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Chapter 39

Chapter 39. Human Endocrine System. Endocrine System. Consist of endocrine glands that secrete hormones which regulate a wide range of activities in humans Hormones - are secreted by glands and diffuse directly into the bloodstream.

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Chapter 39

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  1. Chapter 39 Human Endocrine System

  2. Endocrine System • Consist of endocrine glands that secrete hormones which regulate a wide range of activities in humans • Hormones- are secreted by glands and diffuse directly into the bloodstream

  3. Note: Not all of the glands listed in this diagram are endocrine glands.

  4. (1) Hypothalamus • Small region of the brain • It controls the release of hormones by the pituitary gland • Considered to be a major link between the nervous system and the endocrine system

  5. Location of the Hypothalamus and Pituitary

  6. (2) Pituitary Gland • Located at the base of the brain • Called the “master gland” because it controls the activities of other glands • Secretes these major hormones: FSH, LH, ACTH, TSH, Prolactin, Ignore, GH or FLAT PIG

  7. Growth Hormone (GH) • This hormone controls the growth of the body by stimulating the elongation of bones

  8. Affects of Growth Hormone What movie is the above picture from? The Princess Bride

  9. André the Giant (May 19, 1946 – January 27, 1993) was a professional wrestler and actor, born André René Roussimoff in Coulomiers, France. He was at least 208 cm (6 feet 10 in) tall and believed by many to have been over 213 cm (7 feet) at his tallest. His great size was a result of excessive growth hormone, a condition known as pituitary gigantism, and led to him being dubbed "The Eighth Wonder of the World[1][2]."

  10. Thyroid Stimulating Hormone (TSH) • Stimulates the thyroid gland to produce its hormone thyroxin

  11. When thyroxine (T4) levels are too low, the hypothalamus releases more TRH, that in turn stimulates the anterior to produce more TSH, causing the thyroid to produce more thyroxine. As the thyroxine levels increase, a signal is sent back to the hypothalamus, causing it to release less TRH. When a change occurs that causes the release of a chemical that reverses the direction of that change, this is known as negative feedback.

  12. Follicle Stimulating Hormone (FSH) • Stimulates the activities of the ovaries and testes

  13. Adrenocorticotropic Hormone (ACTH) • ACTH stimulates the cortex of the adrenal glands to secrete steroid hormones such as cortisol, a hormone involved in the production of glucose in the liver from amino acid and lipid sources.

  14. (3) Thyroid Gland • Located in the neck below the larynx and in front of the trachea • This gland secretes thyroxin which contains iodine

  15. Thyroxin • Regulates the rate of metabolism in the body and is essential for normal physical and mental development • Secretion of thyroxin is regulated by TSH, which is secreted by the pituitary gland • Lack of iodine in the diet will lead to lack of thyroxin secretion. This produces enlargement of the thyroid gland and is called Goiter • Goiter- is the result of iron deficiency in the diet

  16. Goiter (enlargement of the thyroid gland)

  17. Thyroid with Goiter (Cells are enlarged) Normal Thyroid

  18. An Individual with Goiter

  19. (4) Parathyroid Gland • Are tiny oval glands embedded in the walls of the thyroid gland • Secretes parathormone • Parathormone controls calcium metabolism • Calcium is necessary for proper growth of teeth and bones, blood clotting, and nerve function

  20. (5) Adrenal Gland • Located on the top of each kidney • Each gland consists of two layers: Adrenal cortex Adrenal medulla

  21. Adrenal Cortex • Secrete steroid hormones that: a) regulate water balance and blood pressure by controlling the reabsorption of sodium salt into the blood from the kidneys b) stimulate the conversion of fat and protein into glucose (gluconeogenesis)

  22. Adrenal Medulla • Secretes adrenalin (epinephrine) • Adrenalin increases the blood sugar level and accelerates the heart and breathing rate • Known as the “fight or flight” hormone

  23. (6) Pancreas • Both an exocrine gland and an endocrine gland • The exocrine portion secretes digestive juices into the small intestine • The endocrine portion consists of small clusters or “islands” of hormone-secreting cells called the Islets of Langerhans • The Islet of Langerhans secrete insulin and glucagon

  24. The Islets of Langerhans secrete insulin and glucagon

  25. Location of Pancreas in Body Stomach Pancreas

  26. Insulin • Facilitates the entrance of glucose into the cells • Insulin lowers blood sugar levels by promoting the movement of sugar out of the blood and into the liver where it is stored as glycogen

  27. Glucagon • Stimulates the release of sugar from the liver and into the blood • Therefore: insulin  lowers sugar level in blood glucagon  raises sugar level in blood

  28. Diabetes • When the Islets of Langerhans fail to produce enough insulin • As a result, glucose that enters the cell decreases, and glucose levels in the blood increases

  29. (7) Gonads • Sex organs • Males- testes that secrete testosterone which influences the development of the male secondary sex characteristics • Females- ovaries that secrete estrogen which influences the development of secondary sex characteristics

  30. Negative Feedback • Is a type of self-regulation associated with endocrine regulation Functions like a thermostat. Only activated when there is a need. Shuts off once that need has been met.

  31. Negative Feedback • It operates on the principle that the level of one hormone in the blood stimulates or inhibits the production of another hormone Ex: TSH regulates the secretion of thyroxin by the thyroid gland

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