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Transcript
CHAPTER 13: ENDOCRINE SYSTEM OBJECTIVES: 1. Explain why the endocrine system is so closely related to the nervous system. 2. Distinguish between an endocrine gland and an exocrine gland. 3. Define the term hormone and explain its general characteristics. 4. Distinguish between a steroidal and non-steroidal hormone, in terms of composition and action. 5. Locate the following endocrine glands (organs) on a diagram: hypothalamus, pituitary, pineal gland, thyroid, parathyroid, thymus, adrenals, pancreas, ovaries, and testes. 6. Name the three endocrine glands (see above) that are actually divided into two endocrine glands with different functions. 7. For each of the glands listed in #5 & #6 above, name the hormone(s) they secrete, identify the target organ of each hormone, and the effect of each hormone. 8. Name the "master" of the anterior pituitary gland. 9. Define the term gonadotropin, name the two gonadotropins secreted by the anterior pituitary gland, and distinguish between them according to their actions. 10. Explain how the posterior pituitary gland does not produce hormones, but does secrete them. 11. Name the gland that requires iodine to produce most of its hormones. 12. Describe how calcium levels are maintained in the blood. 13. Name the two hormones that work together to regulate water and electrolyte levels in the blood and therefore regulate blood pressure. 14. Describe how glucose levels are maintained in the blood. 15. Explain why the thymus gland decreases in size as we age. 16. Name the gland (hormone) whose production is stimulated by sunlight. 17. Define the term gonad, list the primary gonads in both sexes, and name the hormones that target those gonads. 18. Explain what is meant by "secondary sexual characteristics", name the hormone that causes their development in both sexes, and list target organs. 19. Name the hormones secreted by the ovary, distinguish which particular portion of the ovary secretes each, and name target organs and actions of those hormones. 20. Distinguish between dwarfism, giantism, and acromegaly. 21. Explain why so few cases of cretinism are seen today. 22. Compare and contrast cretinism, myxedema, Grave's Disease, and goiter. 23. Distinguish between Addison's Disease and Cushing's Syndrome. 24. Compare and contrast the two types of the disease Diabetes Mellitus. 25. Describe seasonal affective disorder (SAD) in terms of cause, symptoms, and treatment. I. GENERAL CHARACTERISTICS OF THE ENDOCRINE SYSTEM The general function of the endocrine system is to integrate body systems (i.e. maintain homeostasis), in conjunction with the nervous system. Recall that glands are effectors or responsive body parts that are stimulated by motor impulses from the autonomic nervous system. Some of these glands, endocrine glands compose the endocrine system. See Figure 13.1, page 468. II. A. ENDOCRINE GLAND = a gland that secretes hormones directly into the bloodstream; a ductless gland. B. Exocrine gland = a gland that secretes substances into ducts which then leave the body (i.e. sweat/sebaceous glands) or into a internal space or lumen (i.e. digestive glands). Exocrine glands are not part of the endocrine system! C. HORMONE = a very powerful substance secreted by an endocrine gland into the bloodstream, that affects the function of another cell or "target cell". D. See Fig 13.3, page 469 to see an overview of the endocrine glands. They include the following glands: 1. hypothalamus; 6. thymus; 2. pituitary; 7. adrenals; 3. pineal gland; 8. pancreas; 4. thyroid; 9 . testes; 5. parathyroids; 10. ovaries. HORMONE ACTION A. General Characteristics: 1. needed in very small amounts (potent); 2. produce long-lasting effects in the cells they target; 3. regulate metabolic processes (maintain homeostasis); 4. are regulated by negative-feedback mechanisms; B. Chemistry of Hormones may be steroid (produced from cholesterol = fat-soluble) or non-steroid (watersoluble). See Fig 13.4, page 470. 1. A steroid hormone passes easily through the target cell membrane; 2. A non-steroid hormone requires a receptor on the target cell membrane to allow the hormone to enter the target cell. II. HORMONE ACTION C. Actions of Hormones – alter metabolic activity, only affect cells with receptor 1. Steroid Hormones a. Enter cell by diffusion directly through cell membrane b. Bind to protein receptor c. Newly formed hormone-receptor complex alters gene expression d. New proteins carry out function signaled by hormone 2. Non-steroid Hormones a. Includes amines, peptides, proteins and glycoproteins b. Hormone binds outside of cell and acts as first messenger c. Result is either increase or decrease in some second messenger d. Second messenger activates protein cascade, leading to cellular changes e. Commonly G-protein regulated using cyclic AMP as the second messenger. See Figure 13.6 page 473 and Fig 13.7 page 476. D. Prostaglandins 1. 2. 3. III. locally acting signals (paracrine) varied functions sometimes alter other hormones CONTROL OF HORMONAL SECRETIONS A. Control Sources 1. 2. Generally one or any combination of 3 types of control a. Hormonal control by tropic hormones of hypothalamus b. Nervous control by Autonomic nervous system c. Humoral control by regulating blood levels See Figures 13.10 and 13.11 page 479 for set point and negative feedback The overall scheme for the release of most hormones is presented in Figure 13.15, page 481 in the text. First of all, the HYPOTHALAMUS secretes "releasing hormones" that target the anterior pituitary gland. See Fig 13.12, page 480. IV. GLANDS OF THE ENDOCRINE SYSTEM A. ANTERIOR PITUITARY GLAND (which hangs from the base of the brain and sits in sella turcica (Fig 13.9, page 478) may then secrete 6 different hormones: 1. Human Growth Hormone (HGH) a. controls growth of the body; b. targets bone, muscle and adipose tissue. 2. Prolactin (PRL) a. b. 4. Thyroid stimulating hormone (TSH) a. b. 4. stimulates the production of milk by the mammary glands; targets the mammary glands. controls the secretion of hormones by the thyroid gland; targets thyroid gland. Adrenocorticotropic Hormone (ACTH) a. b. controls the secretion of hormones by the adrenal cortex; targets the outer portion of the adrenal gland (cortex). 5. Follicle Stimulating Hormone (FSH) a. response depends upon sex: o In females, FSH stimulates maturation of an ovarian follicle and ovum; o In males, FSH stimulates the maturation of sperm in the testes; b. A gonadotropin, which targets primary sex organs (ovary & testis). 6. Luteinizing Hormone (LH) a. response depends upon sex: o In females, LH causes ovulation; o In males, LH causes secretion of testosterone. b. A gonadotropin, which targets ovaries & testes. IV. GLANDS OF THE ENDOCRINE SYSTEM B. POSTERIOR PITUITARY GLAND 1. 2. 3. 