Importance of the Endocrine System

1. Importance of the Endocrine System 8.1

2. What is the Endocrine System? • the system of glands that produce endocrine secretions (hormones) that help to control bodily metabolic activity

3. Hormones • Chemical regulators produced by cells in one part of the body that affect cells in another part of the body (“to excite or set into motion”  speed up or slow down processes) • Endocrine hormones: chemicals secreted by endocrine glands directly into the blood. • Nontarget hormones: no specific destination  affects many cells throughout the body. • Classified according to their activation site. • Growth hormone (GH) or somatotropin (STH) regulates development of long bones. • Insulin: regulates blood sugar by increasing the permeability of cells to glucose • Epinephrine (adrenaline): produced in times of stress. • Specific hormones  affect specific cells or target tissues • Parathyroid hormone: regulates calcium levels • Gastrin: stimulates cells of stomach to produce digestive enzymes.

4. Chemical Control Systems • Nervous system + Endocrine System  controls function of organs and tissues. • Nervous system: quick adjustments to environment • Endocrine system: maintain control over a longer duration. • GH and sex hormones: regulate and sustain development for many years.

6. The Hypothalamus • Division between the nervous system and endocrine system is most subtle in the hypothalamus. • Hypothalamus: regulates pituitary gland through nerve stimulation. • Endocrine glands: stimulated by pituitary: secrete chemicals that affect the nerve activity of the hypothalamus.

7. Hormones • Serve as regulators: speed up or slow down certain bodily processes.

8. The Relationship between Chemical Messengers and activity of Organ systems • Mering & Minkowsky: 1889 • Pancreas responsible for regulation of blood sugar? • Removed pancreas from dogs •  weight loss & fatigued (symptoms of diabetes). •  ants gathered in kennels with sick dogs. • Urine of sick dogs contained glucose • Insulin (regulation of blood sugar)  produced by pancreas. • Typical experimental method: gland/organ removed  effects monitored  animal injected with varied amounts chemical extracts from organ  monitored. • Problems: • concentrations of other hormones increase to compensate for disorder. • Extra glands removed (ex. Thyroid & parathyroid) • Hormone concentration varies throughout the day.

9. Radioactive Tracers and the Endocrine system • Radioactive tracers: recent technological advance • Enables scientists to follow messenger chemicals from organ in which they are produced to target cells. • Discern how chemical messengers are broken down into other compounds and removed as wastes.

10. Specificity of Hormones • Hormones are very specific • Cells may have receptors for only one hormone • Different types of cells may have a different number of receptor sites for the same hormone (this all depends on how active the cell is in the process in question).

11. Steroid vs. Protein Hormones • Steroid hormones • Modified cholesterol (_______________) • Composed of complex rings of C, H, and O (solubility?) • Male and female sex hormones • Cortisol (AA  glucose by liver) • Protein hormones • Chains of __________ varying in length. • Soluble in water. • Insulin • GH

12. Steroid Hormones • Capillaries  interstitial fluid  target cells (diffusion!) • Within cytoplasm, SHs combine with receptor molecules. • Hormone-receptor complex (HR complex) moves into nucleus • HR complex attaches to segment of chromatin(?) that has a complimentary shape • HORMONE ACTIVATES A GENE  SPECIFIC PROTEIN IS SYNTHESIZED.

13. THE DIAGRAM IN THE TEXTBOOK IS CONFUSING/MISLEADING. ACCORDING TO THE FORMER INFORMATION, HOW WOULD YOU DEPICT THE ACTION OF STEROID HORMONES?

14. Protein Hormones • Capillaries  interstitial fluid  cell membrane • Protein hormones (PHs) combine with receptors on the cell membrane. • PH + receptor  activates production of enzyme which causes cell to convert ATP to AMP. • AMP: CYCLIC ADENOSINE MONOPHOSPHATE: secondary chemical messenger that directs the synthesis of protein by ribosomes • Activates enzymes in cytoplasm to carry out NORMAL functions.

