Chapter 014
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  • The endocrine system and its hormones help regulate metabolic processes involving carbohydrates, proteins, and fats. Can you think of other roles the endocrine system plays? <br /> Hormones also play an important role in growth and reproduction. They also help regulate water and electrolyte balance and help the body meet the demands of infection, trauma, and stress. <br />
  • Why does the slide show the gland shooting an arrow at several organs? <br /> The gland secretes a hormone that is directed toward a target organ. Most hormones affect several organs. <br /> What are the two types of hormone receptor sites? <br /> They are membrane receptors and intracellular receptors. <br /> How is the specificity of the receptors like a lock and key? <br /> Each receptor has a specific shape into which only certain hormones can fit. <br /> A particular hormone is circulating in the blood. Why are some organs unaffected by it? <br /> The unaffected organs lack the receptors for that particular hormone. <br />
  • Negative and positive feedback control are discussed on following slides. <br /> What are some examples of biorhythms? <br /> Students might mention the female menstrual cycle and the effects of jet lag. <br /> Some drugs, such as steroids, are administered on a schedule in step with the body’s natural biorhythm. <br /> CNS controls the secretion of hormones in two ways: activation of the hypothalamus and stimulation of the sympathetic nervous system. The hypothalamus controls the pituitary gland, which is discussed on a later slide. <br />
  • Many hormones are controlled by negative feedback, for example, cortisol. <br /> What happens to ACTH secretion when inhibition is relieved? <br /> ACTH secretion increases, thereby stimulating the adrenal gland to secrete more cortisol. This is an example of negative feedback control. <br /> Chapter 1 explained negative control with an analogy of a thermostat controlling temperature; when a room gets hot enough, the thermostat shuts off the furnace. <br />
  • To induce labor in some mothers, IV oxytocin is administered. This initiates a positive feedback loop that ultimately leads to delivery. <br /> Another example of control by positive feedback is activation of the blood clotting mechanism. Once the mechanism is started, clotting factors are sequentially activated until bleed stops. <br />
  • The hypothalmus controls the anterior pituitary by releasing hormones. There are specific releasing hormones for each hormone of the anterior pituitary. For example, CRH—corticotropin-releasing hormone—stimulates the release of ACTH by the anterior pituitary. <br /> What is the name of the capillaries that connect the anterior pituitary to the hypothalamus? <br /> These capillaries are called the hypothalamic-hypophyseal portal system. <br /> Why is there no similar portal system in the posterior pituitary? <br /> The posterior pituitary is nervous tissue because it is a direct extension of the hypothalamus.   <br /> A stalk of tissue attaches the pituitary gland to the undersurface of the hypothalamus. <br />
  • Why is the anterior pituitary called the adenohypophysis and the posterior pituitary is called the neurohypophysis? <br /> The anterior pituitary is composed of glandular tissue (adeno = glandular). The posterior pituitary is a direct extension of the hypothalamus, which is nervous tissue. <br /> Releasing hormones from the hypothalamus reach the adenohypophysis through the portal capillaries. The posterior pituitary does not need releasing hormones. <br />
  • The anterior pituitary secretes at least six hormones that are aimed at their respective target organ, causing the organ to secrete hormones. There are other hormones, described later, that are not controlled by the pituitary gland, for example, insulin. <br /> Why do some people call the anterior pituitary the master gland but others call the hypothalamus the master gland? <br /> The anterior pituitary secretes six hormones that control many glands. The hypothalamus controls the anterior pituitary. <br /> Predict some possible consequences of surgically removing the anterior pituitary. <br /> There will be diminished or absent function in each of the target organs. Hormone replacement therapy is necessary. For instance, supplementation by cortisol compensates for the lack of ACTH. <br />
  • What are the target organs for oxytocin and ADH? <br /> The target organs for oxytocin are the uterus and the breasts. The target organ for ADH is the kidney. The functions or each are described in detail in later chapters. <br />
  • Why may an enlarged thyroid gland be palpable or be visible? <br /> It is located in the neck, anterior to the trachea, right under the skin. <br />