4. See Fig 13.12, page 480. is located behind the anterior pituitary gland; is continuous with nerve fibers (supraopticohypophyseal tract) of the hypothalamus; does not actually produce hormones (they are produced by the hypothalamus), but stores them until it is stimulated to release them; secretes 2 hormones: See Table 13.6, page 483. a. Antidiuretic Hormone (ADH): o targets distal convoluted tubules (of kidney); o causes DCT’s to reabsorb water back into the bloodstream, and therefore controls water balance and (increases) blood pressure. b. Oxytocin (OT): o targets uterine smooth muscle and breasts; o causes uterine muscle contraction and milk production. c. See Fig 13.17, page 483, comparing the structures of ADH & OT. See Table 13.6, page 485, which summarizes the hormones of the pituitary gland. C. THYROID GLAND: See Fig 13.18 & 13.19, page 486. 1. 2. 3. is located below larynx and around trachea; is involved in iodine uptake (in order to produce thyroxine (T4) & triiodothyronine (T3) below); produces 3 hormones when stimulated by TSH: See Table 13.7, p 487. a. Thyroxine (T4) & Triiodothyronine (T3): o increase basal metabolic rate by stimulating cellular oxygen use to produce ATP; o regulate metabolism o See Fig 13.20, page 486. b. Calcitonin: o release is triggered by an increase in blood calcium levels; o targets bone cells (stimulates osteoblast activity and inhibits osteoclast activity) & distal convoluted tubules (causes secretion of excess calcium into urine); o Therefore, causes a decrease in blood calcium (and phosphate) levels back to normal. IV. GLANDS OF THE ENDOCRINE SYSTEM D. E. PARATHYROID GLANDS: See Fig 13.24 and 13.25, page 489. 1. consist of 4 small glands; 2. are located within the thyroid gland; 3. produce a hormone called Parathyroid Hormone (PTH): a. release of PTH is stimulated by decreased blood calcium levels; b. PTH targets bone cells (activates osteoclasts to resorb bone), proximal convoluted tubules (causes PCT’s to reabsorb calcium back into bloodstream), and small intestine (promotes calcium absorption, See Fig 13.26, page 490). c. Therefore, PTH causes an increase in blood calcium (and phosphate) levels back to normal. 4. PTH and calcitonin together maintain the homeostasis of Ca++ in the blood. a. See Fig 13.26, page 490. ADRENAL GLANDS See Fig 13.28, page 491 and 13.29, page 492. 1. are located atop the kidneys; 2. are divided into an outer adrenal cortex and an inner adrenal medulla. a. Hormones of the Adrenal Medulla: o is located in the central portion of the adrenal glands; o produces 2 closely related hormones, which function in the sympathetic division of the autonomic nervous system: 1. epinephrine; 2. norepinephrine. a. See Fig 13.30, page 492. o These hormones target: 1. the heart (SA Node to increase heart rate); 2. smooth muscle: a. peripheral arterioles (vasoconstriction, which increases blood pressure); b. terminal bronchioles (bronchodilation, which increases depth of breathing) 3. the diaphragm (increased breathing rate). See Fig 13.37, page 501, and Table 13.13, page 501, concerning stress. IV. GLANDS OF THE ENDOCRINE SYSTEM E. ADRENAL GLANDS b. Hormones of the Adrenal Cortex: See Fig 13.28, page 491 and 13.29, page 492. o o o F. PANCREAS: a. b. c. 2. e. See Fig 13.34, page 497. is located behind the stomach on the left side of abdomen; functions as a mixed gland. (i.e. both an exocrine gland (digestion) and endocrine gland (see below); Hormones of the Pancreatic Islets (of Langerhans) See Fig 13.35, page 497, and Table 13.12, page 498. 1. d. is located in the outer portion of the adrenal glands; produces many steroid hormones when stimulated by ACTH: See Fig 13.32, page 494, and table 13.11, page 495. 1. Aldosterone targets proximal convoluted tubules, causing reabsorption of water and electrolytes back into the blood (increases blood pressure). a. See Fig 13.31, page 494. 2. Cortisol targets all cells, where it regulates glucose metabolism (along with T3 and T4). a. See Fig 13.33, page 495. 3. Supplemental sex hormones (estrogens and androgens) that target secondary sex organs. Glucagon: o is produced by Alpha cells (α-cells) in Islets of Langerhans; o Secretion is stimulated by decreased blood glucose levels (i.e. fasting). o increases blood glucose levels (i.e. causes breakdown of glycogen and release of glucose into bloodstream). Insulin: o is produced by Beta cells (β-cells) in Islets of Langerhans; o Secretion is stimulated by increased blood glucose levels (i.e. after eating). o decreases blood glucose levels (i.e. moves glucose from bloodstream into cells and promotes glycogen formation in liver and skeletal muscle). See Fig 13.36, page 498 to review how these two hormones regulate glucose homeostasis in the blood. See Clinical Application 13.4, page 499, Diabetes Mellitus. IV. GLANDS OF THE ENDOCRINE SYSTEM G. THYMUS GLAND: See Fig 16.12, page 615. 1. is located in the mediastinum region behind sternum; 2. produces a hormone called thymosin that affects the maturation of lymphocytes (T-cells); 3. plays an important role in lymphatic system and immunity; 4. decreases in size as we age. H. PINEAL GLAND: See Fig 13.3, page 469. 1. is attached to the thalamus of the brain stem; 2. secretes a hormone called melatonin: a. production is stimulated by daylight (circadian rhythm); b. affects moods, emotions, etc. I. OVARIES: (will be discussed in greater detail in Chapter 22) 1. An ovarian follicle (and ovum) start to mature each month following puberty under the influence of follicle stimulating hormone (FSH). a. The developing follicle secretes estrogen: o Estrogen develops female secondary sexual characteristics (at puberty) and maintains them throughout life. o Estrogen targets: 1. hair follicles in axillary and inguinal regions; 2. mammary glands/ breasts; 3. adipose tissue in hips, thighs, and buttocks. 2. Luteinizing hormone (LH) causes the mature follicle to rupture, releasing the ovum (ovulation). o a. The follicle then becomes the corpus luteum. The corpus luteum secretes progesterone: 1. Progesterone prepares the uterine lining for implantation of the zygote. J. TESTES: 2. (will be discussed in greater detail in Chapter 22) 1. FSH targets the testes and causes the production of sperm. LH targets the testes and causes the production of testosterone: b. a. Testosterone develops male secondary sexual characteristics at puberty and maintains them throughout life. Testosterone targets: o hair follicles in facial axillary and inguinal regions; o muscle and bone; o vocal cords in larynx. V. HORMONE SUMMARY TABLE (Keyed at the end of this outline) HORMONE GH TSH PRL ACTH LH FSH T3/T4 ALDOSTERONE CORTISOL ESTROGEN PROGESTERONE TESTOSTERONE ADH OT PTH CALCITONIN INSULIN GLUCAGON EPINEPHRINE NOREPINEPHRINE MELATONIN THYMOSIN SECRETED BY WHAT GLAND? TARGETS WHAT GLAND OR ORGAN OR TISSUE? EFFECT(S) AT TARGET SITE VI. STRESS AND ITS EFFECTS A. Types of Stress 1. Physical a. Injury = accidental b. Exercise = purposeful 2. B. VII. Responses to Stress 1. General Stress Syndrome is the hypothalamic response to stress 2. Activates adrenal medulla via sympathetic nervous system – short term 3. Activates adrenal cortex (cortisol) release in long term stress 4. Basic goal is to increase available nutrients to fight off stress HOMEOSTATIC IMBALANCES OF THE ENDOCRINE SYSTEM (i.e. abnormal hormonal levels) A. VII. Psychological a. Emotions = automatic b. Overloaded = can be self induced Diabetes Mellitus 1. See introduction on page 468. 