16. Main ideas so far... • The two main types of hormones are ______________and ______________ hormones. • Steroid hormones: • Steroids are a type of ___________. They can diffuse through the __________________. • While in the cytoplasm, a SH may combine with a _______________ molecule. This complex moves into the _____________ where it attaches to ________ which will then activates a gene and consequently produce a specific ___________________. • Protein hormones: • Proteins are made up of ___________. Many of these may be polar. Therefore, they cannot easily diffuse through the ______________. • PHs combine with receptor sites on the target cell’s ________________. • PH + receptor site  reaction inside of the cell. • ATP  _____________ • AMP  activates ___________________ to carry out normal functions.

17. Example of a Protein Hormone TSH = thyroid-stimulating hormone • Attaches to receptor sites in the cells of the thyroid gland  AMP is produced within cells  specific enzymes are activated  thyroxineis produced  increases metabolism & growth regulated Thyroxine: increases rate of metabolism and regulates growth.

18. The Pituitary Gland: The Master Gland (1) • Controls most other endocrine glands. • Connected to the hypothalamus • Pituitary + hypothalamus: interconnected. • Pituitary gland: produces and stores hormones. • Hypothalamus: stimulates the release of hormones by the pituitary gland by way of nerves.

19. The Pituitary Gland: The Master Gland (2) • Two lobes: • Posterior: • stores and releases hormones like ADH and oxytocin (oxytocin uterine contractions during labour). • both produced by the hypothalamus. • Posterior lobe does not produce hormones  hormones sent to pituitary via. specialized nerve cells. • Anterior: • Produces its own hormones. • Rich with nerves from hypothalamus  regulates release of hormones from anterior pituitary. • Hypothalamus releasing factors: inhibit secretion of hormones from anterior lobe • Dopamine: inhibits secretion of prolactin (stimulates milk production) • Somatostatin: inhibits secretion of somatotropin (growth of long bones)

21. Pituitary Hormones

22. Understanding Concepts

23. 8.2 – Hormones that Affect Blood Sugar • Pancreas • Contains two types of cells • 1) produces digestive enzymes • 2) produces hormones • Located in structures called the islets of Langerhans • Thousands of islets containing thousands of cells each responsible for production of insulin and glucagon. • Alpha and beta cells • INSULIN (beta cells): secreted with blood sugar levels are high • GLUCAGON (alpha cells): promotes conversion of glycogen to glucose when blood sugar levels are low

24. Insulin • Produced in beta cells • After a meal, blood sugar levels increase • Appropriate amt. Of insulin released • Insulin causes cells of muscles, liver, and other organs to become permeable to glucose • Liver: glucose converted to glycogen: _____________________________________. •  therefore, blood sugar levels _______________.

25. Glucagon • Produced by alpha cells • Periods of fasting  blood sugar levels are low  glucagon released • Promotes conversion of glycogen to glucose (liver) which is released into blood. •  therefore, blood sugar levels ______________.

27. Diabetes(1) • Chronic disease • No cure • Affects more than 2 million Canadians • Overall: insufficient production or use of insulin. • Can cause blindness, kidney failure, nerve damage, and nontraumatic limb amputation.

28. How Diabetes ‘works’ • Without insulin, blood sugar levels __________ rapidly after meals. • Hyperglycemia: high blood sugar. • Kidneys unable to reabsorb all blood glucose: glucose in urine. • High concentrations of glucose in nephrons draw water out of blood/interstitial fluid  unusually large volumes of urine, often thirsty. • Low energy levels: cells are not permeable to glucose. • Cells turn to other sources of energy: fats and proteins  acetone (intermediate of excessive fat metabolism) may build up.

29. Types of Diabetes Mellitus • Type 1 • Early degredation of beta cells in islets of Langerhans • Diagnosed in childhood • About10% of cases • Type 2 • Decrease production/ineffective use of insulin • Diagnosed in adulthood  controlled by diet, exercise, oral drugs. • About 90% • Type 3 • Gestational diabetes: temporary • Occurs in 2-4% of pregnancies; increase of diabetes in mother and child.