  • T4 is also called thyroxin. <br /> Ask students to predict some consequences of hyposecretion of thyroid hormones. <br /> Answers will include slowed down heart rate, constipation, lack of energy, and weight gain. <br /> What would you expect from hypersecretion of thyroid hormones? <br /> Answers will include a speeded up heart rate, diarrhea, excess energy, weight loss, and exophthalmia. <br /> All thyroid hormone drugs will be T3, T4, or a mixture of the two. <br />
  • What happens if a pregnant woman takes an antithyroid drug, such as propylthiouracil? <br /> The baby will have a deficiency of thyroid hormones and may develop cretinism. This condition is marked by extreme delays in physical and intellectual growth. <br /> Explain why extreme exophthalmia may cause corneal ulceration. <br /> The eyelids cannot cover the bulging eyes, so the cornea dries out, ulcerates, and scars. Early treatment is essential. <br />
  • TRH, or thyrotropin releasing hormone, begins sequence of events leading to the release of T3/T4. <br /> How is secretion of T3 and T4 controlled through negative feedback? <br /> TSH stimulates the thyroid gland to secrete T3 and T4. T3 and T4 shut down further secretion of TSH by the anterior pituitary. <br /> Explain the negative feedback effect of T3 and T4 on the hypothalamus. <br /> Elevations of T3 and T4 suppress hypothalamic-releasing hormone. This suppresses further secretion of TSH by the anterior pituitary. <br />
  • How does the negative feedback loop help explain why iodine deficiency can lead to a goiter? <br /> If you have a lack of iodine, you may not make sufficient thyroid hormones. The negative feedback control fails, resulting in a persistent secretion of TSH. The thyroid gland is continually stimulated by TSH and enlarges (a goiter). <br /> Why is iodized salt commonly used? <br /> The use of iodized salt ensures an adequate intake of iodine and prevents the formation of goiter. The “goiter belts” in this country attest to the importance of adequate dietary iodine. <br />
  • PTH from the parathyroid and calcitonin from the thyroid regulate blood calcium levels within very narrow limits. The parathyroid hormone (PTH) is the most important hormone in this regulatory process. <br />
  • PTH has three target organs, bones, kidney, and intestine. <br /> Ask students to trace the negative feedback loop controlling secretion of PTH. <br /> The stimulus for PTH release is declining levels of calcium in the blood. When PTH is secreted, it stimulates the target organs, thereby raising plasma calcium levels and shutting off further stimulation of PTH. This loop is independent of the hypothalamus and pituitary glands. <br /> Resorption refers to the process whereby osteoclastic activity moves calcium from the bone to the blood. Resorption should not be confused with reabsorption. <br /> In the blood, calcium and phosphate exist in inverse levels; as one rises, the other falls. Drinking large amounts of carbonated soft drinks raises phosphate levels and lowers calcium levels in the blood. Under the influence of PTH, the bones will send calcium to the blood. The long-term effect of this can be softened bones, also called osteomalacia. <br />
  • Why does osteoblastic activity lower levels of blood calcium? <br /> Osteoblastic activity moves calcium from the blood and deposits it in the bone. <br />
  • Hyposecretion of PTH is both more serious and more common than hypersecretion. <br /> Calcium normally stabilizes nerve and muscle membranes; therefore, a deficiency can cause sustained or tetanic contractions of muscles with carpal spasm. Tetany, more seriously, affects the larynx and breathing apparatus. Patients with this condition will become unable to breathe. <br /> Explain why “bones, stone, moans, and groans” are caused by hypercalcemia. <br /> All these effects are caused by calcium leaving the bones and being deposited in other organs, such as the kidney. <br />
  • The adrenal glands secrete two entirely different hormones with different effects. <br />
  • The most important structures to note here are the outer cortex and inner medulla. <br />
  • Epinephrine and norepinephrine prolong the fight-or-flight response of the central nervous system. <br /> A tumor of the adrenal medulla is called pheochromocytoma. What are some likely clinical effects of this tumor? <br /> The presenting and life-threatening sign is severe hypertension; other sympathetic effects will be present. A measurement of urinary catecholamine levels is used in diagnosing pheochromocytoma. <br />
  • “Sugar, salt, and sex” is an easy way to remember the three classes of steroids from the adrenal cortex. In a general way, the classifications reflect the steroids. <br />