2. See Clinical Application 13.4, page 499. 3. Symptoms (3 poly's): polyuria, polydypsia, polyphagia. Two types: a. Type I /IDDM (10%): o absolute insulin deficiency, with insulin administration. o Patients < 20 years; o autoimmune disorder where β-cells are destroyed; o Hyperglycemia results. o Cells can't use glucose so fat is broken down, releasing ketone bodies, causing ketoacidosis, lowering blood pH, and causing death. o Complications include Atherosclerosis, CV disease, IHD, PVD, gangrene, blindness due to cataracts (lens) and retinal vascular disease; renal failure. o Treatments: 1. artificial pancreas that detects fall in glucose levels and automatically releases insulin; 2. transplant of pancreas or Beta cells. b. Type II/NIDDM (90%) o patients > 40 years, o overweight, o hypertension, o Problem is usually with receptors on target cells; o Controlled by diet, exercise, and weight loss; o Drug Diabeta (glyburide) may help stimulate insulin secretion of β-cells (if low levels of insulin is the cause). HOMEOSTATIC IMBALANCES OF THE ENDOCRINE SYSTEM (i.e. abnormal hormonal levels) B. Growth Hormone Imbalances: See Clinical Application 13.2, page 482. 1. Pituitary Dwarfism = hyposecretion of GH during growth years. a. slow bone growth & closing of epiphyseal plates before normal height is reached; b. Treatment = oral GH therapy. 2. Pituitary giantism = hypersecretion of GH during growth years. a. abnormal increase in the length of long bones. 3. Acromegaly = hypersecretion of GH during adulthood. a. Bones of hands, feet, cheeks, and jaw thicken; b. Soft tissues also grow. C. ADH Imbalances: See blue box on page 484. 1. Diabetes insipidus = hyposecretion of ADH. a. diuresis, dehydration, thirst; b. ADH in nasal spray. D. Thyroid Hormone Imbalances: See Table 13.8, page 487. 1. Cretinism = hyposecretion of T3/T4 during fetal life and infancy. See Fig 13.11, page 479. a. dwarfism & mental retardation; b. prevention = newborn testing; c. treatment = oral thyroid therapy. 2. Myxedema = hyposecretion during adulthood. a. edema, slow heart rate, low body temp, dry hair & skin, muscular weakness, lethargy, weight gain; b. Oral thyroid hormones reduce symptoms. 3. Grave's Disease = an autoimmune disorder that causes growth of thyroid and hypersecretion of thyroid hormones, with no negative feedback. a. enlarged thyroid (2-3x larger); b. peculiar edema of the eyes (bulging); c. increased metabolic rate, heat intolerance, increased sweating, weight loss, insomnia, tremor, and nervousness. d. treatment = surgical removal, use of radioisotopes to destroy some of the thyroid. and anti-thyroid drugs to block synthesis of the hormones. e. See Fig 13.22, page 488 and blue box on page 488 re: Bush family. 4. Goiter = low thyroid hormones due to iodine deficiency. a. No thyroid hormones inhibit pituitary release of TSH; b. Thyroid is overstimulated and enlarges, but still functions below normal levels. c. See Fig 13.23, page 488. E. Parathyroid Hormone Imbalances: See Table 13.9, page 490. VII. HOMEOSTATIC IMBALANCES OF THE ENDOCRINE SYSTEM (i.e. abnormal hormonal levels) F. Adrenal Cortical Hormone Imbalances 1. 2. See Clinical Application 13.3, p 496. Addison's Disease = hyposecretion of AC hormones due to autoimmunity or disease (TB). Symptoms: mental lethargy, anorexia, nausea, vomiting, weight loss, pigmentation. Cushing's Syndrome = hypersecretion of AC hormones due to pituitary tumor or steroid administration. Symptoms: redistribution of fat, thin limbs due to wasting of muscles (i.e. protein catabolism), "moon face", "buffalo hump", "beer belly", stretch marks, bruises, poor wound healing, hyperglycemia, osteoporosis, weakness, hypertension, swings. Usual cause: administration of steroids (i.e. prednisone) for transplant patients, asthma, and chronic inflammatory disorders. G. Pineal Gland/ Melatonin Imbalances: See blue box on page 500. VIII. LIFE SPAN CHANGES Endocrine glands tend to shrink and accumulate fibrous connective tissue, fat, and lipofuscin with age, but hormone levels usually remain within normal levels. IX. Innerconnections of the Endocrine System. See page 503. X. Clinical Terms Related to the Endocrine System. See page 504. HORMONE SUMMARY TABLE HORMONE SECRETED BY WHAT GLAND? TARGET(S)? EFFECT(S) AT TARGET SITE Growth Hormone (GH) anterior pituitary bone, muscle, fat growth of tissues Thyroid Stimulating Hormone (TSH) anterior pituitary thyroid secrete hormones Prolactin (PRL) anterior pituitary mammary glands produce milk Adrenocorticotropic hormone (ACTH) anterior pituitary adrenal cortex secrete hormones Luteinizing Hormone (LH) anterior pituitary In males: interstitial cells in testes; in females: mature ovarian follicle males: testosterone secretion females: ovulation Follicle stimulating hormone (FSH) anterior pituitary males: semiiferous tubules of testes; females: ovarian follicle males: sperm production females: follicle/ovum maturation Triiodothyronine (T3) & Thyroxine (T4) thyroid all cells regulates rate of metabolism ALDOSTERONE adrenal cortex Proximal convoluted tubules reabsorption of water and Na (increases blood pressure) CORTISOL adrenal cortex all cells Rate of glucose metabolism ESTROGEN ovarian follicle secondary sex organs development at puberty and maintenance throughout life HORMONE SECRETED BY WHAT GLAND? corpus luteum of ovary TARGET(S)? TESTOSTERONE seminiferous tubules of testes secondary sex organs development and maintenance Anti-Diuretic Hormone (ADH) posterior pituitary distal convoluted tubule (DCT) reabsorption of water ( increases blood pressure) Oxytocin (OT) posterior pituitary uterine smooth muscle contraction during labor Parathyroid Hormone (PTH) Parathyroid Proximal kidney tubules, osteoclasts, intestine reabsorption of Ca++ into blood, bone resorption, dietary Ca ++ absorption (increases blood Ca++) CALCITONIN thyroid Distal convoluted tubules and osteoblasts secretion of Ca++ into urine, bone formation (decreases blood Ca++) INSULIN β-cells of Pancreatic Islets all cells, liver and skeletal muscle pushes glucose into cells from blood, glycogen formation (decreases blood glucose) GLUCAGON α-cells of pancreatic Islets liver and skeletal muscle breakdown of glycogen (increase in blood glucose) EPINEPHRINE/ NOREPINEPHRINE adrenal medulla increases heart rate and blood pressure... MELATONIN pineal cardiac muscle, arteriole and bronchiole smooth muscle, diaphragm, etc limbic system THYMOSIN thymus t-lymphocytes Maturation PROGESTERONE uterine endometrium EFFECT(S) AT TARGET SITE preparation for implantation (thickens, etc) Circadian rhythm, emotions/behavior Chapter 13: Endocrine System I. General Characteristics of the Endocrine System A. The endocrine glands secrete hormones. B. Hormones diffuse from interstitial fluids into the blood stream and eventually act on target cells. C. Paracrine secretions are secretions that do not travel in the blood stream to their targets. D. Autocrine secretions are secretions that affect the secreting cell itself. E. Exocrine glands secrete substances into ducts. F. Endocrine glands and their hormones control metabolic processes. G. Endocrine hormones also play vital roles in reproduction, development, and growth. H. The larger endocrine glands are the pituitary, thyroid, parathyroids, adrenals, and pancreas. II. Hormone Action A. Introduction 1. Hormones only affect their target cells. 