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Chapter 45 Hormones and the Endocrine System A hormone called ecdysteroid regulates the timing of metamorphosis in this anise swallowtail butterfly. You must know: • Two ways hormones affect target organs. • The secretion, target, action, and regulation of at least 3 hormones. • An illustration of both positive and negative feedback in the regulation of homeostasis by hormones. Types of Intercellular Signaling • Endocrine System = Hormone-secreting cells + Tissues • Endocrine glands: ductless, secrete hormones directly into body fluids • Hormones: chemical signals that cause a response in target cells (receptor proteins for specific hormones) – Affects 1 tissue, a few, or most tissues in body – Or affect other endocrine glands (tropic hormones) • Regulation by Positive & Negative Feedback Pheromones Hormones Local Regulators Chemical signal from 1 individual to another individual Chemical signal from endocrine gland through blood to target cell Chemical signal from one cell to an adjacent cell Eg. cytokines, Eg. ant trail; sex Eg. peptide, growth factors, phermones steroid hormones nitric oxide (NO) Types of Hormones Peptide Steroid • Water-soluble • Bind to receptors on plasma membrane & triggers signal transduction pathway • Affects protein activity already present in cell • Rapid response • Short-lived • Eg. oxytocin, insulin, epinephrine • Lipid-soluble • Enters cell & binds to intracellular receptors • Causes change in gene expression (protein synthesis) • Slower response • Longer life • Eg. androgens (testosterone), estrogen, progesterone, cortisol Epinephrine: one hormone many effects 1.Liver cells break 2.Blood vessels to down glycogen and skeletal muscles release glucose dilate 3.Blood vessels to intestines constrict Master Glands Hypothalamus Pituitary Gland Master Glands Hypothalamus • Receives info from nerves and brain • Initiates endocrine signals Posterior pituitary gland: • Oxytocin: contract uterine muscles, eject milk in nursing Pituitary Gland • Antidiuretic Hormone (ADH): promote H2O retention by kidneys Anterior pituitary gland: • Follicle-stimulating hormone (FSH): development of ovarian follicles (eggs); promote sperm production • Luteinizing hormone (LH): trigger ovulation; stimulate testosterone production in testes Hypothalamus regulation of Posterior Pituitary gland Hypothalamus regulation of Anterior Pituitary gland Negative feedback systems: • Thyroid hormones • Blood Ca2+ levels • Blood glucose levels Positive feedback system: • Oxytocin (birthing process; release of milk/suckling) BIOFLIX: HOMEOSTASIS – BLOOD SUGAR Control of Blood Glucose High blood glucose Liver breaks down glycogen and releases glucose into blood Insulin released from pancreas Body cells take up glucose Liver stores glucose as glycogen Glucagon released from pancreas Blood glucose drops Diabetes Mellitus • Type I diabetes (10%):deficiency of insulin – Insulin-dependent – Autoimmune disorder beta cells of pancreas destroyed • Type II diabetes (90%): failure of target cells to respond to insulin – Non-insulin dependent – Insulin produced cells don’t respond (defect in insulin receptor or response pathway) – Risk factors: obesity, lack of exercise Anabolic-Androgenic Steroid (AAS) Use • Legally prescribed to treat hormone deficiency, loss of muscle mass (cancer, AIDS) • Used to enhance performance and improve physical appearance Effects of AAS Abuse Source: www.drugabuse.gov/infofacts/steroids.html • • • • • • • aggression extreme mood swings liver damage jaundice fluid retention high blood pressure increases in LDL (“bad” cholesterol) • decreases in HDL (“good” cholesterol) • renal failure • severe acne • For men—shrinking of the testicles, reduced sperm count, infertility, baldness, development of breasts, increased risk for prostate cancer • For women—growth of facial hair, malepattern baldness, changes in or cessation of the menstrual cycle, enlargement of the clitoris, deepened voice • For adolescents—stunted growth due to premature skeletal maturation and accelerated puberty changes; risk of not reaching expected height if AAS is taken before the typical adolescent growth spurt • In addition, people who inject AAS run the added risk of contracting or transmitting HIV/AIDS or hepatitis.