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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 brain hormone (BH), 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. Major Endocrine Organs

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

  15. 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

  16. hypothalamus anterior pituitary posterior pituitary Pituitary Gland

  17. Posterior Pituitary Hypothalamus Posterior Pituitary Anterior Pituitary

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

  19. Anterior Pituitary Hypothalamus Posterior Pituitary Anterior Pituitary

  20. 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)

  21. 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.

  22. strenuous exercise GH Levels sleep awake

  23. 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.

  24. 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.

  25. Thyroid Gland larynx thyroid trachea

  26. Thyroid Follicles

  27. 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

  28. Thyroid Hormone Regulation

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

  30. parathyroid glands thyroid esophagus trachea Parathyroid Glands

  31. 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

  32. PTH Effects

  33. Pancreas

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

  35. Islets of Langerhan

  36. 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

  37. 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

  38. Regulation of Blood Sugar Levels

  39. Diabetes Melitus

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

  41. adrenal cortex adrenal medulla Adrenal Glands

  42. Hormones of the Adrenal Medulla • Adrenalin (epinephrine): converts glycogen to glucose in liver • Noradrenalin (norepinephrine): increases blood pressure • (sympathetic nervous system) • Corticosteroids: glucose levels)

  43. Hormones of the Adrenal Cortex • Glucocorticoids- cortisol • Decrease protein synthesis • Increase release and use of fatty acids • Stimulates the liver to produce glucose from non carb’s • Mineralcorticoids- aldosterone • Stimulates cells in kidney to reabsorb Na+ from filtrate • Increases water reabsorption in kidneys • Increases blood pressure • Sex Steroids- small amts (androgens) • Onset of puberty • Sex drive

  44. Cushing’s Syndrome Hypersecretion of cortisone; may be caused by an ACTH releasing tumor in pituitary Symptoms: trunkal obesity and moon face, emotional instability Treatment: removal of adrenal gland and hormone replacement

  45. Addison’s Disease Hyposecretion of glucocorticoids and mineral corticoids; Symptoms- wt loss, low levels of plasma glucose and Na+ levels, high levels of K+ Treatment- corticosteroid replacement therapy

  46. Thymus Located anterior to the heart Produces- thymopoetin and thymosin helps direct maturation and specialization of T-lymphocytes (immunity)

  47. Gonads Ovaries- produce estrogen and progesteroneresponsible for maturation of the reproductive organs and 2ndary sex characteristics in girls at puberty

  48. Female Reproductive System

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