1. Mechanisms of Hormonal Regulation Chapter 17

2. The Endocrine System Functions –Differentiation of reproductive and CNS in fetus –Stimulation of growth and development –Coordination of the male and female reproductive system –Maintenance of internal environment –Adaptation to emergency demands of body

3. The Endocrine System

4. Hormones General characteristics –Specific rates and rhythms of secretion Diurnal, pulsatile and cyclic, and patterns depending on circulating substances –Operate within feedback systems –Affect only target cells with appropriate receptors –The liver inactivates hormones, rendering the hormones more water soluble for renal excretion

5. Regulation of Hormone Release Hormones are released: –In response to an alteration in the cellular environment –To maintain a regulated level of certain substances or other hormones Hormones are regulated by chemical, hormonal, or neural factors Negative feedback

6. Feedback

7. Hormone Transport Hormones are released into the circulatory system by endocrine glands –Water-soluble hormones circulate in free, unbound forms Short-acting response Bind to surface receptors –Lipid-soluble hormones are primarily circulating bound to a carrier Rapid and long-lasting response Bind to plasma membrane

8. Cellular Mechanism of Hormone Action Target cell Up-regulation Down-regulation Hormone effects –Direct effects –Permissive effects

9. Cellular Mechanism of Hormone Action

10. Hormone receptors –Located in the plasma membrane or in the intracellular compartment of the target cell Water-soluble hormones –High molecular weight –Cannot diffuse across the plasma membrane

11. Cellular Mechanism of Hormone Action Lipid-soluble hormones –Easily diffuse across the plasma membrane and bind to cytosolic or nuclear receptors

12. Cellular Mechanism of Hormone Action Water-soluble hormones –First messenger Signal transduction –Second-messenger molecules Calcium Cyclic adenosine monophosphate (cAMP) Cyclic guanosine monophosphate (cGMP) Tyrosine kinase system

13. Cellular Mechanism of Hormone Action Lipid-soluble hormones –Steroid hormones Androgens, estrogens, progestins, glucocorticoids, mineralocorticoids, thyroid hormones, vitamin D, retinoid –Diffuse across the plasma membrane Bind to cytoplasmic or nuclear receptors –Activate DNA transcription and translation

14. Lipid-Soluble Hormones

15. Structure and Function of the Endocrine Glands Hypothalamic-pituitary axis –Hypothalamus –Pituitary gland Anterior pituitary (adenohypophysis) –Pars distalis –Pars tuberalis –Intermedia

16. Structure and Function of the Endocrine Glands –Pituitary gland Posterior pituitary (neurohypophysis) –Median eminence –Pituitary stalk –Pars nervosa

17. The Pituitary Gland

18. Posterior Pituitary Hormones Synthesized with their binding proteins in the supraoptic and paraventricular nuclei of the hypothalamus Secreted by the posterior pituitary –Antidiuretic hormone (ADH) Controls plasma osmolality –Oxytocin Uterine contractions and milk ejection in lactating women

19. Anterior Pituitary Hormones Adrenocorticotropic hormone (ACTH) Melanocyte-stimulating hormone (MSH) Somatotropic hormone Prolactin Thyroid-stimulating hormone

20. Anterior Pituitary Hormones Luteinizing hormone Follicle-stimulating hormone Beta-lipotropin Beta-endorphins

21. Anterior Pituitary Hormones

22. Thyroid and Parathyroid Glands Thyroid gland –Two lobes lie on either side of the trachea –Isthmus –Follicles (follicle cells surrounding colloid) –Parafollicular cells (C cells) Secrete calcitonin –Regulation of thyroid hormone secretion Thyrotropin-releasing hormone and thyroid- stimulating hormone

23. Thyroid and Parathyroid Glands Thyroid hormones –90% T 4 and 10% T 3 –Bound to thyroxine-binding globulin, thyroxine-binding prealbumin, or albumin –Affect growth and maturation of tissues, cell metabolism, heat production, and oxygen consumption

