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Introductory Questions #8

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1 Introductory Questions #8
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 ) 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

2 Homeostasis & Osmoregulation

3 The liver is vital in homeostasis
It assists the kidneys by making urea from ammonia breaking down toxic chemicals

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

5 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

6 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

7 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

8 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

9 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

10 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

11 Endocrine System Hormones
Chapter 45. Endocrine System Hormones

12 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

13 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.

14 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

15 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

16 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

17 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 5 Protein is produced.

18 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 Cytoplasm

19 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 Produces an action

20 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

21 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 Enzymatic product

22 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)

23 Major vertebrate hormones (1)

24 Major vertebrate hormones (2)

25 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

26 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)


28 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!

29 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

30 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)

31 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

32 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

33 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 thyroxine

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

35 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

36 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++ Increased blood Ca++

37 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)

38 Any Questions??

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