2. Target cells have receptors for particular hormones. B. Chemistry of Hormones 1. Introduction a. Steroid hormones are synthesized from cholesterol. b. Nonsteroid hormones are synthesized from amino acids. 2. Steroid Hormones a. Steroids are lipids that include complex rings of carbon and hydrogen atoms. b. Examples of steroid hormones are testosterone, estrogen, aldosterone, and cortisol. 3. Nonsteroid Hormones a. Examples of hormones called amines are norepinephrine and epinephrine. b. Protein hormones are composed of long chains of amino acids. c. Examples of protein hormones are those secreted by the anterior pituitary and parathyroid glands. d. Hormones called glycoproteins are produced by the anterior pituitary. e. Peptide hormones are short chains of amino acids. f. Peptide hormones come from the posterior pituitary and hypothalamus. g. Prostaglandins are paracrine substances and are produced in a wide variety of cells. C. Actions of Hormones 1. Introduction a. Hormones exert their effects by altering metabolic processes. b. Hormones may reach all cells but only affect those that have appropriate receptors. c. The more receptors the hormone binds on its target cell, the greater the response. 2. Steroid Hormones a. Steroid hormones are insoluble in water but are soluble in lipids. b. Steroid hormones can diffuse into cells relatively easily. c. Once steroid hormones are inside a cell, they combine with specific protein receptors located usually in the nucleus. d. The binding of a steroid hormone to its receptor usually activates or inhibits a gene. e. Activated genes code for specific proteins. f. The new proteins may be enzymes, transport proteins, or hormone receptors and they bring about cellular changes. 3. Nonsteroid Hormones a. A nonsteroid hormone usually binds with receptors located on the cell membrane. b. When a nonsteroid hormone binds to a membrane receptor, this causes the receptor’s activity site to interact with other membrane proteins. c. Receptor binding may alter the function of enzymes or membrane transport mechanisms, changing the concentrations of still other cellular components. d. A first messenger is the hormone. e. Second messengers are the chemicals in the cell that induce the changes that are recognized as responses to the hormone. f. Many hormones use cyclic AMP as a second messenger. g. G proteins are activated by the binding of a hormone to a membrane receptor. h. Adenylate cyclase is activated by G proteins. i. Adenylate cyclase functions to form cyclic AMP from ATP. j. Cyclic AMP activates another set of enzymes called protein kinases. k. Protein kinases function to transfer phosphate groups from ATP to proteins substrate molecules. l. Phosphorylated substrates may be converted from inactive to active forms. m. Activated proteins then alter various cellular processes to bring about the effect of that particular hormone. n. Hormones whose actions depend upon cyclic AMP include releasinghormones form the hypothalamus, TSH, ACTH, FSH, LH, ADH, PTH, norepinephrine, epinephrine, glucagon, and calcitonin. o. An example of another second messenger is DAG. p. In another mechanism, a hormone binding to its receptor increases calcium, ion concentration within the target cell. q. Calcium ions bind to the protein calmodulin to activate it. r. Activated calmodulin functions to interact with enzymes, altering their activities. s. Cells are highly sensitive to changes in concentration of nonsteroid hormones because responses to them is greatly amplified through second messengers. D. Prostaglandins 1. Prostaglandins are paracrine substances that act locally. 2. Some prostaglandins regulate cellular responses to hormones. 3. The variety of effects prostaglandins can produce include relaxation of smooth muscle in airway and blood vessels, contraction of smooth muscle in the uterus, stimulation of secretion of various hormones, and promotion of inflammation. III. Control of Hormonal Secretions A. Introduction 1. Hormones are continually excreted in urine and broken down by enzymes in the liver. 2. Increasing or decreasing blood levels of hormones requires increased of decreased secretion. B. Control Sources 1. The hypothalamus controls the anterior pituitary gland’s release of tropic hormones. 2. Tropic hormones are those that stimulate other endocrine gland sto release hormones. 3. An example of an endocrine organ directly stimulated by the nervous system is the adrenal medulla. 4. Some endocrine glands respond to changes in the composition of the internal environment. 5. As a result of negative feedback mechanisms, hormone levels remain relatively stable. IV. Pituitary Gland A. Introduction 1. The pituitary gland is located at the base of the brain. 2. The infundibulum is a stalk that attaches the pituitary gland to the hypothalamus. 3. The two portions of the pituitary are anterior and posterior. 4. The anterior lobe secretes the following hormones: GH, TSH, ACTH, FSH, LH, PRL. 5. The posterior pituitary secretes the following hormones: OT and ADH 6. The hypothalamus controls most of the pituitary gland’s activities. 7. The posterior pituitary receives impulses from the hypothalamus. 8. Releasing hormones from the hypothalamus control the anterior pituitary. 9. The hypophyseal portal veins are vessels that pass downward along the pituitary stalk from the hypothalamus and give rise to a capillary be in the anterior lobe of the pituitary. B. Anterior Pituitary Hormones 1. Somatotropes secrete GH. 2. Mammotropes secrete PRL. 3. Thyrotropes secrete TSH. 4. Corticotropes secrete ACTH. 5. Gonadotropes secrete FSH and LH. 6. Actions of growth hormone are stimulation of cells to enlarge and more rapidly divide, enhance movement of amino acids through the cell membranes, and increases the rate of protein synthesis. GH also decreases the rate as which cells utilize carbohydrates and increases the rate at which cells use fats. 7. The secretion of GH is controlled by somatostatin and GHRH. 8. Actions of prolactin are to sustain mild production after birth and to amplify effect of LH in males. 