Chapter 40: Hormones and Endocrine Systems

Transcription

1 Chapter 40: Hormones and Endocrine Systems AP Curriculum Alignment The endocrine system signals to other systems to regulate conditions within our body. There are many adrenal glands and hormones and the Curriculum Framework has an exclusion statement that states that Memorization of the names, molecular structures and specific effects of hormones or features of the brain responsible for these physiological phenomena is beyond the scope of the course and the AP Exam. Big Idea 2 does however contain several illustrative examples that are aimed at the endocrine system such as lactation in mammals and dehydration response to decrease antidiuretic hormone, and Graves disease. All of the illustrative examples are explained in Chapter 40. The endocrine system is one of the human systems that is targeted by the Curriculum Framework. Big Idea 3 specifically calls for the understanding that endocrine signals are produced by endocrine cells that release signaling molecules, which are specific and can travel long distances through the blood to reach all parts of the body. ALIGNMENT OF CONTENT TO THE CURRICULUM FRAMEWORK Big Idea 2: Biological systems utilize free energy and molecular building blocks to grow, to reproduce, and to maintain dynamic homeostasis. Enduring understanding (EU) 2.C: Organisms use feedback mechanisms to regulate growth and reproduction, and to maintain dynamic homeostasis. Essential knowledge (EK) 2.C.1: Organisms use feedback mechanisms to maintain their internal environments and respond to external environmental changes. a. Negative feedback mechanisms maintain dynamic homeostasis for a particular condition (variable) by regulating physiological processes, returning the changing condition back to its target set point. To foster student understanding of this concept, instructors can choose an illustrative example such as: Operons in gene regulation Temperature regulation in animals Plant responses to water limitations b. Positive feedback mechanisms amplify responses and processes in biological organisms. The variable initiating the response is moved farther away from the initial set-point. Amplification occurs when the stimulus is further activated which, in turn, initiates an additional response that produces system change. Students should be able to demonstrate understanding of the above concept by using an illustrative example such as: Lactation in mammals Onset of labor in childbirth Ripening of fruit 554 Mader, Biology, 12 th Edition, Chapter 40

2 c. Alteration in the mechanisms of feedback often results in deleterious consequences. To foster student understanding of this concept, instructors can choose an illustrative example such as: Diabetes mellitus in response to decreased insulin Dehydration in response to decreased antidiuretic hormone (ADH) Graves disease (hyperthyroidism) Blood clotting Big Idea 3: Living systems store, retrieve, transmit, and respond to information essential to life processes. Enduring understanding (EU) 3.D: Cells communicate by generating, transmitting and receiving chemical signals. Essential knowledge (EK) 3.D.1: Cell communication processes share common features that reflect a shared evolutionary history. a. Communication involves transduction of stimulatory or inhibitory signals from other cells, organisms or the environment. b. Correct and appropriate signal transduction processes are generally under strong selective pressure. c. In single-celled organisms, signal transduction pathways influence how the cell responds to its environment. To foster student understanding of this concept, instructors can choose an illustrative example such as: Use of chemical messengers by microbes to communicate with other nearby cells and to regulate specific pathways in response to population density (quorum sensing) Use of pheromones to trigger reproduction and developmental pathways Response to external signals by bacteria that influences cell movement d. In multicellular organisms, signal transduction pathways coordinate the activities within individual cells that support the function of the organism as a whole. To foster student understanding of this concept, instructors can choose an illustrative example such as: Epinephrine stimulation of glycogen breakdown in mammals Temperature determination of sex in some vertebrate organisms DNA repair mechanisms Essential knowledge (EK) 3.D.2: Cells communicate with each other through direct contact with other cells or from a distance via chemical signaling. b. Cells communicate over short distances by using local regulators that target cells in the vicinity of the emitting cell. To foster student understanding of this concept, instructors can choose an illustrative example such as: Neurotransmitters Plant immune response Quorum sensing in bacteria Mader, Biology, 12 th Edition, Chapter

