Ch. 18 – The Endocrine System

1. Ch. 18 – The Endocrine System

2. What is the system? • Functions • Made up of glands that produce and secrete hormones (chemical messengers • Regulation of growth, metabolism, and sexual development • Responses to stress and injury • Internal balance of body systems (homeostasis)

3. Hormones • Are chemical messengers that act on target cells or organs • Endocrine – secretions within the body • Exocrine – secretions outside the body (sweat)

4. Hormone Action • Hormones can: • Attach to cells and cause change (water-soluble hormones) • Diffuse into cells and cause change (steroid and thyroid hormones)

5. Major Structures

6. Hormone Control • The pituitary is often called the “master gland” • It is controlled by the hypothalamus in the brain. • Negative Feedback System • When hormone levels rise, the organ that secretes the hormone is switched off.

7. Hormone Control

8. Anterior Pituitary Hormones • Prolactin (PRL) • Growth hormone (GH) • Adrenocorticotropin (ACH) • Thyroid-stimulating hormone (TSH) • Luteinizing hormone (LH) • Follicle-stimulating hormone (FSH)

9. PRL and GH • Prolactin • Stimulates milk production in a woman’s breasts after childbirth • Can affect sex hormone levels from the ovaries in women and the testes in men • Growth hormone • Stimulates growth in children • Important for maintaining healthy body composition • In adults, important for maintaining muscle mass and bone mass • Can affect fat distribution in the body • Problems with the pituitary gland can result in dwarfism

10. Problems with GH

11. Problems with GH

12. Problems with GH

13. ACH and TSH • Adrenocorticotropin • Stimulates production of cortisol by the adrenal glands • Cortisol – “stress hormone” is vital to survival • Helps maintain blood pressure and blood glucose levels • Thyroid-stimulating hormone • Stimulates the thyroid gland to make thyroid hormones • Regulate the body’s metabolism, energy, growth and development, and nervous system activity

14. FSH and LH • Follicle-stimulating hormone • Promotes sperm production in men • Stimulates the ovaries to release eggs (ovulate) in women • Luteinizing hormone • Regulates testosterone in men and estrogen in women • These are gonadotropins **FSH and LH work together to allow normal functioning of ovaries and testes

15. FSH and LH

16. Posterior Pituitary Hormones • Oxytocin • Causes milk letdown in nursing mothers • Causes contractions during childbirth • Antidiuretic hormone (ADH) • Also called vasopressin • Regulates water balance • If this hormone is not secreted properly, this can lead to problems with sodium (salt) and water balance • This could also cause the kidneys not to work well

17. ADH and Diuretics • Diuretics – chemicals that increase urine production • Many common foods and drinks contain diuretics (alcohol) • Midol relieves symptoms of bloating because it increases urination

18. Thyroid Gland • Thyroid hormones control your metabolism • Which is your body’s ability to break down food • Store it as energy • Ability to break down food into waste products with a release of energy in the process

19. Thyroid Hormones • Thyroxin (T4) and Tri-iodothyronine (T3) • Both regulate the rate at which cells release energy from carbohydrates • Calcitonin • Regulates the blood concentration of calcium BMR – basal metabolic rate http://www.bmi-calculator.net/bmr-calculator/

20. Thyroid Problems • Thyroid hormones are partly made of iodine • Iodine is essential for making thyroxin • If a person doesn’t eat enough iodine, they can’t make thyroid hormones • The size of the follicle grows, the gland grows – goiter • If salt wasn’t iodized, most people wouldn’t get enough iodine

21. Goiter

22. Thyroid Problems • Hypothyroidism • Thyroid produces less hormone than normal • Symptoms – sensitive to cold, fatigue, joint or muscle pain, weight gain • Hyperthyroidism • Thyroid produces more hormone than normal • Grave’s disease • Symptoms – bulging eyes, fatigue, weight loss, increased sweating, heat intolerance

23. Hypothyroidism

24. Parathyroid Gland • Located behind the thyroid • Four tiny glands that maintain calcium and phosphate levels • PTH – parathyroid hormone – takes calcium from the bones and makes it available in the blood

25. Adrenal Glands • Located above each kidney • Epinephrine and norepinephrine • Increase heart rate, breathing rate, elevated blood pressure (fight or flight response) • Aldosterone • Helps maintain blood pressure • Cortisol • Keeps blood glucose levels stable • Adrenal sex hormones • Androgens (males) and estrogens (females)

26. Pancreas • Large gland behind stomach • Glucagon • Stimulates liver to break down glycogen, increases blood sugar concentration • Insulin • Decreases blood sugar concentration, affects uptake of glucose by cells

27. Diabetes • Diabetes – insulin deficiency • Blood sugar increases – excess is excreted in urine • Type 1 – inherited, juvenile-onset • Caused by immune disorder that destroys pancreatic cells • Type 2 – adult, mature-onset • Often occurs in individuals who are overweight • Can be controlled with diet and exercise • Body makes insulin, but excess fat interferes with body's ability to use the insulin correctly

28. Hypoglycemia • Insulin • Lowers blood sugar levels • Hypoglycemia can result • Can be cured with sugar injection or eating sugary foods This is why diabetics often carry candy with them.

29. Steroids • Anabolic steroids • Artificial steroids that mimic the function of androgens (male sex hormone) • These contribute to male characteristics such as muscle mass • The most powerful is testosterone