9. The secretion of PRL is controlled by PIH and PRF. 10. Actions of thyroid-stimulating hormone are to stimulate the thyroid gland to release its hormones. 11. The secretion of TSH is controlled by TRH. 12. The actions of adrenocorticotropic hormone are to control secretion of certain hormone from the adrenal cortex. 13. The secretion of ACTH is controlled by CRH. 14. Gonadotropins are LH and FSH. 15. The actions of follicle-stimulating hormone are to promote development of egg-containing follicles in ovaries, to simulate follicular cells to releases estrogen, and in male, to stimulate production of sperm cells. 16. The actions of luteinizing hormone are to promote secretion of sex hormones and to promote the release egg cells in females. 17. The secretion of FSH and LH is controlled by GnRH. C. Posterior Pituitary Hormones 1. The posterior pituitary consists of nerve fibers and neuroglial cells. 2. Specialized neurons in the hypothalamus produce two hormones called OT and ADH. 3. The hormones produced in the hypothalamus travel down axons through the pituitary stalk to the posterior pituitary. 4. The actions of antidiuretic hormone are to cause a reduction in water excretion, and to raise blood pressure. 5. The secretion of ADH is controlled by blood water concentration and blood volume. 6. The actions of oxytocin are to contact muscles in uterine wall and to contract muscles associated with milk-secreting cells. 7. The secretion of oxytocin is controlled by uterine stretch and stimulation of breasts. V. Thyroid Gland A. Introduction 1. The thyroid gland consists of two lobes. 2. The thyroid gland is located just below the larynx on either side and anterior to the trachea. B. Structure of the Gland 1. Follicles are secretory parts of the thyroid gland. 2. Colloid is a viscous fluid that fills follicles and contains thyroglobulin. 3. Thyroglobulin is a glycoprotein. 4. Extrafollicular cells are located outside of follicles. 5. The follicular cells produce hormones. C. Thyroid Hormones 1. The three hormones produced by the thyroid gland are T4, T3, and calcitonin. 2. The actions of thyroxine and triiodothyronine are to regulate metabolism of carbohydrates, lipids, and proteins. 3. The secretion of T3 and T4 are controlled by TSH. 4. Follicular cells require iodine to produce T3 and T4. 5. The actions of calcitonin are to lower blood calcium levels. 6. The secretion of calcitonin is controlled by blood calcium levels. It is released in response to high blood calcium levels. VII. Parathyroid Glands A. Introduction 1. Parathyroid glands are located embedded in the thyroid gland. 2. Usually a person has four parathyroid glands. B. Structure of the Glands 1. Each parathyroid gland is covered by a thin capsule. 2. The body of a parathyroid gland consists of many tightly packed secretory cells. C. Parathyroid Hormone 1. The actions of PTH are to raise blood calcium levels. 2. The secretion of PTH is controlled by blood calcium levels. It is released in response to low blood calcium levels. VIII. Adrenal Glands A. Structure of the Glands 1. The adrenal glands are shaped like pyramids. 2. The two parts of an adrenal gland are the cortex and medulla. 3. The adrenal medulla consists of irregularly shaped cells grouped around blood vessels. 4. The adrenal cortex is composed of closely packed masses of epithelial layers. 5. The three layers of the adrenal cortex are the outer zona glomerulosa, the middle zona fasciculata, and the inner zona reticulairs. B. Hormones of the Adrenal Medulla 1. The two hormones released by the adrenal medulla are epinephrine and norepinephrine. 2. The actions of epinephrine and norepinephrine are increased heart rate, increased force of cardiac muscle contraction, elevated blood pressure, increased breathing rate and decreased activity of the digestive system 3. The secretion of epinephrine and norepinephrine are controlled by the sympathetic nervous system. C. Hormones of the Adrenal Cortex 1. Introduction a. The adrenal cortex produces more than 30 different steroids. b. The most important adrenal cortical hormones are aldosterone, cortisol, and certain sex hormones. 2. Aldosterone a. Aldosterone is secreted by the zona glomerulosa and is called a mineralocorticoid because it helps regulate the concentration of mineral electrolytes. b. The actions of aldosterone are regulation of concentration of extracellular electrolytes by conserving sodium ions and excreting potassium ions. c. The secretion of aldosterone is controlled by electrolyte concentrations in body fluids and the renin-angiotensin mechanism 3. Cortisol a. Cortisol is secreted by the zona fascilulata and is called a glucocorticoid because it affects glucose metabolism b. The actions of cortisol are to decrease protein synthesis, increase fatty acid release, and simulate glucose synthesis from noncarbohydrates. c. The secretion of cortisol is controlled by CRH. 4. Sex Hormones a. The sex hormones are secreted by the zona reticularis. b. The actions of the sex hormones are to supplement sex hormone from the gonads. c. Examples of sex hormones are androgens such as testosterone. IX. Pancreas A. Structure of the Gland 1. The pancreas is located posterior to the stomach. 2. The endocrine portion of the pancreas consists of islets of Langerhans which are also called pancreatic islets. 3. Three cell types of the pancreatic islets are alpha, beta, and delta. 4. Alpha cells secrete glucagon. 5. Beta cells secrete insulin. 6. Delta cells secrete somatostatin. B. Hormones of the Pancreatic Islets 1. The actions of glucagon are to stimulate the liver to break down glycogen and to convert noncarbohydrates into glucose. It also simulated the breakdown of fats. 2. The secretion of glucagon is controlled by blood glucose concentrations. 3. The actions of insulin are to promote the formation of glycogen from glucose, to inhibit conversion of noncarbohydrates into glucose, and to enhance movement of glucose through adipose and muscle cell membranes. It also decreases blood glucose concentrations, promotes transport of amine acids into cells, and enhances synthesis of proteins and fats. 4. The secretion of insulin is controlled by blood glucose concentrations. 5. The function of somatostatin is to help regulate carbohydrates. X. Other Endocrine Glands A. Pineal Gland 1. The pineal gland is located near the roof of the third ventricle. 2. The pineal gland produces the hormone melatonin. 3. The functions of melatonin are to help regulate circadian rhythms and to inhibit secretion of gonadotropins. B. Thymus gland 1. The thymus gland is located between the lungs. 2. The thymus gland secretes a group of hormones called thymosins. 