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Chapter 23

Chapter 23. Adrenal glands Thyroid hormones Growth hormone Tissue and bone growth Calcium balance. Review of Endocrine Principles. Hypothalamic-pituitary control system Several hormones controlled by hypothalamic and anterior pituitary trophic hormones Feedback patterns

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Chapter 23

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  1. Chapter 23 • Adrenal glands • Thyroid hormones • Growth hormone • Tissue and bone growth • Calcium balance

  2. Review of Endocrine Principles • Hypothalamic-pituitary control system • Several hormones controlled by hypothalamic and anterior pituitary trophic hormones • Feedback patterns • Negative feedback: • Simple Pathway-Blood glucose level decreasing shuts off insulin secretion • Complex Pathway-use the hypothalamic-pituitary control system, where the feedback signal may be the hormone itself • Hormone receptors • May be on surface or inside the cell • Cellular responses • Target cells respond by altering existing proteins or making new proteins • Magnitude of target cell response • Depends on number of receptors and amount of active hormone • Endocrine pathologies • Excess hormone secretion • Inadequate hormone secretion • Abnormal target cell response to the hormone

  3. Adrenal Glands Structure and function of the adrenal gland Figure 23-1a

  4. Adrenal Glucocorticoids Figure 23-1b

  5. Adrenal Glands Figure 23-1c

  6. Adrenal Cortex Secretes Steroid Hormones • Aldosterone (Mineralcorticoid) • Glucocorticoids • Cortisol • Sex Hormones

  7. Adrenal Glucocorticoids Synthesis pathways for steroid hormones Figure 23-2

  8. Cortisol The HPA pathway for the control of cortisol secretion Corticotropin Releasing Hormone Adrenocorticotropic Hormone Figure 23-3

  9. Circadian Rhythm of Cortisol Secretion Figure 23-4

  10. Cortisol

  11. Cortisol • Promotes gluconeogenesis • Causes breakdown of skeletal muscle proteins • Enhances lipolysis • Suppresses the immune system • Causes negative calcium balance • Influences brain function

  12. Cortisol: Therapeutic Drug • Suppresses the immune system • Inhibits the inflammatory response • Used to treat • Bee stings, poison ivy, and pollen allergies • Prevents rejection of transplanted organs

  13. Hypercortisolism Hypercortisolism: Excess cortisol in the body Cushings Syndrome: Hormonal disorder caused by prolonged exposure to excess cortisol (including iatrogenic). • Signs and Symptoms • Hyperglycemia • Muscle protein breakdown • Excess deposits of extra fat in trunk and face • Thin arms and legs • Thin skin and bruising Three causes of hypercortisolism: • Adrenal tumor that autonomously secretes cortisol (Primary Hypercortisolism) • Pituitary tumor that autonomously secretes ACTH (Secondary Hypercortisolism or Cushing’s Disease) • Iatrogenic hypercortisolism

  14. Hypercortisolism Figure 23-5

  15. Hypocortisolism • Less common than Cushing’s syndrome • Addison’s disease • Hyposecretion of all adrenal steroid hormones • Autoimmune destruction of adrenal cortex

  16. Thyroid: Structure Figure 23-7a

  17. Thyroid: Structure Figure 23-7b

  18. Thyroid Thyroid hormones are made from iodine and tyrosine Figure 23-8

  19. Thyroid

  20. Hyperthyroidism • Increases oxygen consumption and metabolic heat production • Increase protein catabolism and may cause muscle weakness • Hyperexcitable reflexes and psychological disturbances • Influence -adrenergic receptors in the heart

  21. Hypothyroidism • Slow metabolic rate and oxygen consumption • Decreases protein synthesis • Slowed reflexes, slow speech and thought processes, and feelings of fatigue • Cretinism in infants • Bradycardia

  22. Pathway of Thyroid Hormone Control Figure 23-12

  23. Thyroid A man with goiter due to excessive TSH stimulation Figure 23-13

  24. Thyroid Goiter can occur in both hyperthyroidism and hypothyroidism Figure 23-14a

  25. Thyroid Figure 23-14b

  26. Normal Growth • Growth hormone and other hormones • An adequate diet • Absence of stress • Genetics

  27. Pathway of Growth Hormone Control Figure 23-16

  28. Growth Hormone

  29. Growth Hormone • Severe GH deficiency leads to dwarfism • Oversecretion of GH in children leads to giantism • Oversecretion of GH in adults leads to acromegaly

  30. Three Individuals with Acromegaly Figure 23-17

  31. Bone growth Epiphysis is the end of a long bone. Diaphysis is the shaft of a long bone. Bone gr owth Compact bone Dividing chondrocytes add length to bone. Epiphyseal plate is the site of bone growth. Chondrocyte Direction of growth Chondrocytes produce cartilage. Old chondrocytes disintegrate. Cartilage Osteoblasts lay down bone on top of cartilage. Diaphysis Newly calcified bone Osteoblast Linear growth of long bones takes place at the epiphyseal plates Figure 23-19