3 Morphogens in embryonic development c. Signals released by one cell type can travel long distances to target cells of another cell type. Evidence of student learning is a demonstrated understanding of the following: 1. Endocrine signals are produced by endocrine cells that release signaling molecules, which are specific and can travel long distances through the blood to reach all parts of the body. To foster student understanding of this concept, instructors can choose an illustrative example such as: Insulin Human growth hormone Thyroid hormones Testosterone Estrogen No specific system, with the exception of the endocrine system, is required for teaching the concepts in 3.D.2. Teachers are free to choose a system that best fosters student understanding. Study of the nervous and immune systems is required for concepts detailed in 3.E.2 and 2.D.4. Essential knowledge 3.D.4: Changes in signal transduction pathways can alter cellular response. a. Conditions where signal transduction is blocked or defective can be deleterious, preventative or prophylactic. To foster student understanding of this concept, instructors can choose an illustrative example such as: Diabetes, heart disease, neurological disease, autoimmune disease, cancer, cholera Effects of neurotoxins, poisons, pesticides Drugs (Hypertensives, Anesthetics, Antihistamines and Birth Control Drugs) Specific mechanisms of these diseases and action of drugs are beyond the scope of the course and the AP Exam. Essential knowledge (EK) 2.C.2: Organisms respond to changes in their external environments. a. Organisms respond to changes in their environment through behavioral and physiological mechanisms. To foster student understanding of this concept, instructors can choose an illustrative example such as: Photoperiodism and phototropism in plants Hibernation and migration in animals Taxis and kinesis in animals Chemotaxis in bacteria, sexual reproduction in fungi Nocturnal and diurnal activity: circadian rhythms Shivering and sweating in humans No specific behavioral or physiological mechanism is required for 556 Mader, Biology, 12 th Edition, Chapter 40

4 teaching the above concept. Teachers are free to choose the mechanism that best fosters student understanding. Enduring understanding (EU) 2.E: Many biological processes involved in growth, reproduction and dynamic homeostasis include temporal regulation and coordination. Essential knowledge 2.E.2: Timing and coordination of physiological events are regulated by multiple mechanisms. b. In animals, internal and external signals regulate a variety of physiological responses that synchronize with environmental cycles and cues. To foster student understanding of this concept, instructors can choose an illustrative example such as: Circadian rhythms, or the physiological cycle of about 24 hours that is present in all eukaryotes and persists even in the absence of external cues Diurnal/nocturnal and sleep/awake cycles Jet lag in humans Seasonal responses, such as hibernation, estivation and migration Release and reaction to pheromones Visual displays in the reproductive cycle Memorization of the names, molecular structures and specific effects of hormones or features of the brain responsible for these physiological phenomena is beyond the scope of the course and the AP Exam. Concepts covered in Chapter 40 also align to the learning objectives that provide a foundation for the course, an inquiry-based laboratory experience, class activities, and AP exam questions. Each learning objective (LO) merges required content with one or more of the seven science practices (SP), and one activity or lab can encompass several learning objectives. The learning objectives and science practices from the Curriculum Framework that pertain to hormones and endocrine systems are shown in the table below. Note that other learning objectives may apply as well. LO 2.15 The student can justify a claim made about the effect(s) on a biological system at the molecular, physiological or organismal level when given a scenario in which one or more components within a negative regulatory system is altered. LO 2.16 The student is able to connect how organisms use negative feedback to maintain their internal environments. LO 2.17 The student is able to evaluate data that show the effect(s) of changes in concentrations of key molecules on negative feedback mechanisms. LO 2.18 The student can make predictions about how organisms use negative feedback mechanisms to maintain their internal environments. LO 2.19 The student is able to make predictions about how positive feedback mechanisms amplify activities and processes in organisms based on scientific theories and models. LO 2.20 The student is able to justify that positive feedback mechanisms amplify responses in organisms. LO 2.21 The student is able to justify the selection of the kind of data needed to Mader, Biology, 12 th Edition, Chapter

5 answer scientific questions about the relevant mechanism that organisms use to respond to changes in their external environment. LO 2.35 The student is able to design a plan for collecting data to support the scientific claim that the timing and coordination of physiological events involve regulation. LO 2.36 The student is able to justify scientific claims with evidence to show how timing and coordination of physiological events involve regulation. LO 2.37 The student is able to connect concepts that describe mechanisms that regulate the timing and coordination of physiological events. LO 3.31 The student is able to describe basic chemical processes for cell communication shared across evolutionary lines of descent. LO 3.32 The student is able to generate scientific questions involving cell communication as it relates to the process of evolution. LO 3.33 The student is able to use representation(s) and appropriate models to describe features of a cell signaling pathway. LO 3.34 The student is able to construct explanations of cell communication through cell-to-cell direct contact or through chemical signaling. LO 3.35 The student is able to create representation(s) that depict how cell-to-cell communication occurs by direct contact or from a distance through chemical signaling. LO 3.37 The student is able to justify claims based on scientific evidence that changes in signal transduction pathways can alter cellular response. LO 3.38 The student is able to describe a model that expresses key elements to show how change in signal transduction can alter cellular response. LO 3.39 The student is able to construct an explanation of how certain drugs affect signal reception and, consequently, signal transduction pathways. Key Concepts Summary The role of hormones Along with the nervous system, the endocrine system coordinates the activities of the body s other organ systems and helps maintain homeostasis. The hormones secreted by endocrine glands travel through the bloodstream and interstitial fluid to reach their target tissues. Sensory receptors detect changes in the internal and external environments and transmit that information to the CNS, which responds by stimulating muscles and glands. Hormones influence almost every basic homeostatic function of an organism, including metabolism, growth, reproduction, osmoregulation, and digestion. Only certain cells, called target cells, can respond to a specific hormone. A hormone may be a first messenger causes a change in a cell that produces a second messenger that sets the metabolic machinery in motion. 558 Mader, Biology, 12 th Edition, Chapter 40

