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Hormones and Feedback Mechanisms

Hormones and Feedback Mechanisms. Endocrine System. The Endocrine System. Overview Anatomy Glands Hormones. I. A General Overview. ES (endocrine system) and homeostasis Anatomy Glands Hormones Target cells ES as a Control System Hormone + target cell = return to homeostasis.

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Hormones and Feedback Mechanisms

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  1. HormonesandFeedback Mechanisms

  2. Endocrine System

  3. The Endocrine System • Overview • Anatomy • Glands • Hormones

  4. I. A General Overview • ES (endocrine system) and homeostasis • Anatomy • Glands • Hormones • Target cells • ES as a Control System • Hormone + target cell = return to homeostasis

  5. ES and Homeostasis • Homeostasis

  6. II. Anatomy Glands – produce and secrete hormones

  7. C. Hormones • Chemical messenger • Type of Protein • Specific to target cell • Travel in bloodstream

  8. Hormone + Receptor

  9. Hypothalamus RH = Pituitary releasing hormones RIH = Pituitary release inhibiting hormones

  10. Why is the Hypothalamus so Important? • "Directs" pituitary gland

  11. STIMULUS Hypothalamus Releasing Hormone (Release-Inhibiting Hormone) Pituitary Stimulating Hormone Gland Hormone Target

  12. Pituitary gland • MASTER GLAND

  13. 2. Anterior Pituitary Hormones

  14. III.Control of Endocrine Function • Positive • or Negative Feedback mechanisms • Self-regulating system

  15. STIMULUS Hypothalamus Releasing Hormone (Release-Inhibiting Hormone) Pituitary Stimulating Hormone Gland Hormone Target

  16. A. Positive Feedback • Not common • Classic example: Action of OXYTOCIN on uterine muscle during birth.

  17. Positive Feedback • Baby pushes on cervix • Nervous signal to Hypothalamus • Hypothal. manufactures OXY • OXY transported to POSTERIOR PITUITARY & released • OXY stimulates uterine contraction • Loop stops when baby leaves birth canal

  18. B. Negative Feedback • Most common control mechanism • Level of hormone in blood or body’s return to homeostasis shuts off loop at hypothalamus and pituitary

  19. Negative Feedback: Thyroid

  20. Basic Structure of Feedback Loop • Stimulus • Hypothalamus Pituitary • Pituitary Target area • Target area produces change • Change acts negatively or positively on the cycle.

  21. IV. Specific Endocrine Events • Thyroid Hormone • Growth Hormone • Adrenal Cortex Hormones • Sex Steroids

  22. Thyroid • Controls rate of metabolism • Hormones • T3 and T4

  23. Hyperthyroidism and Goiter

  24. Hypersecretion of TSH or TH

  25. Hyposecretion of TH

  26. B. Growth Hormone • Stimulus = Tissue growth/ repair • Hypothalamus releases GHRH • Anterior Pituitary releases GH •  Protein synthesis, growth, etc. • GH and release of somatostatin shuts off GHRH and GH release

  27. What happens with excess GH?

  28. GH as Juvenile

  29. GH as an Adult

  30. How Does Hypersecretion of GH Happen?

  31. GH = pituitary dwarfism

  32. Adrenal Gland • Adrenal gland located atop kidney • Outer part = cortex • Secretes Cortisol (stress), Androgens, Aldosterone (electrolytes) • Inner part = medulla • SNS control • Secretes EPI & NEPI (fight or flight)

  33. Adrenal Insufficiency • Addison’s disease--hyposecretion of cortisol • JFK • Darkened skin (ACTH mimics MSH) • Weight loss, hypoglycemia • Find the anomaly in the feedback loop. • Inability to handle stress

  34. 4. Sex Steroids • Stimulus = low circulating T or E • Hypothalamus = GnRH • Anterior Pituitary = FSH & LH • Gonads produce T and E • High T and E shut off GnRH and FSH/LH

  35. Too many steroids

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