3. The function of thymosin is to promote the maturation of T lymphocytes. C. Reproductive Organs 1. Reproductive organs that secrete hormones are ovaries and testes. 2. Examples of hormones produced by reproductive organs are estrogen, progesterone, and testosterone. D. Other Hormone-Producing Organs 1. The hormone produced by the heart is ANP. 2. The hormone produced by the kidneys is erythropoietin. XI. Stress and Its Effects A. Introduction 1. A stressor is a factor capable of producing stress. 2. Stress is a protective response produced by the body in response to stress factors. B. Types of Stress 1. Examples of physical stress include extreme cold or heat, decreases oxygen concentrations, infection, injuries, heavy exercise and loud sounds. 2. Examples of psychological stress are imagined dangers, personal losses, unpleasant social interaction or any factor that threatens a person. C. Responses to Stress 1. The general stress syndrome is a group of symptoms produced by the hypothalamus in response to stress. 2. Major events of the general stress syndrome are increased blood glucose levels, increased heart rate and breathing rate, dilation of airways, and shunting of blood into muscles. See table 13.13. XII. Life-Span Changes A. General changes in the glands of the endocrine system are a decrease in size and increase in the proportion of each gland that is fibrous in nature. B. Treatments for endocrine disorders include supplements of hormones or removing part of an overactive gland or using drugs to block the action of an overabundant hormone. C. Levels of ADH increase with age and as a result, the kidneys reabsorb more water. D. The decrease of calcitonin levels with age increases the risk of osteoporosis. E. The most obvious changes in endocrine function involve blood glucose regulation. Chapter 13: Endocrine System I. General Characteristics of the Endocrine System A. The endocrine glands secrete _____________________________________________ B. Hormones diffuse from ________________________ into ______________________ ___________________ and eventually act on __________________________________ C. Paracrine secretions are __________________________________________________ D. Autocrine secretions are _________________________________________________ E. Exocrine glands secrete substances into _____________________________________ F. Endocrine glands and their hormones control _________________________________ ________________________________________________________________________ G. Endocrine hormones also play vital roles in __________________________________ ________________________________________________________________________ H. The larger endocrine glands are ___________________________________________ ________________________________________________________________________ II. Hormone Action A. Introduction 1. Hormones only affect their _________________________________________ 2. Target cells have ________________________ for ______________________ __________________________________________________________________ B. Chemistry of Hormones 1. Introduction a. Steroid hormones are synthesized from __________________________ b. Nonsteroid hormones are synthesized from _______________________ 2. Steroid Hormones a. Steroids are ________________________________________________ b. Examples of steroid hormones are ______________________________ ____________________________________________________________ 3. Nonsteroid Hormones a. Examples of hormones called amines are ________________________ ____________________________________________________________ b. Protein hormones are composed of _____________________________ c. Examples of protein hormones are ______________________________ ____________________________________________________________ d. Hormones called glycoproteins are produced by ___________________ ____________________________________________________________ e. Peptide hormones are ________________________________________ f. Peptide hormones come from __________________________________ ____________________________________________________________ g. Prostaglandins are ____________________________________ and are produced ____________________________________________________ C. Actions of Hormones 1. Introduction a. Hormones exert their effects by ________________________________ ____________________________________________________________ b. Hormones may reach all cells but only affect _____________________ ____________________________________________________________ c. The more receptors the hormone binds on its target cell, the greater ___ ____________________________________________________________ 2. Steroid Hormones a. Steroid hormones are insoluble in ________________________ but are soluble in ____________________________________________________ b. Steroid hormones can diffuse__________________________________ c. Once steroid hormones are inside a cell, they combine with __________ ___________________ located _________________________________ d. The binding of a steroid hormone to its receptor usually ____________ or ____________________________________________________ a gene. e. Activated genes code for _____________________________________ f. The new proteins may be _____________________________________ _____________________________ and they bring about cellular changes. 3. Nonsteroid Hormones a. A nonsteroid hormone usually binds with receptors located __________ ____________________________________________________________ b. When a nonsteroid hormone binds to a membrane receptor, this causes the receptor’s activity site to ____________________________________ c. Receptor binding may alter ___________________________________ ____________________________________________________________ d. A first messenger is _________________________________________ e. Second messengers are _______________________________________ f. Many hormones use _______________________________ as a second messenger. g. G proteins are activated by ___________________________________ h. Adenylate cyclase is activated by ______________________________ i. Adenylate cyclase functions to _________________________________ j. Cyclic AMP activates ________________________________________ k. Protein kinases function to ____________________________________ l. Phosphorylated substrates may be converted from__________________ to active forms. m. Activated proteins then alter __________________________________ ____________________________________________________________ n. Hormones whose actions depend upon cyclic AMP include __________ ____________________________________________________________ o. An example of another second messenger is ______________________ p. In another mechanism, a hormone binding to its receptor increases ____ ____________________________________________________________ q. Calcium ions bind to the protein ____________________ to activate it. r. Activated calmodulin