Endocrine System

1. Endocrine System

2. Endocrine System Overview: Purpose, Basic Structures

3. What is the function of the endocrine system? • To coordinate body functions by facilitating communication between cells in response to environmental and cellular signals.

4. Purpose? • Control development and growth (childhood and adolescence) • Regulates blood pressure, heart rate • Responds to danger, stress • Regulates metabolism • Helps fight infection • Control human reproduction

5. What’s a “gland”? • Group of cells that manufacture secretions • 2 types of glandular secretions • Exocrine – deposited into body cavities, surface of skin through ducts • Endocrine – sent directly into bloodstream • Coordinate body functions

6. How do they do this? • Intracellular communication • Endocrine glands: respond to signals from the environment, other cells • Signals vary… • Environmental (gases, gravity, nutrients, sunlight, temp) • Cellular (hormones) originate inside the body

7. Important to note… • Almost any organ can produce endocrine secretions • Endocrine system composed of 10 endocrine glands

8. Endocrine glands

9. Endocrine glands a.k.a. “ductless glands” • Secretions enter blood directly through capillaries • Don’t direct secretions to any particular part of the body… • Yet not every cell of the body responds to these secretions…

10. How does a cell know if it is supposed to respond? • Receptors! • Special surface molecules (often proteins) that permit cell to detect various types of stimuli • Cells with receptors sensitive to endocrine secretions are called target cells

11. Target cells • Genetically programmed to modify their metabolism when they detect a specific endocrine secretion. • So… Only target cells will respond to the particular secretion

12. Review: Answer these questions • What glands comprise the endocrine system? Whatdo they produce? • Once endocrine secretions are released, where are they deposited? How does this differ from exocrine secretions? • Endocrine secretions are what type of signals?

13. Hormone Function

14. Guiding Questions • What is the function of a ligand? • How do hormones work? • What is an effector? • What is the function of carrier proteins?

15. What is the function of a ligand? • Ligand: general name for a group of chemicals that attach to receptors. • Hormones are a type of ligand • For a ligand to propagate a chemical change, it must have the proper shape to fit into the receptor • When bound to the receptor it causes many chemical reactions within the cell.

16. How do hormones work? • Hormones are released from a gland. They bind to a receptor either on the inside or the outside of the target cell depending on the location of the receptor. • Activates one of several chemical reactions in the cell. • Receptors that are on the surface of the cell = surface receptor • Receptors that are located within the cell = internal receptors

17. What is an effector? • The target cell—the cell a hormone attaches to initiate a biological change

18. What is the function of carrier proteins? To bring hormones that use internal receptors to the target cell OR Once inside the cell, to bring hormones to the receptor

19. Endocrine secretions

20. Guiding Questions • How are endocrine glands different from exocrine glands? • How do endocrine secretions “know” where to go once they’re secreted? • How are autocrine secretions different from paracrine secretions? • Do endocrine secretions usually target cells that are close to the point of origin of the secretion or far from it? • What type of feedback loop does the endocrine system “use” to control the body? Give an example of one.

21. How are endocrine glands different from exocrine glands? • Exocrine: secretions are deposited into body cavities or onto the surface of the skin via ducts • Endocrine: secretions are sent directly to the bloodstream

22. How do endocrine secretions “know” where to go once they’re secreted? • Secretions travel to every part of the body, but only target cells (cells with the correct receptor for the secretion) react.

23. How are autocrine secretions different from paracrine secretions? • Autocrine: interact with the cells that created it. Cells control their own activity. They do not travel in the blood • Paracrine: secretions travel short distances to target cells. • Most important function: coordinate cells within an organ. • Pheromones: leave the body and signal the cells of other organisms.

24. Do endocrine secretions usually target cells that are close to the point of origin of the secretion or far from it? • Both—it depends on the function of the secretion.

25. What type of feedback loop does the endocrine system “use” to control the body? Give an example of one. • Negative feedback loop • A signal that inhibits an endocrine gland by preventing further secretion of a particular hormone. • Similar to temperature control in a building

26. Negative feedback continued • Animation • Thyroxine

27. Types of hormones

28. What do hormones do, again? • Signals a cell to alter its metabolism… but must be programmed to do so • Hormones can be many things… • Agonists – chemicals that act as hormones (phytoestrogens from food that act like certain hormones) • Antagonists – chemicals that block the actions of hormones • A.k.a. mimics/hormone disruptors

29. Guiding Questions • What is the function of a hormone? • What is an agonist? What is its function? • What is an antagonist? What is its function? • What are the two types of hormones? What are their functions?

