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Chapter 45 ~ Chemical Signals in Animals Endocrine system ~ Hormones

Chapter 45 ~ Chemical Signals in Animals Endocrine system ~ Hormones. growth hormones. Regulatory systems. Hormone ~ chemical signal secreted into body fluids (blood) communicating regulatory messages Target cells ~ body cells that respond to hormones

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Chapter 45 ~ Chemical Signals in Animals Endocrine system ~ Hormones

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  1. Chapter 45 ~ Chemical Signals in AnimalsEndocrine system ~Hormones growth hormones

  2. Regulatory systems • Hormone~ chemical signal secreted into body fluids (blood) communicating regulatory messages • Target cells~ body cells that respond to hormones • Endocrine system/glands~ hormone secreting system/glands (ductless); exocrine glands secrete chemicals (sweat, mucus, enzymes) through ducts • Neurosecretory cells~ actual cells that secrete hormones • Feedback mechanisms~ negative and positive

  3. Local regulators: cells adjacent to or near point of secretion • Growth factors ~ proteins for cell proliferation • Nitric oxide (NO) ~ neurotransmitter; cell destruction; vessel dilation • Prostaglandins ~ modified fatty acids secreted by placenta and immune system; also found in semen

  4. 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

  5. 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 • 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

  6. 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 Lock & Keysystem target cell

  7. 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 insulin

  8. Mode of Action: Chemical Signaling • 1- Plasma membrane reception • signal-transduction pathways (neurotransmitters, growth factors, most hormones) • 2- Cell nucleus reception • steroid hormones, thyroid hormones, some local regulators

  9. Action of lipid (steroid) hormones steroid hormone target cell blood S 1 S cross cell membrane protein carrier S 2 cytoplasm binds to receptor protein becomes transcription factor 5 mRNA read by ribosome S 3 plasma membrane 4 DNA mRNA 6 7 nucleus protein protein secreted ex: secreted protein = growth factor (hair, bone, muscle, gametes)

  10. Action of protein hormones signal-transduction pathway 1 signal proteinhormone plasma membrane P activates G-protein binds to receptor protein activates enzyme cAMP acts as 2° messenger receptorprotein ATP transduction GTP activatescytoplasmicsignal ATP activates enzyme 2 secondary messengersystem activates enzyme cytoplasm response 3 produces an action target cell

  11. Benefits of a 2° messenger system Amplification! 1 signal Activated adenylyl cyclase receptor protein Not yet activated 2 amplification 4 amplification 3 cAMP 5 amplification GTP G protein protein kinase 6 amplification enzyme Cascade multiplier! 7 amplification FAST response! product

  12. high low Maintaining homeostasis hormone 1 lowersbody condition gland specific body condition raisesbody condition gland Negative FeedbackModel hormone 2

  13. Vertebrate Endocrine System • Tropic hormones ~ a hormone that has another endocrine gland as a target • Hypothalamus~pituitary • Pituitary gland • Pineal gland • Thyroid gland • Parathyroid glands • Thymus • Adrenal glands • Pancreas • Gonads (ovary, testis)

  14. 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 rangeof “tropic” hormones regulating other glands in body hypothalamus posterior pituitary anterior

  15. tropic hormones = target endocrine glands hypothalamus thyroid-stimulating hormone (TSH) antidiuretic hormone (ADH) posterior pituitary Thyroid gland anterior pituitary Kidney tubules adrenocorticotropic hormone (ACTH) oxytocin Muscles of uterus gonadotropic hormones: follicle- stimulating hormone (FSH) & luteinizing hormone (LH) melanocyte-stimulating hormone (MSH) growth hormone (GH) prolactin (PRL) Adrenal cortex Melanocyte in amphibian Mammary glands in mammals Bone and muscle Ovaries Testes

  16. The hypothalamus & pituitary, I • Releasing and inhibiting hormones • Anterior pituitary: • Growth (GH)~bones √gigantism/dwarfism √acromegaly • Prolactin (PRL)~mammary glands; milk production • Follicle-stimulating (FSH) & • Luteinizing (LH)~ovaries/testes • Thyroid-stimulating (TSH)~ thyroid • Adrenocorticotropic (ACTH)~ adrenal cortex • Melanocyte-stimulating (MSH) • Endorphins~natural ‘opiates’; brain pain receptors

  17. The pituitary, II • The posterior pituitary: • Oxytocin~ uterine and mammary gland cell contraction • Antidiuretic (ADH)~ retention of water by kidneys

  18. The pineal, thyroid, & parathyroid • Melatonin~ pineal gland; biological rhythms • Thyroid hormones: Calcitonin~ lowers blood calcium Thyroxine~ metabolic processes • Parathyroid (PTH)~raises blood calcium

  19.  kidney reabsorption of Ca++ thyroid Ca++ depositedin bones high  Ca++uptakein intestines low parathyroid  kidney reabsorption of Ca++ bones release Ca++ Endocrine System Control Regulation of Blood Calcium Feedback calcitonin blood calcium level(10 mg/100mL) activated Vitamin D parathyroid hormone (PTH)

  20. 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

  21. The pancreas • Islets of Langerhans • Alpha cells: •glucagon~ raises blood glucose levels • Beta cells: •insulin~ lowers blood glucose levels • Type I diabetes mellitus (insulin-dependent; autoimmune disorder) • Type II diabetes mellitus (non-insulin-dependent; reduced responsiveness in insulin targets)

  22. pancreas high liver low pancreas liver Endocrine System Control Regulation of Blood Sugar Feedback islets of Langerhans beta islet cells insulin body cells takeup sugar from blood liver storesglycogen reducesappetite blood sugar level (90mg/100ml) liver releasesglucose triggershunger islets of Langerhansalpha islet cells glucagon

  23. The adrenal glands • Adrenal medulla (catecholamines): •epinephrine & norepinephrine~increase basal metabolic rate (blood glucose and pressure) • Adrenal cortex (corticosteroids): •glucocorticoids(cortisol)~raise blood glucose•mineralocorticoids (aldosterone)~reabsorption of Na+ and K+

  24. The gonads • Steroid hormones: precursor is cholesterol • androgens (testosterone)~ sperm formation; male secondary sex characteristics; gonadotropin • estrogens (estradiol)~uterine lining growth; female secondary sex characteristics; gonadotropin • progestins (progesterone)~uterine lining growth

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