1. The Endocrine System Chapter 7

2. Learning Objectives Understand the general functions of the endocrine system. Be able to define the terms endocrine and hormone. Know the three basic chemical structures of hormones. Know the general mechanisms by which hormones alter cellular activity. Know the effects of exercise on hormone secretion.

3. Endocrine and Exocrine Glands Endocrine glands:  Secrete hormones into blood, which carries them to organs or systems where they have their effects. Exocrine glands:  Secrete their products through ducts to the exterior.  For example, sweat glands

4. Locations of Major Endocrine Glands Adapted from J.W. Hole, Jr. Human Anatomy and Physiology, 5th ed. (1990). Adapted with permission of The McGraw-Hill Companies.

5. Major Endocrine Glands

6. Major Endocrine Glands, continued

7. Hormones Biological chemicals secreted by an endocrine gland. Three categories: 1.Steroid hormones 2.Protein hormones 3.Phenolic amine hormones

8. The Three Basic Hormone Structures

9. Characteristics of Steroid and Protein Hormones Steroid hormones:  Are derived from cholesterol  Have a four-ring structure  Enter easily through the cell membrane Protein hormones:  Contain chains of amino acids  Are not lipid soluble  Cannot diffuse through the cell membrane

10. Action of a Steroid Hormone Adapted from J.W. Hole, Jr. Human Anatomy and Physiology, 5th ed. (1990). Adapted with permission of the McGraw-Hill Companies.

11. Action of a Protein Hormone Adapted from J.W. Hole, Jr. Human Anatomy and Physiology, 5th ed. (1990). Adapted with permission of the McGraw-Hill Companies.

12. Control of Hormone Secretion Three types of stimuli may initiate hormone secretion: 1.Neural 2.Hormonal 3.Concentration of a substance in the blood Secretion rates are usually maintained by a negative feedback mechanism.

13. Exercise and Endocrine Function Emerging evidence indicates: Effects of hormones on exercise performance are considerably important. Effects of exercise on endocrine function are also considerable.

14. The Pancreas Secretes glucagon and insulin, which play important roles in controlling the fuel supply to working tissues. Blood glucagon levels rise with strenuous exercise. Insulin levels decrease in direct proportion to increases in workload.

15. Clinical Application Diabetes Therapy Exercise is an effective therapy for Type II diabetes: Exercise and resistance training decrease insulin resistance and blood glucose levels. Changes are short lived (less than 72 hours). Moderate aerobic exercise needs to be done for at least 30 minutes every other day in order to maintain beneficial effects.

16. Your Perspective You’ve recommended to your diabetic client that he walk for two miles every other day after dinner. You find out that he’s exercising with heavy weights on alternate days. He says he’s never felt better. How do you counsel him?

17. The Adrenal Medulla Secretes epinephrine and norepinephrine (catecholamines), which increase the availability of fuel to active muscles Plays a role in exercise and training:  Increases in glycogenolysis, lipolysis, heart rate, and stroke volume  Redistribution of blood flow to working muscles and the skin  Improved mental performance

18. Thyroid and Parathyroid and Exercise Thyroid:  Important regulators of metabolism  Chronic exercisers and athletes have higher metabolic rates. Parathyroid:  Increases calcium levels in the blood  Relationship to exercise is unclear, but regular exercise plays an important role in producing/maintaining a healthy skeleton.

19. Gonads and Exercise Men:  Testosterone levels increase after high- intensity aerobic and anaerobic exercise and weight-lifting.  Acute submaximal and endurance training result in lower testosterone. Women:  Heavy exercise can result in delayed menarche, amenorrhea, and anovulation.  Luteinizing hormone (LH) drops after intense exercise, which may explain reproductive disturbances.

20. Your Perspective How would you counsel a male weightlifter with heightened testosterone levels or a female gymnast with delayed menarche? Does realizing that we don’t have complete knowledge about the hormonal response to exercise affect what you will say to these athletes?

21. Growth Hormone and Exercise Secreted by anterior pituitary Regulates growth and metabolism Responds to strenuous exercise by increasing hormone levels Effects of training on increase in growth hormone levels have not been established:  Differences in responses could be due to variables such as intensity, duration, and type of exercise; fitness level of subject, etc.

22. Where to Learn More Endocrine system:  www.emc.maricopa.edu/faculty/farabee/biobk/ www.emc.maricopa.edu/faculty/farabee/biobk/ BioBookENDOCR.html The Pituitary Foundation:  www.pituitary.org.uk/ www.pituitary.org.uk/ Growth hormone:  http://arbl.cvmbs.colostate.edu/hbooks/pathphys/end ocrine/hypopit/gh.html http://arbl.cvmbs.colostate.edu/hbooks/pathphys/end ocrine/hypopit/gh.html

23. NCSA CSCS Certification Standards— 1.F Understand human neuroendocrine physiology.  Describe training programs that you could develop for:  9–12 year-old girls  A teenaged boy who hasn’t yet had his growth spurt  College-aged men  Individuals with diabetes