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Presentation 19 - Chemical Signals In Animals

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Presentation 19 - Chemical Signals In Animals

  1. 2. Key concepts <ul><li>Hormones are compounds produced in one part of the body and transported to another location to produce specific responses; small amount s can induce substantial responses. </li></ul><ul><li>Chemical signals produced by the body are mostly produced by glands . </li></ul><ul><li>Hormones either affect a target effector organ directly or via the signal transduction pathway . </li></ul><ul><li>Effects of hormones vary depending on whether they bind to a receptor in the plasma membrane or within the nucleus of a cell. </li></ul><ul><li>Action of hormones is controlled by feedback mechanisms . </li></ul><ul><li>Hormones are classified by mode of transport or through chemical composition . </li></ul><ul><li>Diseases in the endocrine system occur when levels of hormones released are at an abnormal level or when receptors of that particular hormone are damaged. </li></ul>
  2. 3. Endocrine system <ul><li>Hormone-secreting cells </li></ul><ul><li>Chemical signals secreted into body fluids, eliciting responses in target cells </li></ul><ul><li>Functions with NS in maintaining homeostasis </li></ul><ul><li>Effects are slower and longer-lasting </li></ul>
  3. 4. Maintenance of Homeostasis by the ES and NS <ul><li>Neurosecretory cells – nerve cells that secrete hormones into bloodstream (eg. epinephrine ) </li></ul><ul><li>Feedback regulation </li></ul><ul><ul><li>Positive feedback </li></ul></ul><ul><ul><ul><li>Suckling  release of oxytocin  milk secretion </li></ul></ul></ul><ul><ul><li>Negative feedback </li></ul></ul><ul><ul><ul><li>Control of blood calcium and glucose levels </li></ul></ul></ul>
  4. 5. Invertebrate Endocrine Systems <ul><li>Hydra –control method of reproduction </li></ul><ul><li>Mollusks –controls egg-laying </li></ul><ul><li>Arthropods – extensive endocrine systems for molting and maturity </li></ul><ul><ul><li>Ecdysone  molting and promotion of adult features </li></ul></ul><ul><ul><li>Brain hormone (BH)  regulates production of ecdysone </li></ul></ul><ul><ul><li>Juvenile hormone (JH)  retention of larval characteristics </li></ul></ul>
  5. 6. Chemical signals and their modes of action most peptides, proteins and glycoproteins steroids and thyroid hormones
  6. 7. Importance of signal transduction pathways <ul><li>1) Different pathways in different cells  different responses to the same signal </li></ul><ul><li>2) Amplification of the single signal allows small amounts of hormones to have a large effect </li></ul>
  7. 8. Vertebrate endocrine systems <ul><li>Hypothalamus integrates endocrine and nervous functions </li></ul><ul><li>Neurosecretory cells of hypothalamus produce trophic/tropic hormones </li></ul><ul><ul><li>Stored and secreted by posterior pituitary </li></ul></ul><ul><ul><li>Affect anterior pituitary’s release of own hormones </li></ul></ul>
  8. 9. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
  9. 10. Table 45.1 (continued ) Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
  10. 11. Feedback control loops: a closer look <ul><li>Regulation of thyroid hormones </li></ul><ul><li>Regulation of glucose in the blood </li></ul>
  11. 12. Hormones and the female reproductive cycle
  12. 13. Hormones control the reproductive cycle of human females
  13. 14. Performance-enhancing drugs