6 Chemical signals that influence the behavior of other individuals are called pheromones. Components of the endocrine system Only the adrenal cortex, the ovaries, and the testes produce steroid hormones. A portion of the brain, the hypothalamus, helps regulate the body s internal environment through the autonomic nervous system by influencing the heartbeat, blood pressure, appetite, body temperature, and water balance. o It also controls the glandular secretions of the pituitary gland. o Neurosecretory cells of the hypothalamus produce antidiuretic hormone (ADH) and oxytocin which are stored in the posterior pituitary. o The hypothalamus controls the anterior pituitary by producing hypothalamic-releasing hormones and in some instances hypothalamicinhibiting hormones. o Stress of all types, including both emotional and physical trauma, prompts the hypothalamus to stimulate both portions of the adrenal glands. o The adrenal cortex is also involved in regulating the salt and water balance, as well as secreting a small amount of male and female sex hormones. o Meanwhile, the adrenal medulla secretes epinephrine (adrenaline) and norepinephrine (noradrenaline) into the bloodstream to continue the response to stress. o The hypothalamus stimulates the anterior pituitary to produce ACTH, which in turn causes the adrenal cortex to secrete glucocorticoids. Glucocorticoids are involved in the regulation of blood glucose levels. The rise in blood glucose is beneficial to an animal under stress, because glucose is the preferred energy source for neurons. The anterior pituitary releases some hormones that stimulate other endocrine glands to release their hormones. o Gonadotropic hormones stimulate the gonads the testes in males and the ovaries in females to produce gametes and sex hormones. o Adrenocorticotropic hormone (ACTH) stimulates the adrenal cortex to produce cortisol. o Thyroid-stimulating hormone (TSH) stimulates the thyroid to produce thyroxine (T4) and triiodothyronine (T3). o Anterior pituitary also secretes direct acting hormones such as prolactin (stimulates milk production), melanocyte-stimulating hormone (MSH) in amphibians and fish, and growth hormone (GH) that promotes skeletal and muscular growth. o The pituitary gland secretion of follicle-stimulating hormone (FSH) and luteinizing hormone (LH). Cells in the pancreas produce and secrete the hormones insulin and glucagon directly into the blood to regulate blood glucose levels. The testes are located in the scrotum, and the ovaries are located in the pelvic cavity. Mader, Biology, 12 th Edition, Chapter

7 o The testes produce androgens (e.g., testosterone), the male sex hormones. o The ovaries produce estrogens and progesterone, the female sex hormones. The pineal gland produces melatonin that is involved in our sleep-wake cycles. The lobules of the thymus are lined by epithelial cells that secrete hormones called thymosins. These hormones aid in the differentiation of T lymphocytes packed inside the lobules. Leptin is a peptide hormone produced by adipose tissue throughout the body. Leptin acts on the hypothalamus, where it signals satiety, or fullness. Kidneys secrete erythropoietin (EPO) in response to a low blood oxygen level. EPO stimulates the production of red blood cells in the red bone marrow Key Terms adrenal cortex adrenal glands adrenal medulla adrenocorticotropic hormone (ACTH) aldosterone anabolic steroids androgens anterior pituitary antidiuretic hormone (ADH) atrial natriuretic hormone (ANH) calcitonin chemical signals circadian rhythms cortisol cyclic adenosine monophosphate (camp) endocrine glands endocrine system epinephrine erythropoietun (EPO) estrogens exocrine glands exophthalmos first messenger glucagon glucocorticoids gonadotropic hormones growth hormone (GH) hormones hyperthyroidism hypothalamic-inhibiting hormones hypothalamic-releasing hormones hypothalamus hypothyroidism insulin leptin melanocyte-stimulating hormone (MSH) melatonin mineralocorticoids negative feedback norepinephrine ovaries oxytocin pancreas pancreatic islets parathyroid glands parathyroid hormone (PTH) peptide hormones pheromones pineal gland pituitary gland positive feedback posterior pituitary progesterone prolactin (PRL) prostaglandins second messanger steroid hormones testes testosterone thymus thyroid gland thyroid-stimulating hormone (TSH) thyroxine 560 Mader, Biology, 12 th Edition, Chapter 40