24. Thyroid and Parathyroid Glands Parathyroid glands –Small glands located behind the upper and lower poles of the thyroid gland –Produce parathyroid hormone Regulator of serum calcium Antagonist of calcitonin

25. Thyroid and Parathyroid Glands

27. Endocrine Pancreas The pancreas is both an endocrine and an exocrine gland Houses the islets of Langerhans –Secretion of glucagon and insulin –Cells Alpha—glucagon Beta—insulin Delta—somatostatin and gastrin F cells—pancreatic polypeptide

28. Endocrine Pancreas

29. Insulin –Synthesized from proinsulin –Secretion is promoted by increased blood glucose levels –Facilitates the rate of glucose uptake into the cells of the body –Anabolic hormone Synthesis of proteins, lipids, and nucleic acids –Amylin Peptide hormone co-secreted with insulin

30. Endocrine Pancreas Glucagon –Secretion is promoted by decreased blood glucose levels –Stimulates glycogenolysis, gluconeogenesis, and lipolysis Somatostatin –Possible involvement in regulating alpha- and beta-cell secretions Gastrin and pancreatic peptides

31. Adrenal Glands Adrenal cortex –80% of an adrenal gland’s total weight –Zona glomerulosa –Zona fasciculata –Zona reticularis Adrenal medulla –Innervated by the sympathetic and parasympathetic nervous systems

32. Adrenal Glands

33. Adrenal cortex –Stimulated by adrenocorticotropic hormone (ACTH) –Glucocorticoid hormones Direct effects on carbohydrate metabolism Anti-inflammatory and growth-suppressing effects Influence awareness and sleep habits Most potent naturally occurring glucocorticoid is cortisol

34. Adrenal Glands Adrenal cortex –Mineralocorticoid hormones Affect ion transport by epithelial cells –Increase the activity of the sodium pump of the epithelial cells –Cause sodium retention and potassium and hydrogen loss Most potent naturally occurring mineralocorticoid is aldosterone –Regulated by the renin-angiotensin system

35. Aldosterone

36. Adrenal Glands Adrenal cortex –Adrenal estrogens and androgens Estrogen secretion by the adrenal cortex is minimal The adrenal cortex secretes weak androgens –Androgens are converted by peripheral tissues to stronger androgens such as testosterone

37. Adrenal Glands Adrenal medulla –Chromaffin cells (pheochromocytes) Chromaffin cells secrete the catecholamines epinephrine (majority) and norepinephrine –Release of catecholamines has been characterized as a “fight or flight” response –Catecholamines promote hyperglycemia

38. Neuroendocrine Response to Stress The endocrine system reacts with the nervous system to respond to stressors The stress response also involves the immune system Influenced by corticotropin-releasing hormone from the hypothalamus

39. Tests of Endocrine Function Radioimmunoassay (RIA) Enzyme-linked immunosorbent assay (ELISA) Bioassay

40. Aging and the Endocrine System Thyroid gland –Glandular atrophy, fibrosis, nodularity, and increased inflammatory infiltrates Parathyroid glands –Related to alterations in calcium balance Inadequate intake, malabsorption, or renal changes Adrenal glands –Decreased clearance of cortisol

41. Elsevier items and derived items © 2008 by Mosby, Inc., an affiliate of Elsevier Inc. Some material was previously published. 1.Which of the following is TRUE regarding thyroid hormone and thyroid-stimulating hormone (TSH)? A.Decreased anterior pituitary release of TSH stimulates thyroid hormone secretion B.TSH is secreted in excess when stimulated by T4. C.TSH secretion is regulated by thyrotropin-releasing hormone. D.TSH secretion is controlled by positive feedback.

42. Elsevier items and derived items © 2008 by Mosby, Inc., an affiliate of Elsevier Inc. Some material was previously published. 2.Which of the following is NOT one of the three types of hormone-secreting cells in the pancreas? A.Alpha B.Beta C.Gamma D.Delta