Signalling mechanism of hormones and neuroendocrine


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Signalling mechanism of hormones and neuroendocrine

  1. 1. Signalling mechanism of hormones Dr. Sadaf Mumtaz 27-1-11
  2. 3. Broad Classification (Structure) Hydrophillic Lipophillic Proteins, peptide hormones & catecholamines Steroid and thyroid hormones Primarily act through second messenger system Activate genes on binding with receptors in the nucleus Circulate mainly dissolved in the plasma Largely bound to plasma proteins
  3. 4. Synthesis of hormones <ul><li>Polypeptides and protein hormones ---- Size 3AA to 200AA </li></ul>
  4. 5. Steroid hormones <ul><li>Cholesterol esters stored in cytoplasmic vacuoles can be mobilized for steroid synthesis </li></ul>
  5. 6. Location for different types of hormone receptors
  6. 7. Amine Hormones <ul><li>Formed by the action of enzymes in the cytoplasmic compartment of glandular cells </li></ul><ul><li>Thyroid gland </li></ul><ul><li>Epinephrine and nor epinephrine </li></ul>Thyroglobulin Thyroxine binding globulin Plasma
  7. 8. <ul><li>What are trophic hormones </li></ul><ul><ul><li>A hormone that has its primary function the regulation of hormone secretion by another endocrine gland </li></ul></ul><ul><li>What is </li></ul><ul><ul><li>Permissiveness </li></ul></ul><ul><ul><ul><li>One hormone must be present in adequate amounts for the full exertion of another hormone’s effect. </li></ul></ul></ul><ul><ul><li>Synergism </li></ul></ul><ul><ul><ul><li>The combined effect is greater then the sum of the separate effects. </li></ul></ul></ul><ul><ul><li>Antagonism </li></ul></ul><ul><ul><ul><li>When one hormone causes the loss of another hormone’s receptors, reducing the effectiveness of the second hormone </li></ul></ul></ul>
  8. 9. Onset of hormone secretion and action
  9. 10. Feedback control of hormone secretion <ul><li>Negative feedback </li></ul><ul><ul><li>Through hormone or one of its product </li></ul></ul><ul><ul><li>Controlled variable </li></ul></ul><ul><li>Positive feedback </li></ul>
  10. 11. Cyclic variations
  11. 13. Mechanism of activation of GPCRs
  12. 14. Enzyme linked hormone receptors
  13. 15. Second messenger mechanisms
  14. 16. ER SOC TRPC1,4 IP3R RhoA-GTP RhoGDI-P Rhokinase MLC-P ROC TRPC3,6,7 Ca 2+ calmodulin Ca 2+ CaM CamKinase II Inactive MLCK Active MLCK Phosphorylation MLC Dephosphorylation MLCP Inactive Phosphorylated MLCP (PP1c-MYPT1) GPCR RTK Agonist PLC PIP2 DAG IP3 Ca 2+ PKC Ca 2+ CP1-17 CP1-17-P PP2A MT dissassembly Actin polymerization Stress fibre formation Activation mechanism of ECs MLCP
  15. 18. Measurement of hormone concentration in the Blood <ul><li>Radioimmunoassay </li></ul><ul><li>Enzyme linked immunosorbent assay (ELISA) </li></ul>Radioisotope Antibody Hormone Enzyme Antibody Hormone
  16. 19. Radioimmunoassay Antibody Fluid from animal containing hormone + + (Hormone + Radioisotope) Competition for antibody binding Equilibrium Antibody complex separated Quantity of radioactive hormone complex is measured by radioactive counting technique
  17. 20. ELISA
  18. 21. <ul><li>Hormones </li></ul><ul><li>a) are secreted by exocrine glands. </li></ul><ul><li>b) act only on neighboring cells. </li></ul><ul><li>c) are always peptides. </li></ul><ul><li>d) are secreted into the blood. </li></ul><ul><li>Hormone receptors: </li></ul><ul><li>a) have a high affinity for their natural ligand. </li></ul><ul><li>b) are always linked to G proteins. </li></ul><ul><li>c) are lipids. </li></ul><ul><li>d) are always located in the plasma membrane of their target cells </li></ul><ul><li>G protein activation: </li></ul><ul><li>a) leads to changes in gene expression. </li></ul><ul><li>b) always causes an increase in cyclic AMP. </li></ul><ul><li>c) leads to the generation of second messengers. </li></ul><ul><li>d) always results in a decrease in cyclic AMP </li></ul><ul><li>Steroid hormones such as aldosterone: </li></ul><ul><li>a) bind to nuclear receptors to regulate gene expression. </li></ul><ul><li>b) activate G protein cascades. </li></ul><ul><li>c) activate receptors on the cell membrane. </li></ul><ul><li>d) directly regulate protein synthesis </li></ul>
  19. 22. Pituitary hormones and its control by hypothalamus
  20. 23. Hypothalamic releasing and inhibiting hormones control anterior pituitary secretion TRH GnRH CRH GHRH GHIH PIH
  21. 25. <ul><li>If the pituitary gland is removed from its normal position beneath hypothalamus and transplanted to some other part of the body </li></ul><ul><ul><li>What will happen to its rate of secretion of different hormones? </li></ul></ul>
  22. 26. Thank you