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Endocrine System Hormones AP Biology 2007-2008 Regulation Why are hormones needed? chemical messages from one body part to another communication needed to coordinate whole body homeostasis & regulation metabolism growth development maturation reproduction AP Biology growth hormones Regulation & Communication Animals rely on 2 systems for regulation endocrine system system of ductless glands secrete chemical signals directly into blood chemical travels to target tissue slow, long-lasting response nervous system system of neurons transmits “electrical” signal & release neurotransmitters to target tissue fast, short-lasting response AP Biology Regulation by chemical messengers Neurotransmitters released by neurons Hormones release by endocrine glands endocrine gland neurotransmitter axon hormone carried by blood receptor proteins AP Biology receptor proteins target cell 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 AP Biology How do hormones act on target cells Lipid-based hormones lipid-soluble diffuse across membrane & enter cells bind to receptor proteins in cytoplasm & then this hormone-receptor complex moves into nucleus bind to receptor proteins in nucleus AP Biology bind to DNA as transcription factors 2004- Action of lipid (steroid) hormones steroid hormone target cell S S cytoplasm S 1 2 blood protein carrier receptor protein 4 transcription factor S 3 DNA nucleus AP Biology mRNA 5 protein plasma membrane ex: growth factors (hair, bone, muscle, gametes) How do hormones act on target cells Protein-based hormones hydrophilic & not lipid soluble Signal molecule Cell surface receptor enzyme can’t diffuse across cAMP membrane trigger secondary (2°) messenger pathway G protein ATP transmit “signal” across membrane “signal transduction” usually activates a series of 2° messengers multi-step “cascade” Nucleus activate cellular response enzyme action, uptake or AP Biology Target protein secretion of molecules, etc. Cytoplasm 2004- Action of protein hormones signal-transduction pathway 1 protein hormone P signal plasma membrane activates ion channel or enzyme 2° messenger receptor protein transduction ATP activates enzyme cytoplasm AP target Biology cell 2 secondary messenger system activates enzyme produces an action 3 response Signal Transduction pathway 1 protein hormone P activates enzyme G protein cAMP receptor protein 2 GTP cytoplasm AP Biology 3 ATP activates enzyme activates enzyme produces an action secondary messenger system 4 5 Action of epinephrine (adrenalin) 1 epinephrine activates adenylyl cyclase adrenal gland G protein cAMP receptor protein 2 GTP cytoplasm AP Biology liver cell 3 ATP activates protein kinase-A activates phosphorylase glycogen 5 4 glucose released to blood Benefits of a 2° messenger system signal 1 Activated adenylyl cyclase receptor protein 2 Not yet activated amplification 4 3 GTP amplification cAMP amplification 5 G protein protein kinase 6 amplification enzyme Amplification! 7 FAST response! AP Biology amplification product Hormones & Homeostasis Negative feedback Inhibition Hypothalamus stimulus triggers control mechanism that inhibits further change body temperature sugar metabolism Positive feedback stimulus triggers control mechanism that amplifies effect lactation AP Biology labor contractions – Releasing hormones (TRH, CRH, GnRH) Inhibition Anterior pituitary Tropic hormones (TSH, ACTH, FSH, LH) Target glands (thyroid, adrenal cortex, gonads) Hormones 2004- – Maintaining homeostasis hormone 1 lowers body condition gland high specific body condition low raises body condition AP Biology gland hormone 2 Negative Feedback Model Nervous System Control Feedback Controlling Body Temperature nerve signals brain sweat high body temperature low brain constricts surface shiver blood vessels AP Biology nerve signals dilates surface blood vessels Endocrine System Control Regulation of Blood Sugar Feedback insulin liver stores sugar body cells take up sugar from blood pancreas high liver blood sugar level low triggers hunger AP Biology liver releases sugar liver pancreas reduces appetite Regulating blood sugar levels beta islet cells pancreas - triggers release of glucose by liver - stimulates appetite AP Biology - triggers uptake of glucose by body cells - triggers storage in liver - depresses appetite pancreas 2004alpha islet cells Nervous & Endocrine systems linked Hypothalamus = “master control center” nervous system receives information from nerves around body about internal conditions regulates release of hormones from pituitary Pituitary gland = “master gland” endocrine system secretes broad range of hormones regulating other glands hypothalamus anterior pituitary AP Biology posterior Regulating metabolism Hypothalamus TRH = TSH-releasing hormone Anterior Pituitary TSH = thyroid stimulating hormone Thyroid produces thyroxine hormones metabolism & development AP Biology bone growth mental development metabolic use of energy blood pressure & heart rate muscle tone digestion reproduction tyrosine + iodine thyroxine Hypothalamus thyroid-stimulating hormone (TSH) Thyroid gland antidiuretic posterior hormone pituitary (ADH) anterior pituitary Kidney tubules Muscles of uterus Adrenal cortex gonadotropic hormones: folliclestimulating hormone (FSH) & luteinizing hormone (LH) Melanocyte in amphibian Bone and muscle AP Biology Testis Ovary Mammary glands in mammals Goiter Iodine deficiency causes thyroid to enlarge as it tries to produce thyroxine AP Biology Any Questions?? Robert Wadlow 1918-1940 8' 11" AP Biology 2007-2008