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Chapter 45

Chapter 45. Chemical Signals in Animals. Hormones. Hormones are chemical signals. The endocrine system consists of: Endocrine cells which are hormone-secreting cells and Endocrine glands which are hormone-secreting organs. Specific target cells respond to specific hormones.

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Chapter 45

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  1. Chapter 45 Chemical Signals in Animals

  2. Hormones • Hormones are chemical signals. • The endocrine system consists of: • Endocrine cells which are hormone-secreting cells and • Endocrine glands which are hormone-secreting organs. • Specific target cells respond to specific hormones.

  3. Primary Function of Hormones • Homeostasis • Growth and Development • Reproduction • Energy Metabolism • Behavior

  4. stimulates glucose release from liver glucagon from pancreas stimulates inhibits blood glucose high Negative Feedback Loop blood glucose low

  5. Biological Cycles

  6. hormones endocrine cell receptor protein target cell Mechanism of Action on Target Cells response

  7. hormones endocrine cell intracellular receptor target cell Mechanism of Action on Target Cells response

  8. Tropic vs Nontropic Hormones Tropic hormones- stimulate the production and secretion of hormones by other endocrine glands; ex. TSH Nontropic hormones- stimulates cellular growth, metabolism, or other functions; ex. thyroxine

  9. Invertebrate nervous systems clearly illustrate endocrine and nervous system interactions • Invertebrates have a wide variety of hormones that are involved in the regulation of homeostasis.

  10. An example from hydra: • One hormone stimulate asexual reproduction. • Another hormone prevents sexual reproduction. • An example from a mollusk: • The hormone that regulates egg laying also inhibits feeding and locomotion.

  11. Arthropods have extensive endocrine systems regulating molting in insects and crustaceans. • The regulation of molting in insects. • Ecdysone also promotes the development of adult features. • Neurosecretory cells in the brain produce Prothoracicotropic hormone (PTTH), which regulates the secretion of ecdysone. • Juvenile hormone (JH) promotes the retention of larval characteristics.

  12. Different signal-transduction pathways in different cells can lead to different responses to the same signal.

  13. Frog Metamorphosis thyroxin

  14. Major Endocrine Organs Major endocrine glands: Hypothalamus Pineal gland Fig. 45-10 Pituitary gland Organs containing endocrine cells: Thyroid gland Thymus Parathyroid glands Heart Liver Adrenal glands Stomach Pancreas Kidney Testes Small intestine Kidney Ovaries

  15. pineal gland hypothalamus pituitary gland Endocrine Organs of the Brain

  16. Pineal Gland Produces melatonin (synthesized from seratonin, a derivative of tryptophan) • Secreted directly in CSF to blood • High levels at night make us sleepy; low level during day • Pineal gland is stimulated by darkness and inhibited by light • Function in regulating circadian rhythms (sleep, body temp, appetite)  biological clock

  17. hypothalamus anterior pituitary posterior pituitary Pituitary Gland

  18. Posterior Pituitary Hypothalamus Posterior Pituitary Anterior Pituitary

  19. Hormones of the Posterior Pituitary Antidiuretic Hormone (ADH) Oxytocin (+ feedback)

  20. Anterior Pituitary Hypothalamus Posterior Pituitary Anterior Pituitary

  21. Hormones of the Anterior Pituitary • Growth Hormone (GH) • Dwarfism • Gigantism & Acromegaly • Thyroid Stimulating Hormone (TSH) • Adrenocorticotropic Hormone (ACTH) • Gonadotropins (FSH, ICSH, LH) • Prolactin (PRL) • Melanocyte-stimulating Hormone (MSH)

  22. Growth Hormone (GH) • Acts on the liver, stimulating it to release several polypeptide hormones. • Stimulates amino acid uptake and protein synthesis in target cells. • Ultimately stimulates cell growth (cell size and number), especially in muscle and bone. • Also stimulates fat breakdown.

  23. strenuous exercise GH Levels sleep awake

  24. Dwarfism hyposecretion of GH Little People Big World Kenadie - worlds smallest girl due to primordial dwarfism

  25. Gigantism hypersecretion of GH Bao Xishun, a 7ft 8.95in herdsman from Inner Mongolia

  26. Acromegaly hypersecretion of GH 7 ft 1 ¼ inches

  27. Thyroid-Stimulating Hormone (TSH) • Acts on the thyroid gland, stimulating it to release T3 & T4 • These thyroid hormones increase glucose catabolism and body heat production. • Negative feedback mechanism involved in regulating levels.

  28. Adrenocorticotropic Hormone (ACTH) • Acts on the adrenal cortex, stimulating it to secrete glucocorticoids (e.g., cortisol). • Glucocorticoids promote the synthesis of glucose from noncarbohydrate sources such as amino acids, and fatty acids • Negative feedback mechanism involved in regulating levels.

  29. Thyroid Gland larynx thyroid trachea

  30. Thyroid Follicles

  31. Thyroid Hormones Thyroid gland selectively uptakes iodine to produce T3 & T4 • Thyroxine (T4) • Triiodothyronine (T3) • Both control metabolic rate and cellular oxidation • Calcitonin (from parafolicular cells)- lowers blood CA ++ levels and causes CA++ reabsorption in bone

  32. Thyroid Hormone Regulation

  33. Thyroid Disorders • Hyperthyroidism (Grave’s, Goiter) • Hypothyroidism (Cretinism, Myxedima)

  34. Goiter Lack of iodine in diet hyposecretion of T3 & T4

  35. Cretinism hyposecretion of T3 & T4

  36. Myxedemahyposecretion of T3 & T4 After thyroid treatment myxedema

  37. Exophthalmos-hyperthyroidism

  38. Parathyroid Glands

  39. Parathyroid Hormone (PTH) • PTH release: • stimulates osteoclasts • enhances reabsorption of Ca++ by kidneys • increases absorption of Ca++ by intestinal mucosal cells • Hyperparathyroidism- too much Ca++ drawn out of bone; could be due to tumor • Hypoparathyroidism- most often follow parathyroid gland trauma or after removal of thyroid--- tetany, muscle twitches, convulsions; if untreatedrespiratory paralysis and death

  40. PTH Effects

  41. Pancreas

  42. Pancreas • Regulates glucose uptake by cells • Controlled via negative feedback: insulin & glucagon • Blood sugar level: 90 mg/mL

  43. Islets of Langerhan

  44. Insulin • Produced by the  cells of the Islets of Langerhan • Catalyze oxidation of glucose for ATP production • Lowers blood glucose levels by promoting transport of glucose into cells. • Stimulates glucose uptake by the liver and muscle cells. • Stimulates glycogen synthesis in the liver and muscle cells. • Also stimulates amino acid uptake and protein synthesis of muscle tissue

  45. Glucagon • Produced by the  cells of the Islets of Langerhans • Stimulates change of glycogen to glucose in the liver. • Synthesis of glucose from lactic acid and non carbohydrate molecules such as fatty acids and amino acids • Causes  in blood glucose concentration hypoglycemic- low blood sugar; deficient in glucagon

  46. Regulation of Blood Sugar Levels

  47. Diabetes Melitus

  48. Type I Diabeteshyposecretion of insulin insulin dependant juvenile onsetType II Diabetes late onset (adult) insensitivity of cells to insulin manage by exercise & diet

  49. adrenal cortex adrenal medulla Adrenal Glands

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