  • Glucocorticoids control glucose but also have a profound effect on protein and fat. Use of these steroids as drugs (e.g., prednisone) interferes with normal metabolic pathways so that they resemble those of a diabetic. <br /> Why does aldosterone affect blood volume? <br /> Too little aldosterone decreases reabsorption of salt and water by the kidneys, thereby lowering blood volume. Excess aldosterone has the opposing effect. <br /> Spironolactone blocks aldosterone. Why does this drug exert diuretic effects? <br /> The drug blocks sodium and water reabsorption by the kidney, causing much sodium and water to be eliminated in the urine (diuresis). <br /> During the use spironolactone, clinicians monitor the blood for hyperkalemia. Why might hyperkalemia develop? <br /> Normally aldosterone excretes potassium. Blocking aldosterone can cause the retention of potassium in the blood. <br /> Three virilizing effects are low voice, male hair distribution, and larger bones and muscles. <br />
  • What hormones are undersecreted in Addison’s disease? <br /> Cortisol, aldosterone, and testosterone are undersecreted. <br /> Why might a patient in acute adrenal cortical insufficiency develop adrenal shock? <br /> A deficiency of aldosterone causes diuresis, low blood volume, low blood pressure, and shock. <br /> Why does the patient with Cushing’s syndrome have a moon face and a buffalo hump? <br /> Cortisol causes a redistribution of fat and retention of fluid. <br />
  • Have students describe negative feedback of cortisol secretion. <br /> As cortisol levels rise, the cortisol suppresses the anterior pituitary, thereby decreasing the secretion of ACTH and the adrenal secretion of cortisol. <br /> Why would a sudden discontinuance of prednisone cause an acute adrenal cortical insufficiency? <br /> Long-term use of prednisone suppresses adrenal cortical activity; therefore, when the drug is suddenly withdrawn, the gland is not able to respond and produce cortisol. Discontinuation of steroids always involves tapered doses. <br />
  • The hormones are secreted by the islets of Langerhans. The beta cells of the islets of Langerhans secrete insulin, whereas the alpha cells of the islets of Langerhans secrete glucagon. <br /> It is noteworthy that one organ, the pancreas, secretes the hormones that increase and decrease blood glucose levels. <br />
  • Pancreatic function does not depend upon the anterior pituitary. <br /> What is the stimulus for the release of insulin? <br /> Rising blood glucose levels stimulate the release of insulin. <br /> What is the stimulus for the release of glucagon? <br /> Falling blood glucose levels stimulate the release of glucagon. <br /> Have students describe the negative feedback between glucose and insulin. <br /> As blood glucose rises, insulin is secreted. Insulin lowers blood glucose levels to normal, thereby eliminating the stimulus for its release. The feedback for glucagon is similar. <br /> Remember “pig”: pancreas, insulin, glucagon. <br />
  • Insulin fosters the cellular use of glucose for fuel. With the exception of glucose breakdown, insulin drives the metabolic pathways in the direction of synthesis. <br />   <br />
  • Insulin deficiency causes diabetes mellitus. Without insulin, glucose is not transported into the cell, the cell does not use glucose as fuel, protein is converted to glucose (gluconeogenesis), and fats are converted to ketone bodies. <br />
  • The symptoms of diabetes arise from hyperglycemia and rapid and uncontrolled fatty acid breakdown. For example, in the hyperglycemia column, we see that hyperglycemia progresses to dehydration and shock. <br /> Rapid and uncontrolled fatty acid breakdown results in diabetic ketoacidosis (DKA) and its compensatory mechanisms. One important compensatory mechanism is Kussmaul respirations, which help restore normal blood pH. <br />
  • This slide reviews the effect of hormones on the blood glucose level. Insulin is the only hormone to lower the blood glucose level. <br />   <br />
  • Obesity has several negative hormonal effects. Some cytokines narrow blood vessels, cause inflammation, stimulate blood clotting, secrete estrogen (a hormone that has been linked to several types of cancer), and secrete hormones that are antagonistic to insulin. <br />
  • Most organs in the body secrete their own hormones. These will be discussed as each organ is discussed. For example, the renin-angiotensin-aldosterone system functions with the kidney in regulating blood volume and blood pressure. <br /> How do aspirin and ibuprofen work? <br /> Aspirin and ibuprofen block the synthesis of prostaglandins, which enhance the inflammatory response and increase the sensitivity of nerve endings to pain. <br />

Chapter 014 Presentation Transcript

