1. Human Endocrine System Aim: How does the endocrine system respond to a stimulus?

2. Endocrine System A.Contains glands that release chemicals or hormones into the bloodstream to regulate overall metabolism, homeostasis, growth & reproduction. B. Is slower than the nervous system because it takes time for chemical to reach its target.

3. The Endocrine System

4. Glands A.Organs located throughout the body that release hormones. B.Exocrine - discharge secretions through a duct to a targeted tissue. Example: digestive glands C.Endocrine - release secretions directly into the bloodstream (ductless).

5. Hormones A.Chemical messengers secreted by endocrine glands. B.Each hormone has a specific “target tissue” which may increase or decrease its activity (regulates). Example: Insulin

6. Hormone Secretions A.Not secreted at a constant rate. Rate will vary with the needs of the body. B.Positive Feedback 1. Reinforces the original change. 2. An increase in A will cause an increase in B. C.Negative Feedback 1. Response that opposes the original change. 2. An increase in A will cause an decrease in B. Example: Insulin/glucagon

7. Types of Hormones Methods of Secretions A.Steroid Hormones 1. “Lipid-like” able to pass through the cell membrane. 2. One messenger model - able to enter target cells & bind to receptors INSIDE the cell.

8. Types of Hormones Methods of Secretions B.Protein-type Hormone. 1. Cannot pass through the cell membrane. 2. Second messenger model - these hormones cannot enter cell, but bind to receptors on the cell membrane causing second messenger molecules to be produced.

9. Endocrine Glands A.Hypothalamus B.Pituitary C.Thyroid D.Parathyroid E.Thymus F.Adrenal G.Pancreas H.Gonads - Testes I.Gonads - Ovaries

10. Hypothalamus A.LOCATION: Within the brain connected to the pituitary gland. B.HORMONES: Regulatory factors. C.FUNCTION: Reads nervous system messages sent to brain. Responds by sending hormones that direct pituitary gland.

11. Pituitary (Master Gland) A.LOCATION: Brain B.HORMONES: 1. GH (growth Hormone) - controls growth (long bones). 2. TSH (Thyroid Stimulating Hormone) - stimulates secretion of thyroid hormone.

12. Pituitary (Master Gland) 3. FSH (Follicle Stimulating Hormone) - egg & sperm production. 4. LH (Leutinizing Hormone) - controls release of egg cells in ovaries; production of sex hormones in males & females. C. FUNCTION: Stimulates other endocrine glands. endocrine glands.

13. Thyroid A.LOCATION: Neck B.HORMONE/FUNCTION: 1. Thyroxine - regulates rate of metabolism in body cells. 2. Calcitonin - regulates blood calcium level by stimulating bone deposition if calcium is too high in blood.

14. Parathyroid A.LOCATION: Embedded in back of thyroid. B.HORMONE/FUNCTION: 1. Parathyroid - stimulates bone to release calcium if too low in blood.

15. Thymus A.LOCATION: Upper chest near the heart. B.HORMONE/FUNCTION: 1. Thymosin - stimulates the development of T-cell lymphocytes in children.

16. Adrenal Gland A.LOCATION: On top of kidneys B.HORMONES/FUNCTION: 1. Adrenaline - produces an emergency “fight or flight” response. Example: increase in heartbeat & respiration.

17. Pancreas (Islets of Langerhans) A.LOCATION: Digestive Tract B.HORMONES/FUNCTION: 1. Insulin - influences absorption of glucose form the blood into body cells (lowers blood glucose levels). 2. Glucagon - increases blood sugar level by signaling liver to convert glycogen to glucose.

18. Gonads -Testes A.LOCATION: Reproductive system B.HORMONES/FUNCTION: 1. Testosterone - stimulates development of male reproductive system. a. Promotes development of secondary sex characteristics.

19. Gonads - Ovaries A.LOCATION: Reproductive system B.HORMONES/FUNCTION: 1. Estrogen - stimulates development of female reproductive system. a. Promotes development of secondary sex characteristics. 2. Progesterone - helps regulate menstrual cycle & maintains uterus during pregnancy.

20. Endocrine System Disorders A.Diabetes: Under - secretion of insulin 1. High blood sugar level. B.Growth Hormone: 1. Over-secretion - giantism. 2. Under-secretion - dwarfism. C.Goiter: Enlargement of thyroid gland.