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Name Class Date Endocrine and Reproductive Systems Homeostasis Q: How does the body use chemical signals to maintain homeostasis? WHAT I KNOW 34.1 How does the body send and receive chemical signals? 34.2 What life processes are regulated by hormones? 34.3 What body structures enable humans to produce offspring? 34.4 How does a human develop from a single cell to a newborn baby? WHAT I LEARNED SAMPLE ANSWER: The body has hormones that carry chemical signals. Chemical messengers called hormones travel through the blood and bind to receptors on or in target cells. Hormones are produced and released by endocrine glands. SAMPLE ANSWER: Hormones regulate many life processes such as reproduction. SAMPLE ANSWER: Hormones regulate many cycles such as reproductive and sleep cycles. They also help maintain homeostasis through feedback mechanisms that control temperature, blood sugar levels, mineral levels in blood, and water balance. SAMPLE ANSWER: Humans have male and female reproductive organs that produce sperm and eggs. SAMPLE ANSWER: Human reproductive organs, ovaries and testes, are endocrine glands regulated by pituitary hormones. These glands produce hormones that help produce eggs and sperm and secondary sex characteristics. SAMPLE ANSWER: SAMPLE ANSWER: The first cell of a new individual forms from the fertilization of an egg by a sperm. SAMPLE ANSWER: Following fertilization, repeated mitosis and the migration of cells into three cell layers lead to the formation of an embryo. The embryo develops into a fetus that emerges through the vagina during childbirth. Chapter 34 • Workbook A • Copyright © by Pearson Education, Inc., or its affiliates. All Rights Reserved. 529 Name Class Date 34.1 The Endocrine System Lesson Objectives Describe the structure and function of the endocrine system. Explain how hormones work. Lesson Summary Hormones and Glands The endocrine system is made up of endocrine glands that release hormones into the blood. ▶ Hormones are chemicals made in one part of the body that affect cells in other parts of the body. Hormones travel throughout the body in the bloodstream. • Hormones bind to target cells, which are cells that have specific receptors for a hormone either in the cell membrane or inside the cell. • A hormone will not affect a cell that does not have receptors for the hormone. ▶ Glands are organs that release secretions. The body has two types of glands. • Exocrine glands release their secretions through ducts either outside the body or into the digestive system. • Endocrine glands release hormones directly into the bloodstream. Other structures that are not usually considered glands, such as bones, fat tissue, the heart, and the small intestine, also produce and release hormones. ▶ All cells, except for red blood cells, produce hormonelike substances called prostaglandins. Prostaglandins are modified fatty acids that usually affect only nearby cells and tissues. They are sometimes called “local hormones.” Hormone Action There are two types of hormones. ▶ Steroid hormones are produced from cholesterol. They can cross cell membranes of target cells, bind with their receptors, and enter the nucleus. The hormone-receptor complexes change the expression of genes in the target cell, often resulting in dramatic changes in the cell’s activity. ▶ Nonsteroid hormones can be proteins, small peptides, or modified amino acids. They cannot cross cell membranes. The receptors for nonsteroid hormones are on the cell membrane. Compounds called secondary messengers carry the messages of nonsteroid hormones inside target cells. Hormones and Glands For Questions 1–4, write True if the statement is true and False if the statement is false. True 1. Hormones are chemical messengers that are transported by the bloodstream. False 2. Any cell can be a target cell for a hormone. False 3. The body’s response to hormones is the same as it is for nerve impulses. True 4. Insulin and glucagon are two opposing hormones. Lesson 34.1 • Workbook A • Copyright © by Pearson Education, Inc., or its affiliates. All Rights Reserved. 