functions to ______________________________ s. Cells are highly sensitive to changes in concentration of nonsteroid hormones because _____________________________________________ ____________________________________________________________ D. Prostaglandins 1. Prostaglandins are ________________________________________________ 2. Some prostaglandins regulate _______________________________________ __________________________________________________________________ 3. The variety of effects prostaglandins can produce include _________________ __________________________________________________________________ III. Control of Hormonal Secretions A. Introduction 1. Hormones are continually _____________________ in urine and broken down _____________________________ in the_______________________________ 2. Increasing or decreasing blood levels of hormones requires ________________ __________________________________________________________________ B. Control Sources 1. The hypothalamus controls _________________________________________ 2. Tropic hormones are ______________________________________________ 3. An example of an endocrine organ directly stimulated by the nervous system is __________________________________________________________________ 4. Some endocrine glands respond to changes in __________________________ __________________________________________________________________ 5. As a result of ________________________________ , hormone levels remain relatively stable. IV. Pituitary Gland A. Introduction 1. The pituitary gland is located ________________________________________ 2. The infundibulum is _______________________________________________ 3. The two portions of the pituitary are __________________________________ 4. The anterior lobe secretes the following hormones: ______________________ __________________________________________________________________ 5. The posterior pituitary secretes the following hormones: __________________ 6. The ______________________ controls most of the pituitary gland’s activities. 7. The posterior pituitary receives impulses from __________________________ 8. ____________________ from the hypothalamus control the anterior pituitary. 9. The hypophyseal portal veins are ____________________________________ __________________________________________________________________ B. Anterior Pituitary Hormones 1. Somatotropes secrete ______________________________________________ 2. Mammotropes secrete _____________________________________________ 3. Thyrotropes secrete _______________________________________________ 4. Corticotropes secrete ______________________________________________ 5. Gonadotropes secrete ______________________________________________ 6. Actions of growth hormone are ______________________________________ __________________________________________________________________ 7. The secretion of GH is controlled by __________________________________ __________________________________________________________________ 8. Actions of prolactin are ____________________________________________ __________________________________________________________________ 9. The secretion of PRL is controlled by _________________________________ __________________________________________________________________ 10. Actions of thyroid-stimulating hormone are ___________________________ __________________________________________________________________ 11. The secretion of TSH is controlled by ________________________________ __________________________________________________________________ 12. The actions of adrenocorticotropic hormone are ________________________ __________________________________________________________________ 13. The secretion of ACTH is controlled by ______________________________ __________________________________________________________________ 14. Gonadotropins are _______________________________________________ 15. The actions of follicle-stimulating hormone are ________________________ __________________________________________________________________ 16. The actions of luteinizing hormone are _______________________________ __________________________________________________________________ 17. The secretion of FSH and LH is controlled by _________________________ __________________________________________________________________ C. Posterior Pituitary Hormones 1. The posterior pituitary consists of ____________________________________ 2. Specialized neurons in the hypothalamus produce two hormones called ______ __________________________________________________________________ 3. The hormones produced in the hypothalamus travel down _________________ __________________________________________________________________ 4. The actions of antidiuretic hormone are _______________________________ __________________________________________________________________ 5. The secretion of ADH is controlled by ________________________________ __________________________________________________________________ 6. The actions of oxytocin are _________________________________________ __________________________________________________________________ 7. The secretion of oxytocin is controlled by ______________________________ __________________________________________________________________ V. Thyroid Gland A. Introduction 1. The thyroid gland consists of ________________________________________ 2. The thyroid gland is located _________________________________________ B. Structure of the Gland 1. Follicles are _____________________________________________________ 2. Colloid is _______________________________________________________ 3. Thyroglobulin is __________________________________________________ 4. Extrafollicular cells are located ______________________________________ 5. The follicular cells produce _________________________________________ C. Thyroid Hormones 1. The three hormones produced by the thyroid gland are ___________________ __________________________________________________________________ 2. The actions of thyroxine and triiodothyronine are ________________________ __________________________________________________________________ 3. The secretion of T3 and T4 are controlled by ____________________________ __________________________________________________________________ 4. Follicular cells require ___________________________ to produce T3 and T4. 