Understanding the Endocrine System: Hormones and Gland Functions

1. Unit 8: Endocrine System

2. Function • Coordinates and directs the activity of the body’s cells • This is the same function of the nervous system • However: • Nervous system: signals are specific and fast-acting • Endocrine system: signals are wide-spread and long-lasting

3. Physiology: How does it work? • Hormones: chemical messengers that are released into the bloodstream and transported throughout the body • A given hormone only affects certain tissues or organs • Referred to as target cells or target organs

4. Lock and Key Model • Only certain hormones will affect certain organs because of the presence of the right receptor

5. Hormones • 2 classes: • Steroid hormones: comprised of fats • Nonsteroid hormones: comprised of proteins or amino acids

6. Steroid Hormones • Hormones can pass straight through the cell membrane • Often derived from cholesterol • Lipid soluble • Let’s draw our own picture!

7. Nonsteroid Hormones • Hormones interact with the cell’s plasma membrane and initiate a cascade of signals that will occur within the cells • This is known as a second messenger system • Hormone = first messenger • Cascade of messengers and signals within the cell = second messenger • Let’s draw our own picture!

8. What do hormones control? • Reproduction • Growth and development • Mobilizing body’s defenses • Maintaining chemical homeostasis • Cellular metabolism and energy balance

9. How do hormones provide control? • Negative feedback • Hormones secretion inhibits further hormone release • Example: Ovaries release a hormone called estrogen. • When the ovaries release enough hormone to cause a slight increase in concentration in the blood, the ovaries stop secreting hormone • Let’s draw a picture of this!

10. Glands • There are many major endocrine glands in the body • Examples: • Hypothalamus • Pituitary • Thyroid • Parathyroid • Thymus • Adrenal gland • Pancreas • Ovary • Testis • Pineal Gland

11. WS #1 Endocrine Glands of the Body

12. Glands • The hypothalamus and pituitary glands are the head honchos of the endocrine system • In charge of controlling the release of all other hormones

13. Pituitary Gland • Controlled by the hypothalamus • Size of a grape • Sits on a bone called the sellaturcica (Turkish saddle) • 2 functional lobes • Anterior pituitary • Glandular tissue • Posterior pituitary • Nervous tissue

14. Pituitary Gland: Anterior Lobe • The anterior portion secretes hormones called tropic hormones • Stimulate target organs • Some are endocrine and some nonendocrine • All tropic hormones are • Nonsteroid hormones • Question: Where is the receptor located on the target cell? • On the plasma membrane!

15. Tropic Hormones

16. Let’s Make a Table!

17. Whiteboard practice!

18. Pituitary and Hypothalamus relationship • Anterior pituitary is controlled by the hypothalamus • The hypothalamus produces releasing and inhibiting hormones that control the release of the tropic hormones into the bloodstream

19. Hypothalamus Hormones • The releasing hormones are really easy to remember! • If the anterior pituitary is secreting growth hormone (GH), it was stimulated by growth hormone releasing hormone (GHRH) from the hypothalamus

20. Releasing Hormones • Predict: What tropic hormones will be secreted when the pituitary is stimulated with the following hormones? • Thyroid releasing hormone? (TRH) • TSH • Corticotropin-releasing hormone? (CRH) • ACTH • Gonadotropin-releasing hormone? (GnRH) • FSH/LH

21. Putting it all together with negative feedback • All of the hormones we have talked about exhibit negative feedback • Releasing hormone  tropic hormone  hormone • That is, the release of the target organ’s hormone will REPRESS the release of the hypothalamus and pituitary hormones

22. Let’s Draw a Picture!

23. Whiteboard practice!

24. Focus: Thyroid • 1) hypothalamus secretes TRH • 2) TRH stimulates the anterior pituitary to release TSH • 3) TSH travels to target organ (thyroid) • 4) Thyroid produces thyroid hormone

25. Thyroid Hormone • Function: Increase a person’s basal metabolic rate (BMR) (speed up their metabolism) and increase heat production • Question: If thyroid hormone exhibits negative feedback of further thyroid hormone production, excess thyroid hormone would cause ____________ and ___________ to stop being released. • TSH and TRH • This is negative feedback at work, folks!

26. Too Much? To Little? • Hyperthyroidism: excessive production of thyroid hormone • Causes Graves’ disease • Symptoms: constant feeling of warmth (as a result of increased BMR), weight loss, nervousness, and enlarged thyroid gland (goiter) • Hypothyroidism: decreased production of thyroid hormone • Symptoms: lower BMR (intolerance of cold), decreased appetite, weight gain

28. Focus: Adrenal Glands • 1) hypothalamus releases CRH • 2) CRH stimulates the anterior pituitary to release ACTH • 3) ACTH travels to target organ (adrenal glands) • 4) Adrenal glands produce cortisol

29. Question • If there is a high concentration of cortisol in the blood, the hypothalamus will release _______________ CRH. • A: more • B: less • CRH  ACTH  Cortisol

30. Cortisol • Function: promotes the breakdown of proteins and fats and helps the body adapt to stress • Provide the body with fuel to break down materials in the body • Can also act as an immunosuppressive and anti-inflammaory • Can shrink organs in the immune system • Ie thymus gland

31. Too Much? Too Little? • Hypercortisolism: excessive amount of cortisol • Causes Cushing’s syndrome • Symptoms: personality changes, hypertension (high blood pressure), osteoporosis, and weight loss • Hyposecretion: decreased secretion of cortisol • Symptoms: defective metabolism, mental confusion, decreased ability to adapt to stress

32. Focus: Gonads • 1) hypothalamus releases GnRH • 2) GnRH stimulates the anterior pituitary to release LH • 3) LH travels to the gonads (ovaries and testes) • 3) Gonads secrete sex hormones (estrogen and testosterone)

33. Testosterone • Function: Secondary sex characteristics of males • Increased body hair and deeper voice

34. Too Much? Too Little? • Too much testosterone? • Increased muscle mass • Male pattern baldness • Acne • Premature sexual development • Decreased amount of testosterone? • Abnormal sexual development • Low sperm count

35. Rule of Thumb • The more a gland is activated, the larger it gets • Known as hypertrophy (an increase in size) • Think about a person lifting weights—the more you use that muscle, the bigger your muscles get! • If a gland is continually inhibitied, it will shrink in size • Known as atrophy(shrinking in size)

36. Predict: • Let’s say your glands are 100% normal and they are working properly. • However, your target organs changed their “locks” AKA their receptors • Would they be responsive to hormones? • What would happen if a person with an XY chromosome was born with an insensitivity to testosterone?

37. Androgen Insensitivity Syndrome • The receptors on the target cells for testosterone (for example, the ones in the gonads) are unresponsive to testosterone • This would have occurred since birth—this is a congenital disease • The female set-up is default • Without testosterone, you would end up looking like a female on the outside • These individuals spend their whole lives thinking that (and looking like) they are female until puberty • They would grow the secondary sex characteristics (breasts), but menstruation would not occur • This is usually the time when they diagnose this disease • https://www.youtube.com/watch?v=JjI-RvkjujI