530 Name Class Date 5. Complete the table that summarizes major endocrine glands of the human body. Gland Hormone(s) Produced Function Parathyroid Parathyroid hormone Regulates the level of calcium in the blood Pineal Melatonin Regulates rhythmic activities Thyroid Thyroxine Regulates the body’s metabolism Adrenal Corticosteroids, epinephrine, norepinephrine Helps the body respond to stress Pancreas Insulin, glucagon Maintains the level of glucose in the blood Ovaries Estrogen, progesterone Regulates formation of eggs and development of secondary female sex characteristics; prepares uterus for fertilization Testes Testosterone Regulates production of sperm and secondary male sex characteristics 6. What are prostaglandins? How is their action different from that of hormones? Prostaglandins are modified fatty acids that are produced by nearly every cell and that act like hormones. They act only on nearby cells and tissues, whereas hormones can act on target cells throughout the body. Lesson 34.1 • Workbook A • Copyright © by Pearson Education, Inc., or its affiliates. All Rights Reserved. 531 Name Class Date Hormone Action 7. Steroid and nonsteroid hormones affect their target cells in different ways. In the spaces below, draw diagrams that show how each type of hormone affects its target cells. Be sure to label the cell membrane, cytoplasm, nucleus, the hormones, and their receptors. How Steroid Hormones Work How Nonsteroid Hormones Work See the textbook for what this drawing should look like. Drawings should show the hormone binding with the receptor complex inside the cell and then entering the nucleus of the cell. See the textbook for what this drawing should look like. Drawings should show the hormone binding with the receptor on the cell membrane of the cell. 8. Summarize the action of a steroid hormone on a target cell. A steroid hormone passes through the cell membrane and binds with a receptor inside the cell. The hormone-receptor complex then passes into the nucleus. The complex binds to a region of DNA that controls gene expression. This causes certain genes to be transcribed into mRNA that goes into the cytoplasm and directs protein synthesis. 9. Summarize the action of a nonsteroid hormone on a target cell. A nonsteroid hormone binds to a receptor on the cell membrane. This activates enzymes inside the cell. The enzymes cause the release of secondary messengers, which are molecules that activate or inhibit cell activities. 10. Compare the release of a hormone to the broadcast of a television commercial. SAMPLE ANSWER: A television commercial only affects the behavior of people who are interested in buying the product the commercial advertises (the target audience). A circulating hormone only affects the activities of cells with receptors (target cells) for that hormone. Neither the commercial nor the hormone will affect a “non-target.” Lesson 34.1 • Workbook A • Copyright © by Pearson Education, Inc., or its affiliates. All Rights Reserved. 532 Name Class Date 34.2 Glands of the Endocrine System Lesson Objectives Identify the functions of the major endocrine glands. Explain how endocrine glands are controlled. Lesson Summary The Human Endocrine Glands Endocrine glands are scattered throughout the body. ▶ The pituitary gland is a bean-size structure at the base of the brain. Consisting of two parts, the anterior pituitary and the posterior pituitary, it secretes hormones that regulate body functions and control the actions of other endocrine glands. ▶ The hypothalamus controls the secretions of the pituitary gland and is the link between the central nervous system and the endocrine system. The hypothalamus controls the posterior pituitary through neurosecretory cells. The hypothalamus produces releasing hormones that control the secretions of the anterior pituitary. ▶ An adrenal gland sits on top of each kidney. The adrenal glands make hormones that help the body prepare for and deal with stress. They consist of a cortex and a medulla. • The adrenal cortex produces more than two dozen corticosteroids, which help maintain homeostasis. • The adrenal medulla produces the “fight or flight” hormones epinephrine and norepinephrine, which help the body respond to stress. ▶ The pancreas is both an exocrine gland and an endocrine gland. As an exocrine gland, the pancreas releases digestive enzymes. ▶ Insulin and glucagon, hormones produced by the islets of Langerhans in the pancreas, help keep levels of glucose in the blood stable. ▶ The thyroid gland wraps around the trachea at the base of the neck. The four parathyroid glands are on the back surface of the thyroid gland. Thyroxine, produced by the thyroid gland, regulates metabolism. A hormone from the thyroid gland, calcitonin, and one from the parathyroid glands, parathyroid hormone, work together to maintain blood calcium levels. ▶ Reproductive glands, or gonads, make gametes and secrete sex hormones. The female gonads, ovaries, produce eggs. The male gonads, testes, produce sperm. Control of the Endocrine System Feedback mechanisms involving hormones help