BIOH111. o Cell Module o Tissue Module o Skeletal system o Muscle system o Nervous system o Endocrine system o Integumentary system

Transcription

1 BIOH111 o Cell Module o Tissue Module o Skeletal system o Muscle system o Nervous system o Endocrine system o Integumentary system Endeavour College of Natural Health endeavour.edu.au 1

2 Textbook and required/recommended readings o Principles of anatomy and physiology. Tortora et al; 14 th edition: Chapter 18 Endeavour College of Natural Health endeavour.edu.au 2

3 BIOH111 ENDOCRINE SYSTEM MODULE o Session 21 (Lectures 41 and 42) Hormones, hormone receptors and molecular basis of hormone action and regulation o Session 22 (Lectures 43 and 44) Hypothalamus and pituitary, thyroid and parathyroid glands structure and function o Session 23 (Lectures 45 and 46) - Pineal, thymus, adrenal, pancreas and reproductive glands structure and function Endeavour College of Natural Health endeavour.edu.au 3

4 BIOH111 Lectures 41 and 42 Hormones, hormone receptors and molecular basis of hormone action and regulation Department of Bioscience endeavour.edu.au

5 Objectives Lecture 41: Hormones List different chemical classes and types of hormones Comment on hormone interactions Comment on regulation of hormone action from perspective of hormone itself Lecture 42: Hormone receptors Describe how each chemical class of hormones exert their functions Comment on regulation of hormone action from perspective of hormone receptor Endeavour College of Natural Health endeavour.edu.au 5

6 NEUROENDOCRINE SYSTEM o The nervous and endocrine systems act as a coordinated interlocking super system Endocrine system: exerts control by releasing mediator molecules called hormones that are released into the bloodstream action may take hours Nervous system: exerts controls body through nerve impulses which result in hormone release or neurotransmitter release Action takes milliseconds Parts of the nervous system stimulate or inhibit the release of hormones. Hormones may promote or inhibit the generation of nerve impulses. Endeavour College of Natural Health endeavour.edu.au 6

7 cells tissue organ GLANDS Gland is a single cell or a mass of epithelial cells adapted for secretion. 2 types: o Endocrine glands are ductless; secrete hormones into the interstitial fluid and then diffuse into the bloodstream. o Exocrine glands secrete their products into ducts that empty at the surface of covering and lining epithelium (e.g. skin surface or lumen of a hollow organ); classified based on their structure and function Endeavour College of Natural Health endeavour.edu.au 7

8 cells tissue organ ENDOCRINE GLANDS Endeavour College of Natural Health endeavour.edu.au 8

9 HORMONE SECRETION AND ACTION Endeavour College of Natural Health endeavour.edu.au 9

10 HORMONES o Structure: lipid- and water-soluble o Function: hormones have powerful effects even when present in very low concentrations and help regulate: extracellular fluid metabolism biological clock contraction of cardiac & smooth muscle glandular secretion some immune functions growth & development reproduction Endeavour College of Natural Health endeavour.edu.au 10

11 LIPID-SOLUBLE HORMONES o Must attach to transport proteins - why? o Steroids lipids derived from cholesterol on smooth ER different functional groups attached to structure core provides specificity o Thyroid hormones tyrosine ring plus attached iodines are lipid-soluble o Nitric oxide gas Endeavour College of Natural Health endeavour.edu.au 11

12 WATER-SOLUBLE HORMONES o Circulate in free form in blood o Amine, peptide and protein hormones modified amino acids or amino acids put together serotonin, melatonin, histamine, epinephrine some glycoproteins o Eicosanoids derived from arachidonic acid (fatty acid) prostaglandins or leukotrienes Endeavour College of Natural Health endeavour.edu.au 12

13 HORMONE TYPES 1. Circulating hormones travel in blood and act on distant target cells 2. Local hormones act locally without entering the bloodstream; 2 types: 1. paracrine 2. autocrine Endeavour College of Natural Health endeavour.edu.au 13

14 CONTROL OF HORMONE SECRETION o Regulated by signals from nervous system, chemical changes in the blood or by other hormones; secretion controlled by feedback loops: 1. Negative feedback control (most common) decrease/increase in blood level is reversed E.g.?? 2. Positive feedback control change produced by the hormone causes more hormone to be released E.g.?? Endeavour College of Natural Health endeavour.edu.au 14

15 HORMONAL INTERACTIONS o Responsiveness of a target cell to a hormone depends on: 1. Concentration of the hormone 2. Abundance of the hormone receptors on target cell (next lecture) 3. Influences exerted on the same cell by other hormones; interactions of 2 hormones can exert one or these effects: a) Permissive effect: second hormone, strengthens the effects of the first b) Synergistic effect: two hormones acting together for greater effect c) Antagonistic effects: two hormones with opposite effects Endeavour College of Natural Health endeavour.edu.au 15

