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Chapter 39

Chapter 39. Sections 1 & 2. The Endocrine System. Made of glands that release their products into the bloodstream. Products can deliver messages throughout the body. Hormones.

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Chapter 39

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  1. Chapter 39 Sections 1 & 2

  2. The Endocrine System • Made of glands that release their products into the bloodstream. • Products can deliver messages throughout the body.

  3. Hormones • Chemicals that are released in one part of the body that travel through the bloodstream and affect the activities of cells in other parts of the body. • Bind to specific sites on cells. If a cell doesn’t have the site, it doesn’t respond to the hormone. • Target Cells are the cells that have receptors to the hormone.

  4. How do hormones and nerves compare? • Hormones • Response slower (minutes to days) • Chemicals travel through bloodstream. • Nerve Impulses • Response fast (fraction of a second). • “Chain” reaction to elicit response.

  5. Glands – organs that produce and release substances (excretions) • Exocrine glands • Release secretions directly to organs that use them • Examples: sweat, tears, digestive juices • Endocrine glands • Release secretions (hormones) into bloodstream • Examples: thymus, adrenal glands, testis, ovaries, etc.

  6. Hormone Action – Read the section on how hormones work (p. 999) and fill in your lecture notes. • Steroid Hormones • Produced from cholesterol (a lipid) • Can cross cell membranes easily • Nonsteroid Hormones • Include proteins, small peptides and modified amino acids. • Generally cannot pass through the cell membrane of target cell.

  7. Prostaglandins • “Local Hormones” • Modified fatty acids that are produced by a wide range of cells (not just those in the endocrine system). • Generally affect only nearby cells and tissues (which is why they’re called “local hormones”) • Why is aspirin associated with prostoglandins?

  8. Feedback Mechanisms – Remember These? • Controlling Metabolism • Thyroxine is a hormone that controls the rate of metabolism in the body. • It’s produced by the thyroid. • When thyroxine levels are low, hypothalamus secretes TRH (thyrotropin-releasing hormone) • TRH causes pituitary to produce TSH (thyroid stimulating hormone) • TSH acts on the thyroid to get it to produce more thyroxine. hypothalamus pituitary thyroid TRH TSH Thyroxine

  9. High levels of thyroxine inhibit the secretion of TRH and TSH. • This stops the release of additional thyroxine. hypothalamus pituitary thyroid TRH TSH Thyroxine Feedback

  10. Maintaining Water BalanceMajor Points • Exercise/Sweat  Body Loses Water •  Concentration of solute in blood increases •  Hypothalmus responds • signal pituitary to release ADH (antidiuretic hormome) •  ADH goes to kidneys where water reabsorption is decreased. •  Drink water •  pituitary releases less ADH •  kidneys remove water rom blood and original concentration is restored.

  11. Complementary Hormone Action • Some hormone systems have “opposite effect” hormones – one may increase the concentration of the chemical, the other will decrease it.

  12. Calcium Ion Regulation • Calcitonin (from the thyroid) • Decreases calcium • Parathyroid hormone (PTH) from the parathyroid gland. • Increases calcium

  13. Calcium Levels Too High • Thyroid secretes calcitonin. • This signals the kidneys to reabsorb less calcium as they form urine. • Reduces amount of calcium absorbed in the intestines • Stimulates calcium deposition in the bones.

  14. Calcium Levels Too Low • PTH released by the parathyroids. • Stimulates the intestine to absorb more calcium from food (along with vitamin D). • Causes kidneys to retain more calcium. • Stimulates bone cells to release some of the calcium stored in bone tissue.

  15. §39-2 Human Endocrine Glands • They’re everywhere • Regulate a wide variety of activities

  16. Pituitary Gland • Bean-sized structure at the base of the skull. • Anterior (front) and posterior (back) • Secretes nine hormones that regulate many body functions. • Controls the functions of several other endocrine glands. • Too much = gigantism; too little = pituitary dwarfism

  17. Hypothalamus • Above and attached to the pituitary. • Controls the secretions of the pituitary. • Interactions between the nervous and endocrine systems take place here.

  18. Thyroid Gland • Located at the base of the neck. Wraps around the upper part of the trachea. • Plays a major role in regulating the body’s metabolism. • Produces thyroxine (remember what that does?). This requires iodine.

  19. Hyper vs Hypo thyroidism

  20. Parathyroid Glands (four of ‘em) • Found on the back surface of the thyroid. • Hormones from here act to maintain homeostasis of calcium levels in the blood. • PTH also affects other organ systems to help provide proper nerve and muscle function and bone structure.

  21. Adrenal Glands • Sit on top of the kidneys. • Release hormones that help the body deal with stress • Two parts: • Adrenal cortex (outside) • produces corticosteroids. • Adrenal medulla (inside) • produces epinephrine and norepinephrine • Responsible for the “fight or flight” response when an organism is stressed.

  22. Pancreas • Has both endocrine and exocrine functions. • Produces insulin and glucagon to keep blood sugar levels stable. • Insulin stimulates cells to remove glucose out of the bloodstream • Glucagon causes break down of glycogen and release of glucose into the bloodstream. • Insulin’s target cells are found in the liver, skeletal muscles and fat tissue.

  23. Reproductive Glands (Gonads) • Produce gametes and secrete sex hormones. • In Females: • Gonads = Ovaries • Produce eggs • Estrogen, progesterone • In Males: • Gonads = Testes • Produce sperm • Testosterone

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