8 Teaching Strategies Class time: Three 45-minute class periods Day 1: Lecture on positive and negative feedback mechanisms 20 minutes Activity1, assign students to their group and organ and have student groups complete a generic feedback mechanism chart for the organ that they will be researching 25 minutes Days 2 and 3: Completion and presentation of Activity 1 Suggested Approaches There are many adrenal glands and even more hormones that are produced to regulate metabolism and maintain homeostasis. Students should not memorize all of this information. An understanding of positive feedback control mechanisms and negative feedback control mechanisms should be the focus point. Have students participate in group work to become knowledgeable about one endocrine organ. Activity 1 provides the details for this. Students should recognize positive and negative feedback mechanisms and both will be represented in the project work. The first part of Activity 1 provides generic template for feedback mechanisms that students should use to help explain the functioning of their assigned organ. Mader, Biology, 12 th Edition, Chapter

9 Suggested Activities Activity 1: Endocrine Organ Project Divide students into groups of 4 or 5. Assign each group a different organ from the endocrine system: pancreas, posterior pituitary, anterior pituitary, thyroid, parathyroid, adrenal gland, gonads. Have students generate a feedback mechanism chart for their responses their endocrine organ is involved in. Control center Increase is detected Decrease Set Point Normal Range Decrease is Increase because 6 Control center Each group will research and report back to the class: What is the significance of signals that are received by this organ and where do these signals originate? What types of signals are initiated by your organ l(s) and what is their target? What is the specific signal transduction pathway and what is the desired response? They should report on one disease that affects this organ and describe a day in the life of a teenager with this disease. 562 Mader, Biology, 12 th Edition, Chapter 40

10 Student Edition Chapter Review Answers Answers to Assess Questions 1. e; 2. b; 3. c; 4. a; 5. d; 6. c; 7. a; 8. c; 9. d; 10. b; 11. d; 12. b; 13. b; 14. a; 15. d Answers to Applying the Big Ideas Questions 1. Typically, when blood becomes too concentrated with salt, ADH (antidiuretic hormone) signals the kidneys to reabsorb water instead of losing it in urine in order to conserve water in the body. As a negative feedback mechanism, ADH release by the pituitary gland is stopped as the blood becomes dilute. In some people with nephrogenic diabetes insipidus, mutations in the ADH receptor gene have been found. Support the claim that alterations in the mechanisms of negative feedback can affect biological systems at the molecular and organismal level using at least TWO pieces of evidence from the ADH scenario and what you know about negative feedback systems. Essential Knowledge Science Practice Learning Objective 2.C.1: Organisms use feedback mechanisms to maintain their internal environments and respond to external environmental changes. 6.1: The student can justify claims with evidence. 2.15: The student can justify a claim made about the effect(s) on a biological system at the molecular, physiological or organismal level when given a scenario in which one or more components within a negative regulatory system is altered. 2 points maximum. Evidence for how alterations in the mechanisms of negative feedback can affect biological systems at the molecular level (1 point each): If the ADH receptor gene has a mutation, this could mean that the receptor could not form and fold properly and may be discarded, or it may be denatured and not able to function properly. Even if ADH is released by the pituitary gland, the ADH signal will not be received and the kidneys will not reabsorb water. If the kidneys do not reabsorb water, the blood will not become dilute and the ADH signal will not be shut off by the negative feedback mechanism. Evidence for how alterations in the mechanisms of negative feedback can affect biological systems at the organismal level may include (1 point each): If the ADH signal is not received and the blood is not reabsorbed by the kidneys, much water will be lost in excessive urine production. This could lead to dehydration of the organism. Mader, Biology, 12 th Edition, Chapter