30. Independent Reading • Read sections “Research in Canada...” and “Frontiers of Technology”, starting on page 379. • Answer the following questions in your notebook: • What problem does extracting hormones from the pancreas present? • Briefly describe the procedure and results from Banting and Best’s experiments. • What is the second leading cause of blindness in Canada? What are some other side effects of this disease? • What could possibly reverse the effects of diabetes? What is the main barrier keeping this medical procedure from occuring? • Briefly describe the Edmonton Protocol. Why is the liver used? • What is the challenge with the Edmonton Protocol? What is it that is currently providing insulin-producing cells?

31. Adrenal Glands • Located above each kidney. • 2 glands encased in one shell • Adrenal medulla: core of adrenal gland • Produces epinephrine and norepinephrine • Controlled by nervous system • Adrenal Cortex • Hormone regulated

32. Epinephrine & Norepinephrine • Epinephrine: also known as adrenaline. • Norepinephrine: also known as noradrenaline. • Both released from adrenal medulla into blood in times of stress. • Glycogen converted to glucose  blood sugar rises • Greater energy reserve available right away. • Increase of heart rate, breathing rate, and cell metabolism. • Blood vessels dialate, iris of eye dilates.

33. Adrenal Cortex • Produces glucocorticoids: three different TYPES of hormones • Designed to help body meet demands of stress. • Cortisol (most important): • increases levels of amino acids in blood in attempt to help body recover from stress. • AAs Converted to glucose by liver, raising blood sugar. • AAs not converted: available for protein synthesis  repair damaged cells. • Fats and adipose tissue broken down into FAs  source of energy

34. Long-term stress Response • Hypothalus sends a releasing hormone to the anterior lobe of the pituitary • Corticotropin (adrenocorticotropic hormone, ACTH) released  adrenal cortex  secretes hormones like cortisol  target cells in liver and muscles  as cortisol levels rise, cells within hypothalamus and pituitary decrease production of regulatory hormones  cortisol decreases.

35. Short-term stress Response • Regulated by adrenal medulla  secretes epinephrine & norepinephrine.

36. Aldosterone (again) • A mineralocorticoid. • Increases sodium retention and water reabsorption by kidneys  maintain body fluid levels.

39. Seatwork/Homework • Page 383 #1-7

40. 8.3 – Hormones that Affect Metabolism • What is metabolism, again? • Three glands which affect metabolism are: • Thyroid gland • Produces three major hormones • Parathyroid glands • Produces the parathyroid hormone • Anterior pituitary gland • Produces the growth hormone along with many other regulatory hormones

41. Thyroid Gland • Located at the base of the neck, in front of the trachea • Two important thyroid hormones: • Thyroxine (T4) • 65% of thyroid secretions • Triiodothyronine (T3)

43. Metabolic Rate and YOU • Have you ever wondered why some people seem to consistently eat a lot of food, and not gain any weight? • This is partially due to the hormone thyroxine.

44. High levels of Thyroxine • High levels of thyroxine means increased metabolic rate • 60% of the energy of glucose metabolized is released as heat • People with a ‘high’ metabolic rate usually feel warm. • 40% is transferred to ATP  not to fat. • These people do not tend to gain weight.

45. Low levels of Thyroxine • Those with low levels of thyroxine do not tend to break down sugars very quickly. • Excess blood sugar is eventually converted to liver and muscle glycogen. • Once glycogen stores are filled, excess sugar is converted into fat.

46. Important note: Not all weight gain is due to low thyroid secretions. In many cases, it reflects a poor diet.

47. Control of Thyroid Hormones (Thyroxine) • Accomplished through negative feedback • If metabolic rate decreases  receptors in hypothalamus  nerve cells secrete thyroid-releasing hormone (TRH)  TSH released from pituitary  carried through blood to thyroid gland  release of thyroxine • THYROXINE: increases metabolism by stimulating increased sugar utilization by body cells. • High levels of thyroxin inhibits release of TRH from hypothalamus  negative feedback!

48. Thyroid Disorders • Iodine: important component of thyroid hormones. • Normal component in the blood • Actively transported from blood to follicle cells of the thyroid. • Goiter: inadequate amounts of iodine in diet. • Without iodine, thyroid production and secretion of thyroxine drops. • What effect would this have on the production of TSH: ______________________. Thyroid stimulated more and more  cells develop  thyroid enlarges.

49. In many countries, iodine is added to table salt to prevent this condition.