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Endocrine System

Endocrine System. Chapter 9. Endocrine Organs. Hormones. Chemical messengers that are released from one tissue and transported through blood to a target tissue. Chemical classification: amino acids, steroids, prostaglandins Receptors on target organ determine effect of hormone

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Endocrine System

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  1. Endocrine System Chapter 9

  2. Endocrine Organs

  3. Hormones • Chemical messengers that are released from one tissue and transported through blood to a target tissue. • Chemical classification: amino acids, steroids, prostaglandins • Receptors on target organ determine effect of hormone • Hormone effects • Membrane permeability • Production of proteins or enzymes • Activation or inactivation of enzymes • Stimulation of cell division • secretion

  4. Hormone Action (Direct) • Lipid soluble • Receptors are in nucleus • Receptor hormone complex binds to DNA • Gene activation • Testosterone and estrogen

  5. Hormone Action (Indirect) • Receptors on plasma membrane • G-Protein Coupled Receptors • 2nd messengers • Epinephrine, calcitonin

  6. Stimulation of Endocrine Glands

  7. Major Endocrine Glands

  8. Pineal Gland • Secretes melatonin • Lack of light stimulates secretion • Regulates sleep/wake cycles (circadian rhythms) • Possible link to fertility

  9. Pituitary Anterior Pituitary Posterior Pituitary

  10. Homeostatic Imbalances • Pituitary Dwarfism (GH hyposecretion)– body is porportional, miniature (4 feet or less) • Gigantism (GH hypersecretion)– body is proportional, giant (8-9 feet) • Acromegly (hypersecretion) – after long bones growth ends, distorted facial features, elongated • Sterility due to hyposecretion of LH and FSH

  11. Pituitary-Hypothalamic Relationship • Hypothalamus regulates or controls pituitary • Portal system which serves anterior lobe • Hypothalamic neurons extending into posterior lobe

  12. Thyroid Gland • Follicle cells secrete thyroglobulin • Regulated by TSH • Thyroglobulin is converted to T3 and T4 in the presence of Iodide • More T4 is secreted however T3 is more effective • Increases metabolism by controlling the breakdown of glucose • Parafollicular cells secrete calcitonin • Regulated by blood calcium levels • Decreases blood calcium levels, stimulating osteoblasts

  13. Homeostatic Imbalances • Goiters – enlarged thyroid due to low levels of iodine, lack of feedback loop to stop production of thyroglobulin • Cretinism (hyposecretion in child) – dwarfism with disproportional body. Large head and trunk with shortened legs • Myxedema (hyposecretion in adult)- slow mentally and physically, obesity, low body temperature • Graves’ Disease (hyperthyroidism) –enlarged thyroid gland, bulging eyes

  14. Parathyroid • Secretes parathyroid hormone (PTH) • Is the most important regulator or controller of blood calcium levels • Regulated by blood calcium levels • Decrease in blood calcium triggers release of PTH • Stimulates osteoclasts to degrade bone • Homeostatic Imbalance –tetany caused by overactive neurons, fragile bones

  15. Calcium Regulation

  16. Adrenal Glands • Structurally and functionally two endocrine glands • Medulla is neural in origin • Secretes catacholamines • Regulated by fear or stress • Short term stress response • Increase: HR, BP, blood glucose, dilates bronchioles • Cortex has three regions • Secretes corticosteroids • Regulated by ACTH • Aldosterone –regulates blood sodium levels • Cortisone & cortisol – increase blood glucose levels, reduce inflammation • Testosterone and estrogen

  17. Stress Response

  18. Homeostatic Imbalances • Addison’s Disease (hyposecretion of glucocorticoids) –electrolyte imbalance, weakness, hypoglycemia, immune suppression, bronze colored skin • Hyperaldosteronism –retention of excessive amounts of Na+ and H20, edema, low K+ effects HR • Cushing’s Syndrome (hypersecretion of glucocorticoids) –high BP, hyperglycemia, fragile bones, fat deposition on upper back, swollen face, immune depression • Masculinization (hypersecretion of testosterone) –masculine body hair, masked in males

  19. Pancreas • Exocrine and endocrine gland • Endocrine gland resides in Islets of Langerhans • Beta cells secrete insulin which lowers blood glucose • Alpha cells secrete glucagonwhich breaks down glycogen (stored glucose) raising blood glucose levels

  20. Blood Glucose Regulation

  21. Homeostatic Imbalances • Diabetes mellitus – high blood sugar • Type I Diabetes (juvenile) –nonfunctioning Beta cells, no insulin is produced • Type II Diabetes (insulin resistant) –nonfunctioning insulin receptors, unable to detect insulin • Three signs of diabetes: polyuria, polydipsia, polyphagia • Ketosis –blood becomes acidic due to breakdown of stored fats, leads to coma and death

  22. Other Endocrine Glands • Thymus –matures T Lymphocytes • Gonads –estrogen and testosterone • Placenta –maintains pregnancy • GI Tract –regulates digestion

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