16 Disorders of feeback control involve either hyposecretion or hypersecretion of a hormone. In groups of 3-4 find example of each and comment how this influences overall body homeostasis. In groups of 3-4: research examples of each hormonal interaction effects and comment on effects these would exert on overall body homeostasis if they were not balanced properly. Endeavour College of Natural Health endeavour.edu.au 16

17 Objectives Lecture 41: Hormones List different chemical classes and types of hormones Comment on hormone interactions Comment on regulation of hormone action from perspective of hormone itself Lecture 42: Hormone receptors Describe how each chemical class of hormones exert their functions Comment on regulation of hormone action from perspective of hormone receptor Endeavour College of Natural Health endeavour.edu.au 17

18 HORMONE SECRETION AND ACTION Endeavour College of Natural Health endeavour.edu.au 18

19 HORMONE RECEPTORS o Expression of a receptor on only subset of cells confers specificity of the hormone action so each cell may respond differently to the same hormone o Structure: 2 types: 1. Transmembrane receptors: found on cell surface and bind water-soluble hormones 2. Nuclear receptors: found in the nucleus and bind lipid-soluble hormones o General function: hormone/receptor interaction causes intracellular events that lead to: synthesis of new molecules, change in membrane permeability or alteration in reaction rates Endeavour College of Natural Health endeavour.edu.au 19

20 Once signalling molecule interacts with its receptor it starts cell signalling cascades Cell signalling is a process of converting extracellular signal (signalling molecule) into intracellular response (gene transcription) via transduction cascade initiated by signal+receptor engagement. REVISION Endeavour College of Natural Health endeavour.edu.au 20

21 TRANSMEMBRANE RECEPTORS 1. hormone (1 st messenger) interacts with its membrane receptor 2. activated receptor activates membrane G-protein which turns on adenylate cyclase 3. adenylate cyclase converts ATP into cyclic AMP (2 nd messenger) which activates protein kinases 4. protein kinases phosphorylate enzymes which catalyze reactions that produce specific physiological response Signalling cascade signal amplification Endeavour College of Natural Health endeavour.edu.au 21

22 Signal amplification 1. single molecule of hormone binds to receptor 2. activates 100 G-proteins 3. each G-protein activates an adenylate cyclase molecule which then produces 1000 camp 4. each camp activates a protein kinase, which may act upon 1000 s of substrate molecules e.g. one molecule of epinephrine may result in breakdown of millions of glycogen molecules into glucose molecules Signalling cascade signal amplification Endeavour College of Natural Health endeavour.edu.au 23

23 SECOND MESSENGERS Hormone+receptor Increase camp synthesis e.g. ADH, TSH, ACTH, glucagon and epinephrine Decrease in camp level e.g. growth hormone inhibiting hormone o NOTE: 1. Other substances can act as second messengers (e.g. calcium ions and cgmp) 2. Same hormone may use different second messengers in different target cells Endeavour College of Natural Health endeavour.edu.au 24

24 Response regulation 1. hormone interacts with its membrane receptor. 2. activated receptor activates membrane G-protein which turns on adenylate cyclase 3. adenylate cyclase converts ATP into cyclic AMP which activates protein kinases 4. phosphodiesterase inactivates camp quickly; cell response is turned off unless new hormone molecules arrive Endeavour College of Natural Health endeavour.edu.au 25

25 HORMONE RECEPTOR REGULATION o Receptors are constantly turned over why? range of ,000 receptors / target cell o 2 ways of regulation: 1. Down-regulation of receptor: excess hormone leads to a decrease in number of receptors by endocytosis and degradation decreases sensitivity of target cell to hormone 2. Up-regulation of receptor: deficiency of hormone leads to an increase in the number of receptors target tissue becomes more sensitive to the hormone Endeavour College of Natural Health endeavour.edu.au 26

26 NUCLEAR RECEPTORS 1. hormone diffuses through phospholipid bilayer and into cell 2. Interacts with a nuclear receptor 3. Complex is able to interact with DNA and turn on/off specific genes 4. Overall effect: mrna directs synthesis of new proteins which alter activity of that cell Endeavour College of Natural Health endeavour.edu.au 27

27 Vibrio cholera produces a cholera toxin which causes watery diarrhea that can lead to excessive dehydration and sometimes death. In groups of 3-4: investigate cellular and molecular mechanism of action this toxin takes to cause diarrhea. Endeavour College of Natural Health endeavour.edu.au 28

28 In groups of 3-4: Progesterone is released by ovaries straight after the egg is released and binds to its receptor in the uterus lining. If egg is fertilised, egg is implanted and uterus lining stays thick. If no fertilisation occurs progesterone levels decrease and menstrual cycle occurs where lining is shed. What happens if you block the progesterone/progesterone receptor interaction and egg is fertilised and implanted? What situation would you use the knowledge of this mechanism to deliberately block it? Endeavour College of Natural Health endeavour.edu.au 30

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