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Asha Alex Physiology

Types of Cellular Secretion of Hormones Blood Transport of Hormones General Mechanisms of Hormonal Actions. Asha Alex Physiology. What is a HORMONE?. Hormone = chemical messenger produced in the body that interacts w/ receptor in target tissue

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Asha Alex Physiology

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  1. Types of Cellular Secretion of HormonesBlood Transport of Hormones General Mechanisms of Hormonal Actions Asha Alex Physiology

  2. What is a HORMONE? Hormone= chemical messenger produced in the body that interacts w/ receptor in target tissue to cause a change in function of that tissue.

  3. Types of Cellular Secretion • Autocrine • Paracrine • Endocrine • Neuroendocrine • Neural • Pheromonal

  4. Autocrine & Paracrine: The Local Targeters

  5. Endocrine & Neuroendocrine: The Long Distance Travelers

  6. Types of Cellular Secretion of Hormones

  7. Regulation of Hormone Secretion: NEGATIVE FEEDBACK • If hormone A acts to raise the plasma concentration of substrate B, a decrease in substrate B will stimulate the secretion of hormone A. • Whereas an increase in substrate B will suppress secretion of hormone A. • Maintains homeostasis.

  8. Blood Transport of Hormones • When hormones are secreted into blood, many are immediately bound to plasma proteins. • Proteins can recognize hormone specifically & bind it w/high affinity (ex: binding of sex hormones by sex hormone binding globulin- SHBG).

  9. Blood Transport of Hormones • Equilibrium btw free & bound hormone • a fixed proportion of hormone travels free/unbound, while most is carried bound. • Bound hormone is • physiologically inactive • protected from metabolic enzymes in organs (liver) • Drugs, (aspirin) can displace other substances like anticoagulants from their binding sites • may cause hemorrhage.

  10. General Mechanisms of Hormonal Action • Hormones interact w/target cells thru primary interaction w/receptors that recognize the hormones. • Several receptor systems: differ in mechanism & timing. 1) Membrane Receptors 2) Intracellular Receptors

  11. MEMBRANE RECEPTORS Charged ions (peptides, neurotransmitters) bind to receptors on cell membrane conformational change in other membrane proteins activates enzymes in cell Synthesis of second messengers that activate phosphorylating enzymes

  12. Uncharged molecules (steroid hormones) INTRACELLULAR RECEPTORS diffuse into cell & bind to intracellular receptors hormone-receptor complex binds to specific hormone response elements (HREs) on DNA Modulates gene expression in target cell. RNA & protein synthesis altered.

  13. TO WRAP IT UP: • Types of Cell Secretion • Autocrine • Paracrine • Endocrine • Neuroendocrine • Neural • Pheromonal • Blood Transport • binding of hormone to plasma protein • Membrane Receptors • Intracellular Receptors

  14. Bibliography • Endocrinology-At A Glance • Medical Physiology-Guyton

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