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

Excretion is the disposal of metabolic wastes 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

Fur and feathers help the body retain heat 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

Endocrine System Hormones Chapter 45. Endocrine System Hormones 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 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 Hormones coordinate slower but longer–acting responses to stimuli such as stress, dehydration, and low blood glucose levels. Hormones also regulate long–term developmental processes by informing different parts of the body how fast to grow or when to develop the characteristics that distinguish male from female or juvenile from adult. Hormone–secreting organs, called endocrine glands, are referred to as ductless glands because they secrete their chemical messengers directly into extracellular fluid. From there, the chemicals diffuse into the circulation. 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 2004-2005 Target cell

Classes of Hormones Protein-based hormones Lipid-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 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 bind to DNA as transcription factors 2004-2005

Action of steroid (lipid) hormones Cytoplasm Blood plasma Steroid hormone S S 1 Protein carrier S 2 Plasma membrane 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 2004-2005 5 Protein is produced.

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 Target protein Nucleus 2004-2005 Cytoplasm

Action of protein hormones 1 Protein hormone activates enzyme G protein Receptor protein cAMP 3 2 ATP activates enzyme protein messenger cascade GTP activates enzyme 4 Cytoplasm 2004-2005 Produces an action

Action of epinephrine (adrenalin) Liver cell 1 Epinephrine activates adenylyl cyclase adrenal gland G protein Receptor protein cAMP 3 2 ATP activates protein kinase-A GTP activates phosphorylase 4 released to blood Cytoplasm Glycogen Glucose 2004-2005

Benefits of a 2° messenger system 1 Receptor protein Activated adenylyl cyclase Signal molecule Not yet activated 2 Amplification 4 Amplification cAMP 3 5 GTP G protein Protein kinase 6 Amplification Amplification! Enzyme 7 Amplification 2004-2005 Enzymatic product

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) 2004-2005

Major vertebrate hormones (1) 2004-2005

Major vertebrate hormones (2) 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” endocrine system secretes broad range of hormones regulating other glands 2004-2005

Melanocyte-stimulating hormone Thyroid gland Hypothalamus Anterior pituitary Gonadotropic hormones: Follicle- stimulating hormone (FSH) & luteinizing hormone (LH) Mammary glands in mammals Muscles of uterus Kidney tubules Posterior Thyroid-stimulating Hormone (TSH) Antidiuretic hormone (ADH) Adrenal cortex Bone and muscle Testis Ovary Melanocyte in amphibian Adrenocorticotropic hormone (ACTH) Melanocyte-stimulating hormone (MSH) Oxytocin Prolactin (PRL) Growth hormone (GH) 2004-2005

2004-2005

metamorphosis & maturation Homology in hormones What does this tell you about these hormones? prolactin same gene family growth hormone mammals birds fish amphibians milk production fat metabolism salt & water balance metamorphosis & maturation growth & development The most remarkable characteristic of prolactin (PRL) is the great diversity of effects it produces in different vertebrate species. For example, prolactin stimulates mammary gland growth and milk synthesis in mammals; regulates fat metabolism and reproduction in birds; delays metamorphosis in amphibians, where it may also function as a larval growth hormone; and regulates salt and water balance in freshwater fishes. This list suggests that prolactin is an ancient hormone whose functions have diversified during the evolution of the various vertebrate groups. Growth hormone (GH) is so similar structurally to prolactin that scientists hypothesize that the genes directing their production evolved from the same ancestral gene. Gene duplication! 2004-2005

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) 2004-2005 Hormones

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)

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 2004-2005 alpha islet cells

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 Osmoreceptors Negative feedback 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 2004-2005

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 The thyroid gland produces two very similar hormones derived from the amino acid tyrosine: triiodothyronine (T3), which contains three iodine atoms, and tetraiodothyronine, or thyroxine (T4), which contains four iodine atoms. In mammals, the thyroid secretes mainly T4, but target cells convert most of it to T3 by removing one iodine atom. Although both hormones are bound by the same receptor protein located in the cell nucleus, the receptor has greater affinity for T3 than for T4. Thus, it is mostly T3 that brings about responses in target cells. tyrosine iodine 2004-2005 thyroxine

Goiter Iodine deficiency causes thyroid to enlarge as it tries to produce thyroxine 2004-2005

Homology in hormones Thyroxine stimulates metamorphosis in amphibians TRH TSH Thyroxine Thyroxine secretion rate TRH rises –35 –30 –25 –20 –15 –10 –5 +5 +10 Days from emergence of forelimb 2004-2005

Regulating blood calcium levels Thyroid Low blood Ca++ Parathyroids – Parathyroid hormone (PTH) Negative feedback PTH activates Vitamin D into hormone that enables calcium absorption from intestines. This is why Vitamin D deficiency causes rickets = poor bone formation 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++ 2004-2005 Increased blood Ca++

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)

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

Excretion is the disposal of metabolic wastes 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

Fur and feathers help the body retain heat 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