Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Chapter 11 Endocrine Glands: Secretion and Action of Hormones Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 11-1 Endocrine Glands Are ductless and secrete hormones into bloodstream Hormones go to target cells that contain receptor proteins for it Neurohormones are secreted into blood by specialized neurons Hormones affect metabolism of targets Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 11-4 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 11-5 Chemical Classification of Hormones Amine hormones are derived from tyrosine or tryptophan Include NE, Epi, thyroxine, melatonin Polypeptide/protein hormones are chains of amino acids Include ADH, GH, insulin, oxytocin, glucagon, ACTH, PTH Glycoproteins include LH, FSH, TSH Steroids are lipids derived from cholesterol Include testosterone, estrogen, progesterone and cortisol Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 11-7 Hormone Interactions A tissue usually responds to # of hormones 2 hormones are synergistic if work together to produce an effect Produce a larger effect together than individual effects added together A hormone has permissive effect if it enhances responsiveness of a target organ to 2nd hormone If action of 1 hormone inhibits effect of another, it is antagonistic Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 11-13 Hormone Levels and Tissue Responses Half-life is time required for blood level to be reduced by half Ranges from mins to hrs for most (days for thyroid hormones) Normal tissue responses are produced only when hormones are in physiological range High (pharmacological) doses can cause # of side effects Probably by binding to receptors of other hormones Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 11-14 Anterior Pituitary Secretes 6 trophic hormones that maintain size of targets High blood levels cause target to hypertrophy Low levels cause atrophy Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 11-39 Anterior Pituitary continued Growth hormone (GH) promotes growth, protein synthesis, and movement of amino acids into cells Thyroid stimulating hormone (TSH) stimulates thyroid to produce and secrete T4 and T3 Adrenocorticotrophic hormone (ACTH) stimulates adrenal cortex to secrete cortisol, aldosterone Follicle stimulating hormone (FSH) stimulates growth of ovarian follicles and sperm production Luteinizing hormone (LH) causes ovulation and secretion of testosterone in testes Prolactin (PRL) stimulates milk production by mammary glands Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 11-40 Anterior Pituitary continued Releasing and inhibiting hormones from hypothalamus are released from axon endings into capillary bed in median eminence Carried by hypothalamohypophyseal portal system directly to another capillary bed in A. Pit. Diffuse into A. Pit. and regulate secretion of its hormones Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 11-42 Feedback Control of Anterior Pituitary Involves short feedback loop in which retrograde flow of blood and hormones from A. Pit. to hypothalamus inhibits secretion of releasing hormone Involves negative feedback of target gland hormones And during menstrual cycle, estrogen stimulates “LH surge” by positive feedback Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 11-43 Higher Brain Function and Anterior Pituitary Secretion Hypothalamus receives input from higher brain centers that can affect A. Pit. secretion E.g. emotional states and psychological stress can affect circadian rhythms, menstrual cycle, and adrenal hormones Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 11-44 Posterior Pituitary Stores and releases 2 hormones produced in hypothalamus: Antidiuretic hormone (ADH/vasopressin) which promotes H2O conservation by kidneys Oxytocin which stimulates contractions of uterus during parturition And contractions of mammary gland alveoli for milkejection reflex Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 11-45 Adrenal Glands Medulla synthesizes and secretes 80% Epi and 20% NE Controlled by sympathetic Cortex is controlled by ACTH and secretes: Cortisol which inhibits glucose utilization and stimulates gluconeogenesis Aldosterone which stimulate kidneys to reabsorb Na+ and secrete K+ And some supplementary sex steroids Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 11-49 Adrenal Cortex Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 11-50 Adrenal Medulla Hormonal effects of Epi last 10X longer than NE Innervated by preganglionic Symp fibers Activated during "fight or flight" response Causes: Increased respiratory rate Increased HR and cardiac output General vasoconstriction which increases venous return Glycogenolysis and lipolysis Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 11-51 Stress and the Adrenal Gland Stress induces a nonspecific response called general adaptation syndrome (GAS) Causes ACTH and cortisol release Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 11-52 Stress and the Adrenal Gland Chronic stress can induce high levels of cortisol that cause a number of negative effects: atrophy of hippocampus (involved in memory) reduced sensitivity of tissues to insulin (insulin resistance) inhibition of vagus nerve activity suppression of growth hormone, thyroid hormone, and gonadotropins Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 11-53 Thyroid Gland Is located just below the larynx Secretes T4 and T3 which set BMR and are needed for growth, development Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 11-55 Diseases of the Thyroid - Goiter In absence of sufficient dietary iodide, T4 and T3 cannot be made and levels are low Low T4 and T3 don’t provide negative feedback and TSH levels go up Because TSH is a trophic hormone, thyroid gland grows Resulting in a goiter Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 11-58 Diseases of the Thyroid - Hypothyroidism People with inadequate T4 and T3 levels are hypothyroid Have low BMR, weight gain, lethargy, cold intolerance And myxedema = puffy face, hands, feet During fetal development hypothyroidism can cause cretinism (severe mental retardation) Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 11-59 Diseases of the Thyroid - Hyperthyroidism Goiters are also produced by Grave's disease Autoimmune disease where antibodies act like TSH and stimulate thyroid gland to grow and oversecrete = hyperthyroidism Characterized by exopthalmos, weight loss, heat intolerance, irritability, high BMR Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 11-60 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 11-61 Parathyroid Glands Are 4 glands embedded in lateral lobes of thyroid gland Secrete Parathyroid hormone (PTH) Most important hormone for control of blood Ca2+ levels Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 11-62 Parathyroid Hormone Release stimulated by decreased blood Ca2+ Acts on bones, kidney, and intestines to increase blood Ca2+ levels Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 11-63 Islets of Langerhans 11-64 Islets of Langerhans continued Alphas secrete glucagon in response to low blood glucose Stimulates glycogenolysis and lipolysis Increases blood glucose Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 11-66 Islets of Langerhans continued Betas secrete insulin in response to low blood glucose Promotes entry of glucose into cells And conversion of glucose into glycogen and fat Decreases blood glucose Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 11-67 Pineal Gland continued SCN is primary timing center for circadian rhythms Reset by daily light/dark changes Melatonin is involved in aligning physiology with sleep/wake cycle and seasons Secreted at night and is inhibited by light Inhibits GnRH (antigonadotropic) in many animals Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 11-70 Thymus Is located around trachea below thyroid Produces T cells of immune system and hormones that stimulate them Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 11-71 Sex and Reproductive Hormones Gonads (testes and ovaries) secrete steroid hormones testosterone, estrogen, and progesterone Placenta secretes estrogen, progesterone, hCG, and somatomammotropin Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 11-72 Prostaglandins (PGs) Are produced in almost every organ Belong to eicosanoid family -- all derived from arachidonic acid of plasma membrane Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 11-75 Prostaglandins (PGs) continued Have wide variety of functions Different PGs may exert antagonistic effects in tissues Some promote smooth muscle contraction and some relaxation Some promote clotting; some inhibit Promotes inflammatory process of immune system Plays role in ovulation Inhibits gastric secretion in digestive system Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 11-76 Prostaglandins (PGs) continued Cyclooxygenase (COX) 1 and 2 are involved in PG synthesis (Fig 11.34) Are targets of a number of inhibitory non-steroidal antiinflammatory drugs (NSAIDs) Aspirin, indomethacin, ibuprofen inhibit both COX 1 and 2 thereby producing side effects Celebrex and Vioxx only inhibit COX 2 and thus have few side effects Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 11-77