones affect salt and water balance in the kidneys and general metabolism.

The Endocrine System Ovaries The female reproductive glands release sex hormones that regulate egg maturation and control changes in a female’s body at puberty. Testes The male reproductive glands release a sex hormone that regulates sperm production and control changes in a male’s body at puberty.

Hypothalamus The hypothalamus, an endocrine gland located in the brain, is actually part of both the nervous and the endocrine systems. Nerve signals from the hypothalamus control body temperature and feelings of sleep and hunger. Hormones from the hypothalamus control the body’s water levels.

Pituitary Gland “Releasing hormones” from the hypothalamus signal the release of hormones from a pea-sized endocrine gland in the brain, called the pituitary gland. The pituitary controls many of your body’s functions. These functions include growth reproduction metabolism

Other Endocrine Glands The reproductive glands are an important part of the endocrine system. Puberty is the period of sexual development during which a person becomes sexually mature and physically able to reproduce.

Questions What roles does the endocrine system play in the body? What is a hormone? Explain how hormones reach the cells where they have their effect. List the glands of the endocrine system. What is the hypothalamus? How does it interact with the pituitary gland? How is the onset of puberty related to the endocrine system? A driver brakes suddenly when a dog darts out in front of her car. How did the endocrine system aid her quick response?