Homeostasis and Endocrine Systems

1. Homeostasis and Endocrine Systems Hormonal Control and Homeostasis

2. Endocrine vs. Exocrine

3. Endocrine System

4. Homeostasis The maintenance of internal environment between limits, including blood pH, carbon dioxide concentration, blood glucose concentration, body temperature, and water balance Negative feedback is generally the mechanism of action

5. Temperature Regulation If too hot, move blood into capillaries and sweat so that the energy to evaporate the water will come from the body heat. If too cold, increase metabolic rate (T4 production) from the Hypothalamus, shiver, decrease blood flow to skin.

8. Activities in the Cell • Quick signaling is provided by the nervous system. • Slower with chemical signals is provided by the endocrine system. • Endocrine vs Exocrine

9. Chemical Signals Intracellular (signal transduction) Cell to Cell Tissue to Tissue Organ to Organ Organism to Organism

10. Growth Factors • Peptides and Proteins that regulate the growth of developing tissues. • Must be in the extracellular environment for certain cell types to grow and develop normally.

11. Prostaglandins • Modified fatty acids released into interstitial tissues that function as local regulators. • Released by placenta and cause increased contractions. • Also cause local cramps the first few days of a period

12. How Hormones work • Specific receptors determine action of target cells. • Activation of a signal transduction pathway leads to cellular response. Know these two modes • Plasma membrane protein binding • insulin • Steroid hormones (they are lipids) • enter cells and bind with intracellular receptors.

13. Signal Transduction

14. More Signal Transduction (Second Messenger Hypothesis)

15. Gonadal steroids • Estrogens • Estradiol • Progestins • Progesterone • Androgens • Testosterone

16. Lipid based hormone

17. Hypothalamus and Pituitary

18. Brain

19. Vertebrate Endocrine System Tropic hormones act on other endocrine glands. Hypothalamus and Pituitary integrate many functions of the vertebrate endocrine system.

20. Types of Hormones • Steroids • Testosterone • Peptides • Insulin • Tyrosine Derivatives • Thyroixin

21. Pituitary Functions Anterior Pituitary Hormones Posterior Pituitary Hormones

22. Hypothalamus and Pituitary

23. Hypothalamus • Receives signals from the body. • Initiates endocrine signals that respond to environmental conditions. • Contains two sets of neurosecretory cells whose secretions are stored in or regulate acitivity in the pituitary gland. • GHRH • GnRH • TRH • Oxytocin • ADH

24. Posterior Pituitary • Neurosecretory cells of hypthalamus release hormones to the posterior Pituitary to be stored and released into blood stream. • Oxytocin induces uterine muscle contractions and cause the mammary glands to eject milk during nursing • ADH acts on the kidneys to increase water retention, which decreases urine volume.

25. Kidney

27. ADH Function

28. ADH Osmoreceptors in the hypothalamus monitor blood osmolarity. When blood has high osmolarity the osmoreceptors shrink(makes person thirsty). The hypothalamus and neurosecretory cells release ADH. Reaches the cells and activates a signal transduction pathway making cells permeable to water. Water moves into the capillaries and back into blood.

29. Anterior Pituitary • Tropic Hormones – Cause another gland to release hormones. • TSH, ACTH, FSH, LH • Growth Hormone (somatotropin)– protein hormone that affects a large variety of tissues. • promotes the production of growth factors.

30. Anterior Pituitary Continued • Prolactin (PRL) – protein hormone • stimulates mammary gland development and milk synthesis • Regulation of fat metabolism and reproduction in birds. • Delays metamorphosis and larval growth hormone in amphibians. • Salt and water balance in freshwater fish.

31. Regulation of Breast Feeding

32. Milk Ejection

33. Anterior Pituitary Continued • Follicle Stimulating Hormone • In males it is necessary for spermatogenesis • In females, it stimulates ovarian follicle growth. • Lutenizing Hormone- Stimulates ovulation and corpus luteum formation in females and spermatogenesis in males. • Thyroid Stimulating Hormone- Stimulates Thyroid gland to release two hormones

34. Anterior Pituitary Continued • The last hormones are produced as one and are cleaved into three • Adrenocorticotropic hormone (ACTH) – Stimulates Adrenal cortex to produce and secrete steroid hormones. • Melanocyte Stimulating hormone- Regulates the activity of pigment containing skin cells in some vertebrates. • Endorphins- inhibit pain receptors.

35. Thyroid Gland

36. Thyroid Gland • Produces two modified amino acid (Tyrosine) hormones • T3 or Triiodothyronine • T4 or Tetraiodothyronine or Thyroxine • Both have same effect but T3 is more active in mammals. • Normal blood pressure, heart rate, muscle tone, digestion, and reproduction • Increase the rate of oxygen consumption and cellular metabolism. • Also secretes Calcitonin- Lowers blood calcium levels

37. Thyroid Gland Hyperthyroidism- Excessive secretion of thyroid hormones. High body temp, sweating, weight loss, irritability, high blood pressure. Hypothyroidism- low secretion. cretinism in infants, weight gain, lethargy, cold intolerance. Goiter- enlarged thyroid. Iodine deficiency.

38. Hyperthyroidism, Goiter

39. Regulation of Thyroid • TRH is released from Hypo • TSH is released from Anterior Pit. • Binds with receptors on Thyroid cells. Activates cAMP which stimulates the release of T3 and T4. • High T3 and T4 inhibit the release of TRH and TSH

40. Action of Thyroid Hormones

41. Thyroid and Parathyroid… Calcium Balance

42. Pancreatic Endocrine Function • Endocrine cells in solid balls of cells called Islets of Langerhans. • Alpha cells secrete Glucagon • Beta cells secrete Insulin • Normal blood glucose 90 mg/dL • Diabetes mellitus type 1. Autoimmune disorder. Usually onset in childhood. • Type 2 D. mellitus. Usually onset at 40 and generally is lack of senativity to insulin at receptors.

44. Sex Endocrine Hormone Regulation