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Endocrine System

Dive into the world of endocrine organs and hormones, exploring their chemical classification, actions, and the major endocrine glands such as the pituitary, thyroid, and adrenal glands. Learn about homeostatic imbalances and how they affect the body's equilibrium. Understand the important role of blood glucose regulation and how disorders like diabetes can impact health.

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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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