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Introductory Questions #8 1) 2) 3) 4) 5) Name the nine major endocrine glands found in the body. Which one is called the “master gland”? Name three major local regulators that act on nearby target cells. (pgs. 947-948) Name three key molecules that play a role in the signal transduction pathway (typical reactions in the endocrine system). How is the anterior part of the pituitary gland different from the posterior part? Name the hormones secreted from each area. Which region secretes fewer types of hormones? Using the table on pg. 949, name the hormone(s) that: -Raises blood-calcium levels -maintains metabolic processes Homeostasis & Osmoregulation Chapter The liver is vital in homeostasis • It assists the kidneys by – making urea from ammonia – breaking down toxic chemicals Homeostasis: regulation of internal environment • Thermoregulation internal temperature • Osmoregulation solute and water balance • Excretion nitrogen containing waste 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 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 • Dormant bears have internal homeostatic mechanisms that compensate for fluctuations in the external environment – 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 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 • Hormonal changes may increase heat production by raising the metabolic rate – Fur and feathers help the body retain heat – Shivering, as these honeybees are doing, also increases metabolic heat production Figure 25.2A 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 Chapter 45. Endocrine System Hormones AP Biology 2004-2005 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 2004-2005 growth hormones 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 AP Biology 2004-2005 Regulation by chemical messengers Neurotransmitters released by neurons Hormones release by endocrine glands Endocrine gland Axon Neurotransmitter Hormone carried by blood Receptor proteins AP Biology Target cell 2004-2005 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 AP Biology 2004-2005 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 2004-2005 Action of steroid (lipid) hormones Cytoplasm S Steroid S hormone Blood plasma S 1 Protein carrier Plasma membrane 1 Steroid hormone (S) passes 2 through plasma membrane. 2 Inside target cell, the steroid hormone binds to a specific receptor protein in the cytoplasm or nucleus. 3 Hormone-receptor complex enters nucleus & binds to DNA, causing gene transcription 4 Protein synthesis is induced. 5 Protein is produced. 2004-2005 4 S DNA Nucleus AP Biology 3 mRNA 5 Protein 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 2004-2005 Action of protein hormones 1 Protein hormone activates enzyme G protein cAMP Receptor protein 3 2 ATP GTP Cytoplasm AP Biology activates enzyme activates enzyme 4 Produces an action protein messenger cascade 2004-2005 Action of epinephrine (adrenalin) Liver cell 1 Epinephrine activates adenylyl cyclase adrenal gland G protein Receptor protein cAMP 2 3 ATP GTP activates protein kinase-A activates phosphorylase 4 released to blood Cytoplasm AP Biology Glycogen Glucose 2004-2005 Benefits of a 2° messenger system 1 Signal molecule Receptor protein Activated adenylyl cyclase Not yet activated 2 Amplification 4 Amplification 3 GTP cAMP 5 G protein Protein kinase 6 Amplification Amplification! AP Biology Enzyme 7 Amplification Enzymatic product 2004-2005 Endocrine system Ductless glands release hormones into blood Tropic hormones= a hormone that has another endocrine gland as a target Duct glands = exocrine AP Biology (tears, salivary) 2004-2005 Major vertebrate hormones (1) AP Biology 2004-2005 Major vertebrate hormones (2) AP Biology 2004-2005 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” AP Biology endocrine system secretes broad range of hormones regulating other glands 2004-2005 Hypothalamus Thyroid-stimulating Antidiuretic Hormone Posterior hormone (TSH) pituitary (ADH) Thyroid gland 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 2004-2005 AP Biology 2004-2005 Homology in hormones What does this tell you about these hormones? same gene family prolactin mammals milk production AP Biology birds fat metabolism fish amphibians salt & water balance metamorphosis & maturation growth hormone growth & development 2004-2005 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) Hormones2004-2005 – 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) AP Biology Regulating blood sugar levels beta islet cells pancreas Islets of Langerhans Alpha cells: •glucagon~ raises blood glucose levels Beta cells: •insulin~ lowers blood glucose levels Type I diabetes mellitus (insulindependent; autoimmune disorder) Type II diabetes mellitus (non-insulindependent; reduced responsiveness in insulin targets) - triggers release of glucose by liver - stimulates appetite AP Biology - triggers uptake of glucose by body cells - triggers storage in liver - depresses appetite pancreas alpha islet cells 2004-2005 Regulating blood osmolarity If amount of dissolved material in blood is too high, need to dilute blood Dehydration Osmotic concentration of blood increases Negative feedback Osmoreceptors Negative feedback ADH synthesized in hypothalamus ADH Increased water retention AP Biology Lowers blood volume & pressure Reduced urine volume ADH released from posterior pituitary into blood Increased vasoconstriction leading to higher blood pressure 2004-2005 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 2004-2005 Goiter Iodine deficiency causes thyroid to enlarge as it tries to produce thyroxine AP Biology 2004-2005 Thyroxine secretion rate Homology in hormones –35 Thyroxine stimulates metamorphosis in amphibians TRH TSH Thyroxine TRH rises –30 –25 –20 –15 –10 –5 0 +5 +10 Days from emergence of forelimb AP Biology 2004-2005 Regulating blood calcium levels Thyroid Low blood Ca++ – Negative feedback Increased absorption of Ca++ from intestine due to PTH activation of Vitamin D AP Biology Parathyroids Parathyroid hormone (PTH) Reabsorption of Ca++ & excretion of PO4 Increased blood Ca++ Osteoclasts dissolve CaPO4 crystals in bone, releasing Ca++ 2004-2005 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 Any Questions?? AP Biology 2005-2006