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Endocrine System Hormones 2007-2008 Animals rely on 2 systems for regulation (Watch Mr.A – (#1) Cell Communication Video) endocrine system system of ductless glands secrete chemical signals directly into blood chemical travels to target tissue target cells have receptor proteins slow, long-lasting response nervous system system of neurons transmits “electrical” signal & release neurotransmitters to target tissue fast, short-lasting response Regulation Why are hormones needed? chemical messages from one body part to another communication needed to coordinate whole body daily homeostasis & regulation of large scale changes solute levels in blood glucose, Ca++, salts, etc. metabolism growth development maturation reproduction growth hormones Regulation by chemical messengers Neurotransmitters released by neurons Hormones release by endocrine glands endocrine gland neurotransmitter axon hormone carried by blood receptor proteins receptor proteins target cell Lock & Key system Classes of Hormones Protein-based hormones polypeptides small proteins: insulin, ADH insulin glycoproteins large proteins + carbohydrate: FSH, LH amines modified amino acids: epinephrine, melatonin Lipid-based hormones steroids modified cholesterol: sex hormones, aldosterone How do hormones act on target cells Lipid-based hormones hydrophobic & lipid-soluble diffuse across cell membrane & enter cells bind to receptor proteins in cytoplasm & nucleus bind to DNA as transcription factors turn on genes Protein-based hormones hydrophilic & not lipid soluble can’t diffuse across cell membrane bind to receptor proteins in cell membrane trigger secondary messenger pathway activate internal cellular response enzyme action, uptake or secretion of molecules… Action of lipid (steroid) hormones steroid hormone target cell S S cytoplasm 1 blood S protein carrier cross cell membrane 2 binds to receptor protein becomes transcription factor 5 S 3 mRNA read by ribosome plasma membrane 4 DNA mRNA nucleus 6 protein 7 protein secreted ex: secreted protein = growth factor (hair, bone, muscle, gametes) See Mr. A’s signal-transduction pathway (#2) Video NOW Action of protein hormones 1 protein hormone P signal plasma membrane binds to receptor protein activates G-protein activates enzyme cAM P receptor protein activates cytoplasmic signal GTP cytoplasm target cell acts as 2° messenger transduction ATP ATP activates enzyme 2 secondary messenger system activates enzyme produces an action 3 response Ex: Action of epinephrine (adrenaline) on liver cells adrenal gland signal 1 epinephrine activates G protein receptor protein in cell membrane activates GTP 3 activates adenylyl cyclase cAMP GDP transduction 4 GTP 2 ATP activates protein kinase-A 5 activates phosphorylase kinase cytoplasm liver cell released to blood activates glycogen phosphorylase glycogen 6 glucose 7 response Benefits of a 2° messenger system1 signal Activated adenylyl cyclase receptor protein 2 Not yet activated amplification 4 3 GTP amplification cAMP amplification 5 G protein protein kinase 6 amplification Amplification! enzyme Cascade multiplier! FAST response! 7 amplification product Maintaining homeostasis hormone 1 lowers body condition gland high specific body condition low raises body condition gland hormone 2 Negative Feedback Model Nervous System Control Feedback Controlling Body Temperature nerve signals hypothalamus dilates surface blood vessels sweat high body temperature (37°C) low hypothalamus constricts surface shiver blood vessels nerve signals Endocrine System Control Regulation of Blood Sugar Feedback insulin liver stores glycogen body cells take up sugar from blood pancreas liver high blood sugar level (90mg/100ml) low triggers hunger liver releases glucose liver pancreas glucagon reduces appetite What is the effect of changes in the signal transduction pathways? Watch this Video (#3)to find out! Nervous & Endocrine systems linked Hypothalamus = “master nerve control center” nervous system receives information from nerves around body about internal conditions releasing hormones: regulates release of hormones from pituitary Pituitary gland = “master gland” endocrine system secretes broad range of “tropic” hormones regulating other glands in body hypothalamus posterior pituitary anterior tropic hormones = target endocrine glands hypothalamus thyroid-stimulating hormone (TSH) Thyroid gland Adrenal cortex posterior antidiuretic pituitary hormone (ADH) anterior pituitary gonadotropic hormones: folliclestimulating hormone (FSH) & luteinizing hormone (LH) Kidney tubules Muscles of uterus Melanocyte in amphibian Bone and muscle Testes Ovaries Mammary glands in mammals Why is there Homology in hormones? Watch Mr. A’s Video – (#4) Evolutionary Significance of Cell-Cell communication What does this tell you about these hormones? How could these hormones have different effects? same gene family gene duplication? prolactin mammals milk production birds fat metabolism fish amphibians salt & water balance metamorphosis & maturation growth hormone growth & development Regulating metabolism Hypothalamus TRH = TSH-releasing hormone Anterior Pituitary TSH = thyroid stimulating hormone Thyroid produces thyroxine hormones metabolism & development bone growth mental development metabolic use of energy blood pressure & heart rate muscle tone digestion reproduction tyrosine + iodine thyroxines Goiter Iodine deficiency causes thyroid to enlarge as it tries to produce thyroxine + tyrosine + iodine ✗ ✗ thyroxines Endocrine System Control Feedback Regulation of Blood Calcium calcitonin kidney reabsorption of Ca++ thyroid Ca++ deposited in bones high blood calcium level Ca++ uptake in intestines (10 mg/100mL) low activated Vitamin D bones release Ca++ kidney reabsorption of Ca++ parathyroid parathyroid hormone (PTH) Feedback Female reproductive cycle egg matures & is released (ovulation) estrogen builds up uterus lining corpus luteum ovary progesterone FSH & LH maintains uterus lining pituitary gland fertilized egg (zygote) hCG yes pregnancy GnRH hypothalamus no corpus luteum breaks down progesterone drops menstruation corpus luteum progesterone maintains uterus lining Any Questions?? Robert Wadlow 1918-1940 8' 11" 2009-2010