The Endocrine System

Life Science - Middle School

endocrine cell hormones target body cell hormone receptor hormone receptor complex blood vessel adrenal gland kidney The Endocrine System © C opyright NewPath Learning. All Rights Reserved. 94-4909 The endocrine system controls many of the body’s daily activities and regulates growth and development. It is made up of glands known as endocrine glands which are organs that produce and secrete special chemicals called hormones into the bloodstream. Hormones Hormones control many different functions of the body by speeding up, slowing down, or turning on or off the activities of various organs. Because hormones are transported by the blood, they are able to regulate body activities far away from the glands that they are produced in. Hormones are able to target a specifi c organ because they all have a unique chemical structure. A particular hormone will only react with specifi c target cells. A target cell is a cell that will only recognize a hormone that has a certain chemical structure. Glands of the Endocrine System The endocrine system is controlled by the nervous system. When a hormone is released from an endocrine gland, the brain sends a nerve impulse to the gland telling it to release the hormone. Negative Feedback The endocrine system maintains homeostasis the same way that your house is heated during the winter months. Once the heat drops down to a certain point, the heat will turn on and warm the house to the set temperature and then turns off. This system is called negative feedback. Cold Hypothalamus Anterior Pituitary Thyroid Hormone released (thyroxine) + + + + Temperature increases The hypothalamus is a small part of the brain which links the nervous system and the endocrine system and controls the pituitary gland. The pituitary gland releases hormones in response to receiving nerve impulses from the hypothalamus. The hormones from the pituitary gland turn other endocrine glands on. The thyroid gland controls the metabolism of food. The parathyroid glands control the level of calcium found in blood. The pancreas regulates the level of sugar (glucose) in blood by producing the hormones insulin and glucagon. The adrenal glands release adrenaline in response to an emergency situation and help to maintain salt and water balance in the kidneys and sugar in the blood. The testes release the sex hormone testosterone which controls male development. The ovaries release the sex hormone estrogen which controls female development. The thymus produces hormones that stimulate the production of some infection-fi ghting cells and in maturing T cells, an important part of our immune system.
endocrine cell insulin estrogen metabolism glucagon negative feedback homeostasis nerve impulse hormone estrogen target cell hormone receptor testosterone hormone receptor Key Vocabulary Terms complex \xiBAHBDy01780mzV The Endocrine System © C opyright NewPath Learning. All Rights Reserved. 94-4909 Hormones What are hormones ? __________________________________________ ____________________________________________________________ What do hormones control? ____________________________________ ____________________________________________________________ ____________________________________________________________ Glands of the Endocrine System Describe the glands of the endocrine system: The hypothalamus _____________ _____________________________ _____________________________. The pituitary gland ______________________ _____________________ ____________________ ____________________ . The thyroid gland ____________ __________________________ ________________________ ______________________. The parathyroid glands ________________________ ________________________. The pancreas ________________ ____________________________ ____________________________ ____________________________ ____________________________. The adrenal glands _________ __________________________ __________________________ __________________________ __________________________. The testes _________________ _____________________________ ________________________________. The ovaries _________________________ _________________________ _________________________. The thymus ___________ ____________________ ____________________ ____________________ ____________________. What is the role of the endocrine system ? ______________________________ __________________________________________________________________