11 Too many salts concentrated in the bloodstream because there is no signal to dilute the blood could lead to changes in blood pressure, kidney failure, seizures and in extreme cases, death because the blood stream is connected to all body tissues. 2. Insulin form the pancreas lowers blood glucose levels by stimulating the uptake of glucose by cells in the liver, muscle and adipose tissue, making it a strong example of a chemical signal that travels a long distance to the target cell. Create a representation hat depicts how cell-to-cell communication occurs from a distance through chemical signaling in the case of insulin. Essential Knowledge Science Practice Learning Objective 3.D.2: Cells communicate with each other through direct contact with other cells or from a distance via chemical signaling. 1.1: The student can create representations and models of natural or man-made phenomena and systems in the domain. 3.35: The student is able to create representation(s) that depict how cell-to-cell communication occurs by direct contact or from a distance through chemical signaling. 3 points maximum. Representations of cell-to-cell communication through the chemical signal insulin may include (1 point each): Any images are clearly labeled, the path traveled by insulin is clearly depicted, and explanations are included. In the presence of high blood glucose, such as is present after eating, the pancreas (in the abdomen) secretes insulin into the blood. Students may even acknowledge that the Islets of Langerhans in the pancreas produce the hormone. Then insulin goes to the liver (in the abdomen), signaling it to store glucose as glycogen. Insulin can go to muscle cells (throughout the body) which store glycogen and build protein. Insulin can go into adipose (fat) tissue where glucose from blood can be used to form fat. Due to the functioning of these three targets, blood glucose level lowers. 564 Mader, Biology, 12 th Edition, Chapter 40

12 Answers to Applying the Science Practices Questions Think Critically 1. Student representations may resemble the pathway illustrated in the figure, but should include labels for the hormones depicted in the Cushing disease scenario. ACTH is the steroid hormone signal that passes through the membrane of the target cell. It then binds with a specific receptor in the cytoplasm, and then travels into the nucleus to bind to another specific receptor on the chromatin. The hormonereceptor complex stimulates the production of messenger RNA that codes for the production of the cortisol hormone. In the case of Cushing disease, many molecules of ACTH at the start of the pathway and of cortisol at the end of the pathway should be represented as opposed to only one as in the given figure. 2. While there are a number of tests conducted by doctors, answers by students may include: a. Confirm that the end product of the pathway is being produced in excess, that too much cortisol being produced. (Doctors can confirm this with a 24-hour urine cortisol or by checking salivary cortisol levels in the early morning and late at night.) If there is more cortisol than is considered normal, Cushing disease could be present. b. Confirm that the hormone that stimulates the pathway is present in excess, that too much ACTH is being produced. (Doctors can confirm this with a blood test.) If greater than normal amounts of ACTH are present, this could be resulting in too much cortisol and Cushing disease could be present. c. Use MRI to determine the presence of a pituitary adenoma (tumor). If there is a tumor present, it could impact hormone regulation of all hormones impacted by the pituitary gland. The most thorough answers will recognize that these three tests would be most effective in determine the presence of Cushing disease if conducted together, as they test for potential causes of the results of the other tests. Mader, Biology, 12 th Edition, Chapter

13 Additional Questions for AP Practice 1. Explain how the parathyroid glands regulate blood calcium levels. 2. The human endocrine system works to maintain homeostasis in the amount of sugar available in our blood. Insulin is released to lower blood sugar levels and glucagon is used to raise blood glucose levels. Select the scenario that correctly represents an alteration of the negative regulatory portion of glucose regulation. A) Glucagon is released into the bloodstream to signal liver cells to take in glucose and lower the blood glucose level. B) Glucagon is released into the blood stream to signal liver cells to take up glucose from the blood stream to increase blood glucose levels. C) Insulin is released into the blood stream to signal liver cells to take up glucose from the blood stream. D) Insulin is released into the blood stream to signal liver cells to release insulin into the blood stream. 566 Mader, Biology, 12 th Edition, Chapter 40

14 Answers Additional Questions for AP Practice 1. Parathyroid hormone (PTH) produced by the parathyroid glands, causes the blood calcium level to increase and the blood phosphate (HPO42 ) level to decrease. Low blood calcium stimulates the release of PTH, which promotes the activity of osteoclasts, releasing calcium from the bones. PTH also promotes the kidneys reabsorption of calcium, lessening its excretion. In the kidneys, PTH also brings about activation of vitamin D. Vitamin D, in turn, stimulates the absorption of calcium from the small intestine. These effects bring the blood calcium level back to the normal range, and PTH secretion stops. When the blood calcium (Ca2+) level is high, the thyroid gland secretes calcitonin. Calcitonin promotes the uptake of Ca2+ by the bones, and therefore the blood Ca2+ level returns to normal. Calcitonin and PTH are therefore considered to be antagonistic hormones, because their action is opposite one another and both hormones work together to regulate the blood calcium level. 2. The correct answer is C. Mader, Biology, 12 th Edition, Chapter