  32. Bone growth Epiphysis is the end of a long bone. Diaphysis is the shaft of a long bone. Epiphyseal plate is the site of bone growth. Diaphysis Figure 23-19 (1 of 5)

  33. Bone growth Epiphysis is the end of a long bone. Diaphysis is the shaft of a long bone. Compact bone Dividing chondrocytes add length to bone. Epiphyseal plate is the site of bone growth. Chondrocyte Diaphysis Figure 23-19 (2 of 5)

  34. Bone growth Epiphysis is the end of a long bone. Diaphysis is the shaft of a long bone. Compact bone Dividing chondrocytes add length to bone. Epiphyseal plate is the site of bone growth. Chondrocyte Chondrocytes produce cartilage. Cartilage Diaphysis Figure 23-19 (3 of 5)

  35. Bone growth Epiphysis is the end of a long bone. Diaphysis is the shaft of a long bone. Compact bone Dividing chondrocytes add length to bone. Epiphyseal plate is the site of bone growth. Chondrocyte Chondrocytes produce cartilage. Old chondrocytes disintegrate. Cartilage Diaphysis Figure 23-19 (4 of 5)

  36. Bone growth Epiphysis is the end of a long bone. Diaphysis is the shaft of a long bone. Bone gr owth Compact bone Dividing chondrocytes add length to bone. Epiphyseal plate is the site of bone growth. Chondrocyte Direction of growth Chondrocytes produce cartilage. Old chondrocytes disintegrate. Cartilage Osteoblasts lay down bone on top of cartilage. Diaphysis Newly calcified bone Osteoblast Figure 23-19 (5 of 5)

  37. Calcium Balance

  38. Calcium • Important signal molecule • Part of intercellular cement that holds cells together at tight junction • Cofactor in the coagulation cascade • Affects the excitability of neurons

  39. Calcium Balance in the Body Small intestine Dietary calcium Calcium in feces Ca2+ Calcitrol (PTH, prolactin) Some calcium is secreted into the small intestine. ECF Bone Kidney Passive filtration Calcitonin [Ca2+] Ca2+ in kidney tubules Ca2+ 2.5 mM PTH PTH Calcitriol Calcitonin Cortisol Electrochemical gradient Active transport Cells [free Ca2+] 0.001 mM KEY Ca2+ in urine PTH = parathyroid hormone Figure 23-20

  40. Calcium Balance in the Body ECF [Ca2+] 2.5 mM KEY PTH = parathyroid hormone Figure 23-20 (1 of 5)

  41. Calcium Balance in the Body ECF [Ca2+] 2.5 mM Electrochemical gradient Active transport Cells [free Ca2+] 0.001 mM KEY PTH = parathyroid hormone Figure 23-20 (2 of 5)

  42. Calcium Balance in the Body ECF Bone Calcitonin [Ca2+] Ca2+ 2.5 mM PTH Calcitriol Cortisol Electrochemical gradient Active transport Cells [free Ca2+] 0.001 mM KEY PTH = parathyroid hormone Figure 23-20 (3 of 5)

  43. Calcium Balance in the Body Small intestine Dietary calcium Ca2+ Calcitrol (PTH, prolactin) ECF Bone Calcitonin [Ca2+] Ca2+ 2.5 mM PTH Calcitriol Cortisol Electrochemical gradient Active transport Cells [free Ca2+] 0.001 mM KEY PTH = parathyroid hormone Figure 23-20 (4 of 5)

  44. Calcium Balance in the Body Small intestine Dietary calcium Calcium in feces Ca2+ Calcitrol (PTH, prolactin) Some calcium is secreted into the small intestine. ECF Bone Kidney Passive filtration Calcitonin [Ca2+] Ca2+ in kidney tubules Ca2+ 2.5 mM PTH PTH Vitamin D Calcitonin Cortisol Electrochemical gradient Active transport Cells [free Ca2+] 0.001 mM KEY Ca2+ in urine PTH = parathyroid hormone Total body calcium = intake  output Figure 23-20 (5 of 5)

  45. Calcium Balance Osteoclasts are responsible for bone resorption Figure 23-21

  46. Calcium Balance • Parathyroid hormone • Mobilizes calcium from bone • Enhances renal reabsorption • Indirectly increases intestinal absorption • Vitamin D (Calcitriol) • Calcitonin (from Thyroid)

  47. Calcium Balance: Parathyroid Glands Figure 23-22

  48. Calcium Balance

  49. Endocrine Control of Calcium Balance Figure 23-23

  50. Calcitonin

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