The Endocrine System

1. Mr. Wright 2011 Chapter 11: The Endocrine System

2. Section 11.1 Introduction

3. The Endocrine System • The body has two systems designed for communication: • The Nervous System • The Endocrine System • Allows the body to change to different situations.

4. The Endocrine System • Made up of glands. • Glands secrete hormones. • Hormones enter the bloodstream and are carried to specific target cells.

5. Local Hormones • Some hormones never enter the bloodstream… they stay in the same area and are called local hormones. • Paracrine – affect neighboring cells • Autocrine – affect the secreting cells themselves.

6. Exocrine Glands • Exocrine glands secrete things outside the body. • Example: Sweat

7. Section 11.2 General Characteristics

8. Comparing Nervous & Endocrine • Involved in communication. • Releases neurotransmitters into synapses. • Very precise. • Very brief. • Involved in communication. • Releases hormones into bloodstream • Very precise. • Can be brief or very long. Nervous System Endocrine System

9. Things the Endocrine System Controls… • The endocrine system regulates many metabolic processes. • Rates of chemical reactions. • Transport across membranes. • Regulate water and electrolyte balances. • Reproduction • Development • Growth

10. Glands of the Endocrine System

11. Section 11.3 Hormone Action

12. Hormones • There are 3 main types of hormones: • Steroids • Nonsteroids • Prostalandins

13. Steroid Hormones • Steroid hormones are made or rings of carbon and hydrogen atoms. • They are insoluble in water, but are soluble in lipids (fats) like cell membranes. • Thus, they can enter and exit cells easily.

14. Nonsteroid Hormones • Nonsteroid hormones cannot enter cells. • Instead, they combine with receptors in the cell membrane.

15. Prostaglandins • Prostaglandins are special lipids synthesized from fatty acids in the cell membrane. • Produced in the liver, kidneys, heart, lungs, brain, and several endocrine glands.

16. Prostaglandins • Produce many diverse effects. • Relax/Contract smooth (involuntary) muscles. • Stop production of stomach acid. • Influence movements of salt and water in the kidney. • Regulates blood pressure. • Stimulates other hormones.

17. Section 11.4 Control of Hormonal Secretions

18. Hormonal Secretions • As hormone levels increase in the blood, hormone secretion decreases. • The more there is, the less we need. • The opposite of this statement is true as well.

19. Hormonal Secretions • Hormonal secretion is controlled by negative feedback. • Negative feedback – the mechanism is controlled by an imbalance that corrects it.

20. Examples of Negative Feedback • The hypothalamus stimulates the pituitary gland to secrete hormones. • The pituitary gland secrets hormones which stimulate the ovaries to secrete hormones needed for puberty. • If the ovary hormone levels in the blood are too high, the hypothalamus stops stimulation.

21. Examples of Negative Feedback • When blood sugar levels are high, the pancreas secretes insulin. • Blood sugar levels decrease. • Once blood sugar levels are low enough, pancreas stops secreting insulin.

22. Conclusion • As a result of negative feedback, hormone levels in the blood remain relatively stable, with only slight changes.

23. Section 11.5 The Pituitary Gland

24. Structure • The pituitary gland is found hanging beneath the brain. • Very small. • Attached to the brain by a small stalk called the infundibulum. • 2 halves: • Anterior • Posterior

25. Function • Controlled mostly by the brain. • Releasing hormones – hormones the brain (hypothalamus) secretes to signal the pituitary to release its hormones. • Each releasing hormone acts on a specific part of the pituitary.

26. Hormones - Anterior • Human Growth Hormone (HGH) • Stimulates cells to increase in size and divide more frequently. • HGH is released when there are low protein or sugar levels in the blood. • Disorders:

27. Hormones - Anterior • Prolactin (PRL) • Pro- = with, for • -lactin = milk • Stimulates milk production in females. • PRL is found in males. • Excess PRL in males decreases the amount of male sex hormones.

28. Hormones - Anterior • Thyroid-Stimulating Hormone (TSH) • Controls the secretion of hormones by the thyroid. • Adrenocorticotropic Hormone (ACTH) • Controls the secretion of hormones by the adrenal gland.

29. Hormones - Anterior • Follicle-Stimulating Hormone (FSH) • Stimulates the gonads. • Gonads – reproductive organs • Testes in males • Ovaries in females • Remember what follicles are?

30. Hormones - Posterior • Antidiuretic Hormone (ADH) • Decreases urine formation. • Does this by lowering the amount of water secreted by the kidneys. • Stimulated by fluid levels in the body.

31. Hormones - Posterior • Oxytocin (OT) • Stimulates uterine contractions during childbirth. • Contracts smooth muscles in the uterus. • Stimulated by stretching of uterine and vaginal tissues.

32. Section 11.6 Thyroid Gland

33. Structure • Consists of two lobes connected by the isthmus. • Just below the larynx and in front of the trachea.

34. Thyroid Hormones • Thyroxine (T4) • Regulates the metabolism of sugars, lipids, and proteins. • Determines how many calories you need to consume to live.

35. Thyroid Hormones • Triiodothyronine (T3) • Same function as Thyroxine, though this is 5 times more potent. • Both are stimulated by iodine levels in the body. • This iodine comes from food.

36. Thyroid Hormones • Calcitonin • Increases calcium and phosphate concentrations in the blood. • Does this by regulating osteoclast/osteoblast activity and the kidneys.

37. Thyroid Problems • Cretinism • Caused by not having enough thyroid activity (hypothyroidism). • Symptoms: • Stunted Growth • Abnormal Bones • Mental Retardation • Sluggishness

38. Thyroid Problems • Goiters • Too much thyroid activity (hyperthyroidism) leads to a swelling of the tissues behind it. • This causes a large bulge in the neck called a goiter.

39. Section 11.7 Parathyroid Glands

40. Structure • You have four. • They are very small. • Found on the posterior thyroid. • Covered in CT.

41. Parathyroid Hormone • Parathyroid Hormone (PTH) • Increases blood calcium levels and decreases blood phosphate levels. • Similar to calcitonin.

42. Section 11.8 Adrenal Glands

43. Structure • Located superior to the kidneys… sits on top of them like a cap. • Made up primarily of epithelial cells and blood vessels. • 2 parts: • Adrenal medulla – center • Adrenal cortex - outsides

44. Hormones – Adrenal Medulla • Epinephrine and Norepinephrine • Similar in structure and function. • Epinephrine is actually made from norepinephrine. • Several effects: • Increases heart rate. • Elevates blood pressure. • Increases blood sugar. • Addictive • ADRENALINE!!!

45. Disorders - Adrenaline • People who have too much adrenaline produced will suffer from high blood pressure, high blood sugar levels, increased heart rate, etc… hypertension.

46. Disorders - Adrenaline • Those who do not have enough adrenaline produced may be lackadaisacal and/or unexcitable – hypotension.

47. Hormones – Adrenal Cortex • Aldosterone • Helps regulate the concentration of minerals. (Na and K) • Does this by increasing water retention.

48. Hormones – Adrenal Cortex • Cortisol • Increases glucose levels in the blood. • Very similar to T3 and T4.

49. Hormones – Adrenal Cortex • The adrenal cortex also produces some sex hormones. • This is not the primary source of these hormones, however, so we will talk about them more once we get to the gonads next week.

50. Section 11.9 The Pancreas