  • 1. The Human Body in Health and Illness, 4th edition Barbara Herlihy Chapter 14: Endocrine System
  • 2. Lesson 14-1 Objectives • List the functions of the endocrine system. • Define hormone. • Explain negative and positive feedback control loops as regulators for hormone levels. • Describe the relationship of the hypothalamus to the pituitary gland. • Describe the location, hormones, and regulation of the pituitary gland. Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights reserved. 2
  • 3. Endocrine Glands • Ductless glands • Secrete hormones • Widely distributed throughout the body Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights reserved. 3
  • 4. Hormones • Chemical messengers that influence or control activities of other tissues and organs • Classification – Proteins (and protein-related substances) – Steroids Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights reserved. 4
  • 5. Hormones and their Receptors • Gland aims hormone at target organs • Hormone activates receptors – On cell membrane – Within cell nucleus Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights reserved. 5
  • 6. Control of Hormonal Secretion • Feedback control – Negative – Positive • Biorhythms – Circadian and monthly • Central nervous system – Psychoneuroendocrinology Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights reserved. 6
  • 7. Control by Negative Feedback Loop • Example: As level of cortisol rises in the blood to needed level, cortisol shuts off further secretion of ACTH. • As level of cortisol drops, inhibition is relieved. Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights reserved. 7
  • 8. Control by Positive Feedback Loop • A bodily change stimulates further change in the same direction. • The following are some examples. − During labor, pressure of baby’s head on cervix stimulates release of oxytocin. − Oxytocin stimulates uterine contraction, further increasing pressure on cervix. − More oxytocin is released until delivery. Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights reserved. 8
  • 9. Hypothalamus and Pituitary Gland • Hypothalamus controls pituitary function. • Connected to anterior pituitary through capillaries and to posterior pituitary through tissue extension Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights reserved. 9
  • 10. Pituitary Gland: Two Parts • Anterior pituitary – Adenohypophysis – Controlled by releasing hormones of hypothalamus • Posterior pituitary – Neurohypophysis – Extension of hypothalamus Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights reserved. 10
  • 11. Hormones of Anterior Pituitary • TSH • ACTH • Growth hormone • Gonadotropins – FSH and LH • Prolactin Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights reserved. 11
  • 12. Hormones of Posterior Pituitary • Oxytocin • ADH Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights reserved. 12
  • 13. Lesson 14-2 Objectives • Identify the major endocrine glands and their hormones. • Explain the effects of hyposecretion and hypersecretion of the major endocrine glands. Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights reserved. 13
  • 14. Thyroid Gland: Hormones • Follicular cells secrete T3 and T4 into colloid for storage. • FSH releases T3, T4 into the blood. • Parafollicular cells secrete calcitonin. Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights reserved. 14
  • 15. Thyroid Hormones: Functions • T3 and T4 – Regulate metabolism – Permit proper functioning of all other hormones – Promote normal maturation of the nervous system – Promote normal growth and development • Calcitonin – Helps regulate calcium levels in the blood Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights reserved. 15
  • 16. Abnormal Thyroid Secretion • Hypothyroidism: Deficiency of T3/T4, resulting in a slowed down metabolic rate or myxedema • Hyperthyroidism: Excess of T3/T4, causing accelerated metabolic rate or Graves’ disease Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights reserved. 16
  • 17. Control of T3 and T4 Secretion Releasing hormone (TRH) TSH T3 and T4 Negative feedback loop by T3 and T4 Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights reserved. 17
  • 18. Thyroid Gland and Iodine T3 = triiodothyronine T4 = tetraiodothyronine (thyroxine) • Iodine essential for synthesis of T3 and T4 • Iodine deficiency causes goiter or enlargement of thyroid gland. – Iodine deficiency interferes with negative feedback loop Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights reserved. 18
  • 19. Four Parathyroid Glands • Lie along posterior wall of thyroid gland • Are most important regulator of blood calcium • Secrete parathyroid hormone (PTH), which elevates blood calcium level Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights reserved. 19
