Chapter 15 The Endocrine System


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Chapter 15 The Endocrine System

  1. 1. The Endocrine System <ul><li>What is a hormone? </li></ul><ul><li>Main endocrine glands </li></ul>A. Introduction <ul><li>Pituitary gland </li></ul><ul><li>Thyroid gland </li></ul><ul><li>Parathyroid glands </li></ul><ul><li>Adrenal glands </li></ul><ul><li>Pancreatic islets </li></ul><ul><li>Gonads </li></ul>hypothalamus thyroid gland pancreas (islets) testes pituitary gland thymus gland adrenal glands ovaries
  2. 2. The Endocrine System <ul><li>Endocrine vs. exocrine </li></ul><ul><li>What is a target cell? </li></ul><ul><li>Negative feedback control </li></ul>A. Introduction time [glucose] 110 mg% 90 mg% steady state
  3. 3. The Endocrine System <ul><li>Pituitary gland </li></ul>B. Review of structure and function <ul><li>Controlled by the hypothalamus </li></ul><ul><li>Infundibulum </li></ul><ul><li>Posterior pituitary gland (neurohypophysis) </li></ul><ul><li>Oxytocin </li></ul><ul><li>Anti-diuretic hormone (ADH) </li></ul>
  4. 4. The Endocrine System B. Review of structure and function <ul><li>Growth hormone (GH) </li></ul><ul><li>Thyroid-stimulating hormone (TSH) </li></ul><ul><li>Adrenocorticotrophic hormone (ACTH) </li></ul><ul><li>Follicle-stimulating hormone (FSH) </li></ul><ul><li>Luteinizing hormone (LH) </li></ul><ul><li>Prolactin (PRL) </li></ul><ul><li>Pituitary gland </li></ul>d. Anterior pituitary gland (adenohypophysis)
  5. 5. The Endocrine System 2. Thyroid gland B. Review of structure and function <ul><li>Follicles </li></ul><ul><li>Follicular cells </li></ul><ul><li>Tetraiodothyronine (thyroxine, T4) </li></ul><ul><li>Triiodothyronine (T3) </li></ul>c. Parafollicular cells <ul><li>Calcitonin </li></ul>
  6. 6. The Endocrine System 3. Parathyroid glands B. Review of structure and function <ul><li>Parathyroid hormone (PTH) </li></ul><ul><li>Norepinephrine and epinephrine </li></ul><ul><li>Fight-or-flight </li></ul>4. Adrenal glands <ul><li>Adrenal medulla </li></ul><ul><li>Minheralocorticoids (aldosteorne) </li></ul><ul><li>Glucocorticoids (cortisol, hydrocortisone) </li></ul><ul><li>Gonadocorticoids (estrogens and androgens) </li></ul>b. Adrenal cortex
  7. 7. The Endocrine System 5. Pancreatic islets B. Review of structure and function <ul><li>Insulin </li></ul><ul><li>Glucagon </li></ul><ul><li>Somatostatin </li></ul>
  8. 8. The Endocrine System <ul><li>Hormone secretion stays the same, but receptor numbers on target cells tend to decrease </li></ul><ul><li>Pituitary gland – minimal changes </li></ul><ul><li>Thyroid gland </li></ul>C. Age-related changes <ul><li>T4 production declines by 50% with very old age, but blood levels of thyroxine remain normal </li></ul><ul><li>Gland atrophies with increased nodule formation </li></ul><ul><li>Basal metabolic rate (BMR) decreases </li></ul>
  9. 9. The Endocrine System 4. Parathyroid glands C. Age-related changes <ul><li>No atrophy of glands; some fat deposition </li></ul><ul><li>Post-40, PTH levels in women increase, adding to bone loss problems </li></ul>5. Adrenal glands <ul><li>No atrophy of glands; increased fibrous tissue </li></ul><ul><li>Functional capacity isn’t loss, but there is a moderate decline in adrenocortical hormone secretion </li></ul><ul><li>Secretions of adrenal medulla increase with aging </li></ul>
  10. 10. The Endocrine System 6. Pancreatic islets C. Age-related changes <ul><li>Generally, no decline in insulin </li></ul><ul><li>Decline in function occurs at target cell level (reduced response time in glucose tolerance tests) </li></ul><ul><li>Endocrine disorders are infrequent in old age </li></ul><ul><li>Changes are pathologic rather than age-related </li></ul>D. Age-related dysfunctions
  11. 11. The Endocrine System D. Age-related dysfunctions 3. Diabetes mellitus <ul><li>Essential problem = glucose does enter body cells; blood become hyperglycemia </li></ul><ul><li>Type I (insulin-dependent) = deficient secretion of insulin by islet cells </li></ul><ul><li>Type II (noninsulin-dependent) = decreased sensitivity of target cells to insulin (insulin resistance) </li></ul><ul><li>Clinical features </li></ul><ul><li>Ketosis as a result of excessive lipid use for energy production </li></ul><ul><li>Skin ulcers, glaucoma, cataracts, poor peripheral circulation, retinopathy, neuropathy </li></ul>
  12. 12. The Endocrine System D. Age-related dysfunctions 4. Hypothyroidism <ul><li>5% over age 65 have thyroid hypofunction </li></ul><ul><li>Causes = TSH deficiency, radiation therapy, chronic autoimmune inflammation of the gland, removal of the gland </li></ul><ul><li>Clinical features difficult to diagnose </li></ul><ul><li>Fatigue, depression, mental confusion </li></ul><ul><li>Dry skin, weight gain, constipation </li></ul>
  13. 13. The Endocrine System D. Age-related dysfunctions 5. Stress responses <ul><li>What is stress? </li></ul><ul><li>Subtle stresses for the elderly could be social isolation, loss of spouse, decreased community status </li></ul><ul><li>Activation of the hypothalamo-pituitary-adrenal axis and sympathetic nervous system leads to … </li></ul><ul><li>General adaptation syndrome </li></ul><ul><li>Alarm stage </li></ul><ul><li>Resistance stage </li></ul><ul><li>Exhaustion stage </li></ul>
  14. 14. GENERAL ADAPTATION SYNDROME ALARM RESISTANCE EXHAUSTION STRESS hypothalamus C-RF secretion increased sympathetic activity increased blood pressure ACTH norepinephrine epinephrine --------------------------------------------------------------------------------------------------------------------------------- glucocorticoids increased blood pressure continued decreased inflammatory response increased blood glucose altered protein and fat metaoblism --------------------------------------------------------------------------------------------------------------------------------- decreased immune response + decreased energy reserves decreased resistance to disease hypertension cardiac failure and renal failure DEATH
  15. 15. end The Endocrine System E. Take home messages <ul><li>Structural changes include atrophy, fibrous and fatty deposition, but nothing major </li></ul><ul><li>Blood levels remain within normal ranges, except for gonadal hormones </li></ul><ul><li>Demand for various hormones changes and target cell receptors decrease, altering rates of secretion </li></ul><ul><li>No convincing evidence that age-related changes in endocrine function promote aging </li></ul><ul><li>Plenty of evidence that stress promotes aging </li></ul>