Section 18.1 The Endocrine System Objectives Describe the general roles of the endocrine system. Identify the glands of the endocrine system.
Health Stats What trends in growth rate does this graph show? Does your observation of classmates support the trends shown in the graph? Explain.
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 (EN duh krin) 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 GlandThe thyroid gland regulates the body’s overall metabolic rate and controls calcium levels in the bloodstream. Parathyroid GlandsFour 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. PancreasThe pancreas is a large gland, located behind the stomach, that controls sugar levels in the blood.
HypothalamusThe hypothalamus links the nervous system and the endocrine system and controls many of the pituitary gland functions. The Endocrine System Pituitary GlandThe pituitary gland controls other endocrine glands and regulates growth rate, reproduction, and metabolism. Thymus GlandHormones released by the thymus gland help the immune system develop during childhood. By adolescence, this gland has shrunkconsiderably in size. Adrenal GlandsThese 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 OvariesThe female reproductive glands release sex hormones that regulate egg maturation and control changes in a female’s body at puberty. TestesThe male reproductive glands release a sex hormone that regulates sperm production and control changes in a male’s body at puberty.
Hypothalamus • The hypothalamus (hy poh THAL uh mus), 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 (pih TOO ih tehr ee). • 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.
Vocabulary 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.
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End of Section 18.1 Click on this slide to end this presentation.