  • 20. PTH Raises Blood Calcium • Three mechanisms – Bone • Resorption • Kidney – Reabsorbs Ca2+ from urine • Intestine – Absorbs dietary Ca2+ Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights reserved. 20
  • 21. Calcitonin and Blood Calcium • Thyroid gland secretes calcitonin in response to elevated blood calcium level. • Calcitonin lowers blood calcium level – By bone by stimulating osteoblastic activity – By kidney by excreting excess calcium Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights reserved. 21
  • 22. Parathyroid Glands: Abnormal Secretion • Hyposecretion: Hypocalcemic tetany, causing carpal spasm • Hypersecretion: Hypercalcemia • “Bones, stones, moans, and groans” Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights reserved. 22
  • 23. Adrenal Glands • Located above kidneys • Adrenal medulla – Inner region – Secretes catecholamines • Adrenal cortex – Outer region – Secretes steroids Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights reserved. 23
  • 24. Adrenal Glands: Medulla and Cortex Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights reserved. 24
  • 25. Adrenal Medulla • Extension of sympathetic nervous system • Fight-or-flight response – Increases heart rate and blood pressure – Mobilizes body for emergencies • Catecholamines – Epinephrine – Norepinephrine Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights reserved. 25
  • 26. Adrenal Cortex: Steroids • Sugar: Glucocorticoids – Cortisol, most important • Salt: Mineralocorticoids – Aldosterone • Sex: Sex hormones – Testosterone, most important Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights reserved. 26
  • 27. Functions of Steroids • Cortisol affects metabolism of carbohydrate, protein, and fat. • Aldosterone stimulates the kidney’s reabsorption of salt and water and excretion of potassium. • Testosterone exerts virilizing effects. Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights reserved. 27
  • 28. Abnormal Secretion of Steroids • Hyposecretion – Addison’s disease – Acute adrenal cortical insufficiency • Hypersecretion – Cushing’s syndrome – Excess use of steroids as drug (prednisone) will cause cushingoid appearance. Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights reserved. 28
  • 29. Cortisol: Negative Feedback Loop Releasing hormone ACTH Cortisol Negative feedback by cortisol Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights reserved. 29
  • 30. Pancreas • Across abdomen • Islets of Langerhans secrete hormones. • Hormones Insulin glucose Glucagon glucose Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights reserved. 30
  • 31. Pancreas Regulates Blood Glucose • Blood glucose level rises, pancreas secretes insulin • Blood glucose level falls, pancreas secretes glucagon Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights reserved. 31
  • 32. Insulin in Normal Metabolism • Carbohydrate – Increased transport of glucose into cell – Use of glucose as fuel – Storage of excess glucose as glycogen • Protein – Stimulation of protein synthesis • Fat – Stimulation of fatty acid synthesis Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights reserved. 32
  • 33. Deficiency of Insulin • Carbohydrate – Decreased transport of glucose from blood to cell – Decreased utilization of glucose as fuel • Protein – Conversion of protein to glucose: gluconeogenesis • Fats – Formation of ketone bodies: Acetone and ketoacids Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights reserved. 33
  • 34. Diabetes Mellitus: Insulin Deficiency or Ineffectiveness Hyperglycemia • • • • • Glucosuria Polyuria/polydipsia Dehydration Low blood volume Shock Rapid Fatty Acid Catabolism • Ketone bodies • Acetone (fruity odor to breath) • Ketoacids • Kussmaul respirations • Diabetic ketoacidosis Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights reserved. 34
  • 35. Hormones and Blood Glucose • Insulin: Only hormone to lower blood glucose level • All other hormones raise blood glucose level. – Glucagon – Cortisol – Epinephrine – Growth hormone Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights reserved. 35
  • 36. Other Glands • Gonads – Testes secrete testosterone. – Ovaries secrete progesterone and estrogen. • Thymus – Secretes thymosins – Affects immune function • Pineal – Secretes melatonin – Affects biological clock • Adipose tissue secretes unhealthy cytokines. Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights reserved. 36
  • 37. Other Hormones • Organ-specific hormones – Secreted by organs such as heart, kidney, digestive organs • Prostaglandins – Secreted by most tissues – Most act locally – Play a role in regulation of smooth muscle contraction, inflammatory response, and pain Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights reserved. 37