30. 2 types of hormones: • Peptide – biological molecule made of amino acid chains (named for the peptide bond in proteins) • Produced “on-demand” • Signaled by internal/external cues • Lipid – made from existing lipids in body, taken in through diet • Body converts cholesterol to a particular hormone • Can be interconverted, too

31. Peptide hormones • 1  many amino acids (polypeptide) • Effects usually rapid • Often involved in immediate changes in metabolism, but some permanent • Ex. Growth hormone • Bind to surface receptors (can’t enter cell through membrane) • Broken down by enzymes to prevent accumulation in blood • Some taken in, where they bind to internal receptors

32. Lipid hormones • Fluid regulation, sexual reproduction • 2 types: • Hormone-like lipids • Single chain of fatty acids (ex. prostaglandins, a signaling hormone) • Steroids • More complex • Specific signaling • Not water soluble; carried via carrier molecules • Can move across cell membrane easily, interacting w/ DNA • Broken down by enzymes to prevent accumulation • Can cause metabolic problems, cancer if levels too high

33. Two kinds of lipid hormones: Hormone-like Lipids: single chain of fatty acid • Prostaglandins • Produced by any cell • Immune system control and blood pressure regulation Steroids: made from cholesterol molecules

34. The endocrine glands

35. Guiding Questions Part 1 • How many distinct endocrine glands are there? • Which gland is the “master gland?” • Describe the anatomy, and the location, of the pituitary gland. • What are releasers and how do they function? • How is the posterior pituitary controlled? • Where is the pineal gland located, and what hormones does it produce?

36. Guiding Questions, Part 2 • Describe the anatomy of the adrenal gland and name its parts. • Describe the location and the function of the adrenal gland. • Where is the thyroid located? How does it control metabolic rate? • Is the pancreas an endocrine gland and/or an exocrine gland? • Describe the cellular organization of the pancreas. What cells are responsible for the endocrine role of the pancreas? What endocrine secretions do these cells produce, and what is the purpose of those secretions? • Where is the pancreas located?

37. Guiding Questions, Part 3! • Where is the thymus gland? What does it secrete? What does the thymus gland control? • What are gonads? What do they do? • Identify the female gonads, their location, and what they produce. • Identify the male gonads, their location, and what they produce. • Describe the function of testosterone, estrogen, and progesterone.

38. The Endocrine Glands – Pituitary and Pineal “Master endocrine gland” • Its hormones control most of the other endocrine glands • intimately linked to the overall coordination of the body’s organ systems. The pineal gland is responsible for producing melatonin and serotonin.

39. Anterior Pituitary • Controlled by releasing hormones, produced by hypothalamus • Responds to various signals from parts of the body • External and internal • Releasing hormones travel from hypothalamusto anterior pituitary via capillaries

40. Posterior Pituitary • Gets information from nerve cells of the hypothalamus • Carry information from brain directly

41. Pineal Gland • Small structure • Above and behind hypothalamus • Produces melatonin (regulates body rhythms) • Related to day length, mood/depression (SAD) • and serotonin • Involved in appetite, emotions, mood, sleep

42. The Endocrine Glands - Adrenal The adrenal glands are made up of an outer cortex and an inner medulla. The adrenal cortex produces corticosteroids and androgens. The adrenal medulla produces adrenaline and noradrenaline.

43. The Endocrine Glands – Thyroid and Parathyroid The thyroid gland helps control the metabolic rate. The parathyroid gland increases calcium levels in the blood.

44. The Endocrine Glands – Pancreas and Thymus pancreas The pancreas produces hormones and digestive enzymes. The thymus gland produces secretions that stimulate the immune system.

45. The Endocrine Glands - Gonads Gonad: An organ of the reproductive system Testis: The male gonad; produces sperm and testosterone Ovary: The female gonad; produces eggs, estrogen, and progesterone

46. Wellness and illness over the life span

47. Guiding Questions Endocrine: Pathology of the Endocrine System 1. How would one know if the endocrine system is affected by disease? Endocrine: Aging of the Endocrine System 1. What happens to hormones as a person ages? 2. What can people do to counteract the effects of an aging endocrine system?

48. How would one know if the endocrine system is affected by disease? • Disorders result from the overproduction or underproduction of one or more hormones. • Not always a simple answer • A decrease in hormone production might be due to an inability to detect signals, lack of signals, diminished blood flow to the gland, or diseased endocrine cells, or tumors.

49. Diabetes insipidus & diabetes mellitus

50. Graves Disease • Inflammation of thyroid gland due to elevated thyroid hormone production (hyperthyroidism) • Caused by an autoimmune disease. • Results: • Elevated metabolic rate • Feelings of nervousness or tension • Feeling tired throughout the day