maintain homeostasis. In feedback inhibition, increasing levels of a substance inhibit the process that produced the substance. Secretions of the hypothalamus and pituitary gland regulate the activity of other endocrine glands in this way. ▶ Actions of the hypothalamus and posterior pituitary gland regulate water balance. The hypothalamus signals the posterior pituitary gland to increase (in the case of dehydration) or decrease (in the case of overhydration) its release of anti-diurectic hormone (ADH). In response to ADH levels the kidneys produce less or more urine. ▶ The hypothalamus and anterior pituitary regulate metabolism and body temperature by controlling the amount of thyroxine produced by the thyroid gland. Lesson 34.2 • Workbook A • Copyright © by Pearson Education, Inc., or its affiliates. All Rights Reserved. 533 Name Class Date The Human Endocrine Glands For Questions 1–4, complete each statement by writing the correct word or words. brain 1. The pituitary gland is located at the base of the anterior Neurosecretory 2. released by the posterior pituitary and the posterior pituitary pituitary. hypothalamus cells in the and consists of the produce hormones that are . 3. The two hormones released from the posterior pituitary are oxytocin and antidiuretic hormone . 4. Releasing hormones secreted into blood vessels leading to the anterior pituitary control its secretions. For Questions 5–9, match each pituitary hormone with its action. Hormone Action E 5. MSH A. Stimulates ovaries and testes B 6. TSH B. Stimulates the release of thyroxine A 7. LH C. Stimulates release of hormones from adrenal cortex D 8. GH D. Stimulates protein synthesis and growth in cells C 9. ACTH E. Stimulates melanocytes to increase production of melanin in the skin 10. Complete the table. Fill in the missing information about each adrenal gland. Part of the Adrenal Gland Hormone(s) Produced Function Adrenal cortex Corticosteroids Regulating blood volume and pressure, metabolism Adrenal medulla Epinephrine, norepinephrine Producing “fight or flight” response 11. How does the pancreas use insulin and glucagon together to control blood glucose levels in the body? When blood glucose rises after a person eats, the pancreas releases insulin to promote the uptake of glucose from the blood. Once the level drops, the pancreas releases glucagon to stimulate the release of glucose into the blood. 12. What is diabetes mellitus? It is a condition that develops when the pancreas fails to produce insulin or body cells do not properly respond to insulin. Lesson 34.2 • Workbook A • Copyright © by Pearson Education, Inc., or its affiliates. All Rights Reserved. 534 Name Class Date For Questions 13–19, write True if the statement is true. If the statement is false, change the underlined word or words to make the statement true. True iodine hypothyroidism True 13. A major role of the thyroid gland is controlling the body’s metabolism. 14. The body needs calcium in order to produce thyroxine. 15. Too little thyroxine leads to a condition called hyperthyroidism. 16. Calcitonin is a hormone produced by the thyroid gland. thyroid 17. The parathyroid glands are located on the back of the pituitary gland. True 18. Parathyroid hormone promotes the proper functioning of nerves and muscles. gonads 19. The reproductive organs are referred to as gametes. Control of the Endocrine System 20. What is feedback inhibition? Feedback inhibition is a process in which an increase in a product slows or stops the process that produces the product. 21. Complete the flowchart to show how feedback controls regulate the thyroid gland. Inhibition Hypothalamus TRH Anterior pituitary TSH Thyroid Thyroxine 22. Explain how feedback control regulates the rate of metabolism. The hypothalamus produces thyroid-releasing hormone (TRH), which stimulates the anterior pituitary to produce thyroid-stimulating hormone (TSH), which causes the thyroid gland to produce thyroxine, which increases the rate of metabolism. Rising levels of TSH and thyroxine in the blood both cause the hypothalamus to slow or stop production of TRH, which leads to the slowing of the metabolic rate. 23. Which gland, the hypothalamus or the pituitary gland, should be given the title “master gland”? Explain your choice. SAMPLE ANSWER: The hypothalamus should really be called the “master gland.” Even though the pituitary gland’s hormones affect many of the body’s organs and functions, the hypothalamus controls the secretions of the pituitary gland. Lesson 34.2 • Workbook A • Copyright © by Pearson Education, Inc., or its affiliates. All Rights Reserved. 535