5. The actions of calcitonin are ________________________________________ __________________________________________________________________ 6. The secretion of calcitonin is controlled by _____________________________ __________________________________________________________________ VII. Parathyroid Glands A. Introduction 1. Parathyroid glands are located _______________________________________ 2. Usually a person has ______________________________ parathyroid glands. B. Structure of the Glands 1. Each parathyroid gland is covered by _________________________________ 2. The body of a parathyroid gland consists of ____________________________ __________________________________________________________________ C. Parathyroid Hormone 1. The actions of PTH are ____________________________________________ __________________________________________________________________ 2. The secretion of PTH is controlled by _________________________________ __________________________________________________________________ VIII. Adrenal Glands A. Structure of the Glands 1. The adrenal glands are shaped like ___________________________________ 2. The two parts of an adrenal gland are _________________________________ 3. The adrenal medulla consists of______________________________________ __________________________________________________________________ 4. The adrenal cortex is composed of ___________________________________ 5. The three layers of the adrenal cortex are ______________________________ __________________________________________________________________ B. Hormones of the Adrenal Medulla 1. The two hormones released by the adrenal medulla are ___________________ __________________________________________________________________ 2. The actions of epinephrine and norepinephrine are _______________________ __________________________________________________________________ 3. The secretion of epinephrine and norepinephrine are controlled by __________ __________________________________________________________________ C. Hormones of the Adrenal Cortex 1. Introduction a. The adrenal cortex produces more than ___________ different steroids. b. The most important adrenal cortical hormones are _________________ ____________________________________________________________ 2. Aldosterone a. Aldosterone is secreted by _______________________________ and is called a mineralocorticoid because ________________________________ ____________________________________________________________ b. The actions of aldosterone are _________________________________ ____________________________________________________________ c. The secretion of aldosterone is controlled by _____________________ ____________________________________________________________ 3. Cortisol a. Cortisol is secreted by __________________________________ and is called a glucocorticoid because __________________________________ ____________________________________________________________ b. The actions of cortisol are ____________________________________ ____________________________________________________________ c. The secretion of cortisol is controlled by _________________________ ____________________________________________________________ 4. Sex Hormones a. The sex hormones are secreted by ______________________________ ____________________________________________________________ b. The actions of the sex hormones are ____________________________ ____________________________________________________________ c. Examples of sex hormones are _________________________________ ____________________________________________________________ IX. Pancreas A. Structure of the Gland 1. The pancreas is located ____________________________________________ 2. The endocrine portion of the pancreas consists of ________________________ __________________________________________________________________ 3. Three cell types of the pancreatic islets are _____________________________ 4. Alpha cells secrete ________________________________________________ 5. Beta cells secrete _________________________________________________ 6. Delta cells secrete ________________________________________________ B. Hormones of the Pancreatic Islets 1. The actions of glucagon are _________________________________________ __________________________________________________________________ 2. The secretion of glucagon is controlled by _____________________________ __________________________________________________________________ 3. The actions of insulin are ___________________________________________ __________________________________________________________________ 4. The secretion of insulin is controlled by _______________________________ __________________________________________________________________ 5. The function of somatostatin is ______________________________________ X. Other Endocrine Glands A. Pineal Gland 1. The pineal gland is located _________________________________________ 2. The pineal gland produces the hormone _______________________________ 3. The functions of melatonin are ______________________________________ B. Thymus gland 1. The thymus gland is located ________________________________________ 2. The thymus gland secretes a group of hormones called ___________________ 3. The function of thymosin is _________________________________________ __________________________________________________________________ C. Reproductive Organs 1. Reproductive organs that secrete hormones are__________________________ __________________________________________________________________ 2. Examples of hormones produced by reproductive organs are _______________ __________________________________________________________________ D. Other Hormone-Producing Organs 1. The hormone produced by the heart is _________________________________ 2. The hormone produced by the kidneys is ______________________________ XI. Stress and Its Effects A. Introduction 1. A stressor is _____________________________________________________ 2. Stress is ________________________________________________________ B. Types of Stress 1. Examples of physical stress include __________________________________ __________________________________________________________________ 2. Examples of psychological stress are _________________________________ __________________________________________________________________ C. Responses to Stress 1. The general stress syndrome is ______________________________________ __________________________________________________________________ 2. Major events of the general stress syndrome are _________________________ __________________________________________________________________ XII. Life-Span Changes A. General changes in the glands of the endocrine system are ______________________ ________________________________________________________________________ B. Treatments for endocrine disorders include __________________________________ ________________________________________________________________________ C. Levels of _________________________ increase with age and as a result, the kidneys ________________________________________________________________________ D. The decrease of calcitonin levels with age increases the risk of ___________________ E. The most obvious changes in endocrine function involve _______________________ ________________________________________________________________________