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ENDOCRINE SYSTEM

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  1. ENDOCRINE SYSTEM Karen LancourPatty Palmietto National Bio Rules National Event Committee Chairman Supervisor – A&P

  2. Endocrine System • Major Endocrine Organs • Hypothalamus • Pituitary gland • Pineal gland • Thyroid gland • Parathyroid gland • Thymus • Adrenal gland • Pancreas • Ovaries • Testes

  3. ENDOCRINE SYSTEM AND HOMEOSTASIS • Homeostasis

  4. Feedback Mechanisms • Stimulus • change in homeostatic environment • signal sent to CNS • Response • signal sent from CNS • produce effect • body returns to homeostasis

  5. GLAND TYPES • Exocrine gland • Ducts • Lumen and surfaces • Endocrine gland • Chemical messengers • Blood stream

  6. Hormones • specific chemical compound • produced by a specific tissue of the body • released in the body fluids • carried to a distant target tissue • affects a pre-existing mechanism • effective is small amounts.

  7. Hormones • Chemical messenger • Secreted by endocrine gland • Specific to target • Activate cellular change • Of 4 different chemical types

  8. Classes of Hormones: peptides – short chains of amino acids (most hormones) pituitary, parathyroid, heart, stomach, liver & kidneys amines - derived from tyrosine and secreted by thyroid and adrenal cortex steroids - lipids derived from cholesterol secreted by the gonads, adrenal cortex, and placenta eicosanoid - Produced from 20-carbon fatty acid, arachadonic acid, produced in all cells except RBCs - Prostaglandins and leukotrienes

  9. Peptide/Protein Hormones • Most common hormone • translated, packaged, & sent • Hydrophilic/Lipophobic • Bind surface receptors at target • Binding mediates signal transduction/2nd messenger system

  10. Protein/Peptide Hormones • Hydrophilic • Large • Can't fit through membrane • Second messenger mechanism of action • Most hormones • Example: Insulin

  11. peptide and amines • Protein hormones (1st messengers) -bind to receptor on target cell triggering 2nd messenger to affect cell’s activity • hormone (1st messenger) does not enter the cellbut binds to receptor on the plasma membrane receptors • hormone-receptor complex activates G protein • generates chemical signal (2nd messenger) – most common is cAMP and IP3 • 2nd messenger chemical signal activates other intracellular chemicals to produce response in target cell

  12. Amine • Synthesized from a single amino acid • Melatonin from tryptophan • Thyroid hormone from tyrosine • Catecholamines (EPI, DA) from tyrosine

  13. Eicosanoid • Produced from 20-carbon fatty acid, arachadonic acid • Produced in all cells except RBCs • 2nd messenger • Prostaglandins and leukotrienes • inflammation

  14. Hormone + Receptor

  15. Steroid Hormones • Small • Hydrophobic/Lipophilic • Travel in blood w/carrier • Cytoplasmic or nuclear receptors • change protein synthesis • Example: estradiol

  16. Steroid Hormones • Steroid hormones - bind to receptors within target cell and influence cell activity by acting on specific genes • hormone diffuses freely into cell where cytoplasmic and/ or nuclear proteins serve as receptors • hormone binds to receptor (hormone-receptor complex) • complex bonds to steroid response element (sections of DNA receptive to the hormone-receptor complex • hormone-receptor complex acts as transcription factor to turn target genes “on” or “off”

  17. Hormone + Receptor

  18. The H-P-AHypothalamic-Pituitary Axis • Most feedback loops run through this axis • HPA mediates growth, metabolism, stress response, reproduction. • is secondarily in charge of almost everything else.

  19. Neurosecretory Cells Specialized neurons Synthesize and secrete hormones Extend from HYPOTHALAMUS to POSTERIOR PITUITARY

  20. Neurosecretory cells in Hypothalamus • Nuclei synthesize and secrete hormones • Neuronal connection to POSTERIOR pituitary • Antidiuretic Hormone (ADH), Oxytocin

  21. Hypothalamus (general) Connection to pituitary Neuronal to POSTERIOR PITUITARY Endocrine to ANTERIOR PITUITARY RH = Pituitary releasing hormones RIH = Pituitary release inhibiting hormones

  22. Hypothalamus • Secretes regulatory homones • RH • RIH • "Directs" pituitary

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

  24. Hypothalamic Hormomes • Release Inhibiting Hormones • Somatostatin • Prolactin release inhibiting hormone-PIH • Releasing Hormones • Thyrotropin releasing hormone-TRH • Growth hormone releasing hormone-GHRH

  25. Posterior Pituitary Hormones • Manufactured in Hypothalamus, • released from Post. Pit. • Oxytocin • Target = smooth ms. Uterus and Breast (&brain) • Function = labor and delivery, milk ejection,(pair bonding) • ADH (Vasopressin AVP) • Target = kidneys • Function = water reabsorption

  26. Pituitary gland • MASTER GLAND • Anterior and posterior portions • Posterior connected to hypothalamus by infundibulum • Anterior connected via blood stream

  27. Anterior Pituitary Hormones

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

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

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

  31. 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

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

  33. Negative Feedback: Thyroid

  34. Basic Structure of Feedback Loop • Environmental Stimulus • Stimulates Control Center (Brain-hypothalamus) • Hypothalamic hormones stimulate Pituitary • Pituitary hormone stimulate Target area • Target area produces change • Change acts negatively or positively on the cycle.

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

  36. Endocrine Disorders Hyposecretiondisorders are caused by too little hormone – they can be treated by addition of the hormone Hypersecretion disorders are caused by too much hormone – these are much harder to treat

  37. Thyroid Hormone •  T3 & T4 stim. Or environmental stim. Hypothalamus • TRH stim. Anterior Pituitary • TSH stim. Thyroid •  T3 & T4 shuts off TRH and TSH production

  38. Thyroid Problems • What would happen if the thyroid could no longer produce T3 and T4? • No negative feedback to hypothalamus and anterior pituitary

  39. Hypersecretion of TSH or TH

  40. Hyposecretion of TH

  41. 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

  42. GH as Juvenile

  43. 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)

  44. 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

  45. 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

  46. Too many steroids

  47. Diseases of the Endocrine System • Diabetes – increased levels of glucose in blood • Hypoglycemia - low blood sugar • Graves Disease – overactive thyroid • Goiter – enlarged thyroid gland