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Chapter 45.

Chapter 45. 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.

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Chapter 45.

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  1. Chapter 45. Endocrine System Hormones

  2. 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

  3. Regulation & Communication • Animals rely on 2 systems for regulation • endocrine system • ductless gland which secrete chemical signals directly into blood • chemical travels to target tissue • slow, long-lasting response • nervous system • system of neurons, central nerve system • transmits “electrical” signal to target tissue • fast, short-lasting response

  4. Regulation by chemical messengers • Neurotransmitters released by neurons • Hormones release by endocrine glands Endocrine gland Axon Neurotransmitter Hormone carried by blood Receptor proteins Target cell

  5. Classes of Hormones • Protein-based hormones • polypeptides • small proteins: insulin, ADH • glycoproteins • large proteins + carbohydrate: FSH, LH • amines • modified amino acids: epinephrine, melatonin • Lipid-based hormones • steroids • modified cholesterol: sex hormones, aldosterone

  6. 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 • bind to DNA as transcription factors

  7. Action of steroid (lipid) hormones Cytoplasm Blood plasma Steroid hormone S S 1 Protein carrier S Plasma membrane 2 1 Steroid hormone (S) passes through plasma membrane. 2 Inside target cell, the steroid hormone binds to a specific receptor protein in the cytoplasm or nucleus. 4 S 3 Hormone-receptor complex enters nucleus & binds to DNA, causing gene transcription 3 DNA mRNA 5 Protein 4 Protein synthesis is induced. Nucleus 5 Protein is produced.

  8. How do hormones act on target cells • Protein-based hormones • hydrophilic & not lipid soluble • can’t diffuse across membrane • trigger secondary (2°) messenger pathway • transmit “signal” across membrane • “signal transduction” • usually activates a series of 2° messengers • multi-step “cascade” • activate cellular response • enzyme action, uptake or secretion of molecules, etc. Signal molecule Cell surface receptor enzyme cAMP G protein ATP Targetprotein Nucleus Cytoplasm

  9. Action of protein hormones 1 Protein hormone activatesenzyme G protein cAMP Receptor protein 3 2 ATP protein messengercascade activates enzyme GTP activates enzyme 4 Cytoplasm Produces an action

  10. Action of epinephrine (adrenalin) Liver cell 1 Epinephrine activatesadenylyl cyclase adrenal gland G protein Receptor protein cAMP 3 2 ATP activates protein kinase-A GTP releasedto blood activates phosphorylase 4 Cytoplasm Glycogen Glucose

  11. Benefits of a 2° messenger system Amplification! 1 Receptor protein Activated adenylyl cyclase Signal molecule Not yet activated Amplification 2 4 Amplification cAMP 3 5 GTP G protein Protein kinase 6 Amplification Enzyme Amplification 7 Enzymatic product

  12. Endocrine system • Ductless glands release hormones into blood Duct glands = exocrine (tears, salivary)

  13. Major vertebrate hormones (1)

  14. Major vertebrate hormones (2)

  15. Endocrine & Nervous system links • 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 rangeof hormones regulating other glands

  16. Hypothalamus Thyroid-stimulating Hormone (TSH) Antidiuretic hormone (ADH) Posterior pituitary Thyroid gland Anterior pituitary Kidney tubules Adrenocorticotropic hormone (ACTH) Oxytocin Muscles of uterus Melanocyte-stimulating hormone (MSH) Gonadotropic hormones: Follicle- stimulating hormone (FSH) & luteinizing hormone (LH) Growth hormone (GH) Prolactin (PRL) Adrenal cortex Melanocyte in amphibian Mammary glands in mammals Bone and muscle Ovary Testis

  17. Homology in hormones What does this tell you about these hormones? same gene family prolactin growthhormone mammals birds fish amphibians milkproduction fatmetabolism salt &waterbalance metamorphosis& maturation growth& development

  18. Hormones & Homeostasis • Negative feedback • stimulus triggers control mechanism that inhibits further change • body temperature • sugar metabolism • Positive feedback • stimulus triggers control mechanism that amplifies effect • lactation • labor contractions Inhibition Hypothalamus – Releasing hormones (TRH, CRH, GnRH) Inhibition Anterior pituitary – Tropic hormones (TSH, ACTH, FSH, LH) Target glands (thyroid, adrenal cortex, gonads) Hormones

  19. Regulating blood sugar levels beta islet cells • triggers uptake of glucose by body cells • triggers storage in liver • - depresses appetite pancreas - triggers release of glucose by liver - stimulates appetite pancreas alpha islet cells

  20. Regulating blood osmolarity If amount of dissolved material in blood too high, need to dilute blood Dehydration Lowers blood volume & pressure Osmotic concentration of blood increases Negative feedback Osmoreceptors Negative feedback ADH synthesized in hypothalamus ADH ADH released from posterior pituitary into blood Increased water retention Increased vasoconstriction leading to higher blood pressure Reduced urine volume

  21. 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

  22. Goiter Iodine deficiency causes thyroid to enlarge as it tries to produce thyroxine

  23. Homology in hormones Thyroxine stimulates metamorphosis in amphibians TRH TSH Thyroxine Thyroxine secretion rate TRH rises –35 –30 –25 –20 –15 –10 –5 0 +5 +10 Days from emergence of forelimb

  24. Regulating blood calcium levels Thyroid Parathyroids Low blood Ca++ – Parathyroid hormone (PTH) Negative feedback Increased absorption of Ca++ from intestine due to PTH activation of Vitamin D Reabsorption of Ca++ & excretion of PO4 Osteoclasts dissolve CaPO4 crystals in bone, releasing Ca++ Increased blood Ca++

  25. Hormonal regulation of insect development Neurosecretory cells Brain hormone Juvenile hormone Prothoracic gland Low amounts Molting hormone Adult molt Larval molt Pupal molt

  26. Any Questions??

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