Homeostasis : regulation of internal environment

1. Homeostasis: regulation of internal environment • Thermoregulation internal temperature • Osmoregulation solute and water balance • Excretion nitrogen containing waste

2. Regulation of body temperature • Thermoregulation • 4 physical processes: • Conduction~transfer of heat between molecules of body and environment • Convection~transfer of heat as water/air move across body surface • Radiation~transfer of heat produced by organisms • Evaporation~loss of heat from liquid to gas • Sources of body heat: • Ectothermic: determined by environment • Endothermic: high metabolic rate generates high body heat

3. Let Sleeping Bears Lie • Bears don’t technically hibernate • They do enter a dormant state, when their body temperature drops by several degrees • Bears are endotherms • Endothermic animals derive most of their body heat from metabolism • Ectothermic animals warm themselves mainly by absorbing heat from their surroundings

4. Thermoregulation maintains the body temperature within a tolerable range • Osmoregulation controls the gain and loss of water and dissolved solutes • Excretion is the disposal of metabolic wastes • Dormant bears have internal homeostatic mechanisms that compensate for fluctuations in the external environment

5. Heat is gained or lost in four ways • Body temperature regulation requires adjustment to heat gained from or lost to an animal’s environment Convection Radiation Evaporation Conduction Figure 25.1

6. Fur and feathers help the body retain heat • Shivering, as these honeybees are doing, also increases metabolic heat production • Hormonal changes may increase heat production by raising the metabolic rate Figure 25.2A

7. Regulation during environmental extremes • Torpor~ low activity; decrease in metabolic rate • 1- Hibernation long term or winter torpor (winter cold and food scarcity); bears, squirrels • 2- Estivation short term or summer torpor (high temperatures and water scarcity); fish, amphibians, reptiles • Both often triggered by length of daylight

8. Chapter 45. Endocrine System Hormones

9. 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

10. 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

11. 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

12. 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

13. 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

14. 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.

15. 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

16. 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

17. 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

18. 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

19. Endocrine system • Ductless glands release hormones into blood • Tropic hormones= a hormone that has another endocrine gland as a target Duct glands = exocrine (tears, salivary)

20. Major vertebrate hormones (1)

21. Major vertebrate hormones (2)

22. 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

23. 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

25. 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

26. 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

27. Regulating blood sugar levels • 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)

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

29. Regulating blood osmolarity If amount of dissolved material in blood is 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

30. 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

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

32. 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

33. 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++

34. 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

35. Homeostasis: regulation of internal environment • Thermoregulation internal temperature • Osmoregulation solute and water balance • Excretion nitrogen containing waste

36. Regulation of body temperature • Thermoregulation • 4 physical processes: • Conduction~transfer of heat between molecules of body and environment • Convection~transfer of heat as water/air move across body surface • Radiation~transfer of heat produced by organisms • Evaporation~loss of heat from liquid to gas • Sources of body heat: • Ectothermic: determined by environment • Endothermic: high metabolic rate generates high body heat

37. Let Sleeping Bears Lie • Bears don’t technically hibernate • They do enter a dormant state, when their body temperature drops by several degrees • Bears are endotherms • Endothermic animals derive most of their body heat from metabolism • Ectothermic animals warm themselves mainly by absorbing heat from their surroundings

38. Thermoregulation maintains the body temperature within a tolerable range • Osmoregulation controls the gain and loss of water and dissolved solutes • Excretion is the disposal of metabolic wastes • Dormant bears have internal homeostatic mechanisms that compensate for fluctuations in the external environment

39. Heat is gained or lost in four ways • Body temperature regulation requires adjustment to heat gained from or lost to an animal’s environment Convection Radiation Evaporation Conduction Figure 25.1

40. Fur and feathers help the body retain heat • Shivering, as these honeybees are doing, also increases metabolic heat production • Hormonal changes may increase heat production by raising the metabolic rate Figure 25.2A

41. Regulation during environmental extremes • Torpor~ low activity; decrease in metabolic rate • 1- Hibernation long term or winter torpor (winter cold and food scarcity); bears, squirrels • 2- Estivation short term or summer torpor (high temperatures and water scarcity); fish, amphibians, reptiles • Both often triggered by length of daylight