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Endocrine System Hormones 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 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 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 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 membrane & enter cells • bind to receptor proteins in cytoplasm & nucleus • bind to DNA as transcription factors • Protein-based hormones – hydrophilic & not lipid soluble • • • • can’t diffuse across membrane 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 S 1 2 blood protein carrier receptor protein 4 transcription factor S 3 DNA nucleus mRNA 5 protein plasma membrane ex: growth factors (hair, bone, muscle, gametes) 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 target 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 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 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! FAST response! amplification enzyme 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 brain sweat high body temperature low brain constricts surface shiver blood vessels nerve signals dilates surface blood vessels 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 liver releases sugar liver pancreas glucagon reduces appetite Blood Osmolarity Feedback ADH pituitary increased water reabsorption increase thirst nephron high blood osmolarity blood pressure nephron adrenal gland low increased water & salt reabsorption JuxtaGlomerular Apparatus nephron (JGA) renin aldosterone Stimulates production angiotensin 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 posterior 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 Testis Ovary Mammary glands in mammals Homology in hormones 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 thyroxine Goiter Iodine deficiency causes thyroid to enlarge as it tries to produce thyroxine Regulation of Blood Calcium Feedback calcitonin kidney filters Ca++ Ca++ deposited in bones high blood calcium level uptake in intestines Ca++ (10 mg/100mL) low activated Vitamin D bones release Ca++ kidney reabsorbs Ca++ parathyroid Parathyroid hormone Feedback Female reproductive cycle egg matures & is released (ovulation) estrogen builds up uterus lining corpus luteum ovary Progestins fertilized egg FSH & LH maintains uterus lining HCG yes pregnancy GnRH hypothalamus no corpus luteum breaks down progesterone drops menstruation progesterone maintains uterus lining Any Questions?? Robert Wadlow 1918-1940 8' 11"
