Endocrine System

1. Endocrine System • Chemical Control

2. What are endocrine hormones? • Chemical signals from one cell to remote target cells. • Chemicals for direct cell-to-cell communication. • Chemicals that cross a gap between to adjacent cells.

3. Messenger Molecules • Cells must communicate with one another to coordinate cell processes within tissues and to maintain homeostasis. • Cell-to-cell communication is carried out via messenger molecules.

4. Three types of chemical signals are used for cell-to-cell communication.

5. Four methods of cell-to-cell communication are found in the human body, ranging from direct to remote communication.

6. A muscle cell needs to tell a neighboring muscle cell to contract. This will be accomplished by ___ communication: • Direct. • Synaptic. • Paracrine. • Endocrine.

7. When blood sugar is high, body cells must be stimulated to take up sugar. This is accomplished by ___ communication. • Direct. • Synaptic. • Paracrine. • Endocrine.

8. Aspirin helps relieve headaches because it: • Inhibits prostaglandin synthesis. • Stimulates prostaglandin synthesis.

9. Endocrine hormones • Produced by endocrine (“ductless”) glands and secreted into the bloodstream. • Endocrine hormones may affect a wide array of target cells to produce multiple effects. • Two types: peptides (small proteins) and steroids (lipids).

10. Hormones and Receptors

11. Peptide Hormones • Peptide hormones do not enter the cell directly. These hormones bind to receptor proteins in the cell membrane. • When the hormone binds with the receptor protein, a secondary messenger molecule initiates the cell response. • Because peptide hormones are water soluble, they often produce fast responses.

12. peptide or amino acid-derived hormone (first messenger) 2 Hormone–receptor binding activates an enzyme that catalyzes the synthesis of a second messenger, such as cyclic AMP 1 The hormone binds to a receptor on the plasma membrane of a target cell cyclic AMP- synthesizing enzyme (cytoplasm) (extracellular fluid) ATP active enzyme receptor product cyclic AMP (second messenger) 4 The activated enzymes catalyze specific reactions plasma membrane inactive enzyme reactant 3 The second messenger activates other enzymes nuclear envelope (nucleus)

13. Steroid Hormones • Steroid hormones enter through the cell membrane and bind to receptors inside of the target cell. • These hormones may directly stimulate transcription of genes to make certain proteins. • Because steroids work by triggering gene activity, the response is slower than peptide hormones.

14. steroid hormone (extracellular fluid) The hormone binds to a receptor in the nucleus or to a receptor in the cytoplasm that carries it into the nucleus 2 The hormone–receptor complex binds to DNA and causes RNA polymerase to bind to a nearby promoter site for a specific gene 3 1 A steroid hormone diffuses through the plasma membrane DNA plasma membrane hormone receptor ribosome RNA polymerase 5 The mRNA leaves the nucleus, then attaches to a ribosome and directs the synthesis of a specific protein product 4 RNA polymerase catalyzes the transcription of DNA into messenger RNA (mRNA) mRNA gene new protein nuclear envelope (cytoplasm) (nucleus)

15. If receptors for a hormone were blocked, the effect would be the same as if: • More hormone was added. • No hormone had been released. • More receptors had been added. • The receptors had not been blocked.

16. Your doctor injects a hormone as a treatment for a condition, and says it won’t take effect for at least 24 hours. What kind of hormone was used? • Peptide • Steroid • Amino acid derived

17. W O R K T O G E T H E R • How do endocrine hormones “know” which cells are their target cells?

18. Role of the Hypothalamus • The thalamus receives sensory information, relays some to the hypothalamus. • Hypothalamus monitors the body for temperature, pH, other conditions. • Hypothalamus signals pituitary gland if conditions need to be corrected.

19. Role of the Pituitary • The pituitary is the “master gland” that signals other glands to produce their hormones when needed. • The anterior lobe of the pituitary receives signals from the hypothalamus, and responds by sending out the appropriate hormone to other endocrine glands. • The posterior pituitary receives oxytocin or antidiuretic hormone (ADH) from the hypothalamus, relays them to the body as necessary.

20. hypothalamus Neurosecretory cells of the hypothalamus produce oxytocin and ADH 1 Neurosecretory cells of the hypothalamus produce releasing and inhibiting hormones 1 Releasing or inhibiting hormones (green circles) are secreted into capillaries feeding the anterior lobe of the pituitary 2 2 Oxytocin and ADH (blue triangles) are secreted into the blood via capillaries in the posterior pituitary blood flow pituitary (anterior lobe) endocrine cell pituitary (posterior lobe) capillary bed Endocrine cells of the anterior pituitary secrete hormones (red squares) in response to releasing hormones; the pituitary hormones enter the bloodstream 3 capillary bed blood flow

21. Pituitary Hormones

22. Endocrine Hormones

23. W O R K T O G E T H E R • Use the table on the last slide to diagnose the following endocrine issues: • A patient who feels cold and listless all the time. • A patient who is constantly keyed up and nervous. • An elderly patient who is having chronic trouble falling asleep at night.

24. Homeostasis and Hormones • Examples: • Thyroid and temperature control • Thyroid, Parathyroid, and calcium • Pancreas and glucose control

25. W O R K T O G E T H E R • Knowing the following: • The thyroid produces thyroxine, which increases metabolism. • Thyroid-stimulating hormone is released by the pituitary. • Sketch a negative feedback loop that controls body temperature regulation.

26. Temperature Control

27. W O R K T O G E T H E R • Knowing the following: • Calcitonin from the thyroid inhibits calcium release from the bones. • Parathyroid hormone stimulates release of calcium from the bones. • Sketch a negative feedback loop that controls blood calcium level.

28. Blood Calcium

29. W O R K T O G E T H E R • Knowing that: • Insulin from the pancreas lowers blood glucose by stimulating body cells to take up glucose. • Glucagon from the pancreas increases blood sugar by stimulating the liver to break down glycogen into glucose. • Sketch a negative feedback loop that controls blood sugar.

30. Blood Sugar Control

31. W O R K T O G E T H E R • Given this patient profile, can you make a diagnosis? • Age – 14 • Gender – Male • Exam: Normal weight, low blood pressure • Lab tests: High blood glucose, low levels of insulin.

32. W O R K T O G E T H E R • Now how about this patient? • Age – 40 • Gender – Male • Exam: Obese, high blood pressure • Lab tests: High blood glucose, normal levels of insulin.

33. Other hormone roles • Controlling sleep cycles (melatonin) • Controlling reproductive cycles (melatonin, sex hormones) • Growth (growth hormone) • Responding to stress or emergencies (epinephrine and other hormones)

34. Hormones Everywhere! • Many other organs besides the endocrine glands produce hormones. • Kidneys produce several hormones that regulate blood pressure, which is essential for kidney function. • The digestive system produces several hormones that regulate appetite.

35. The obese mouse on the left does not produce enough leptin, a hormone produced by fat cells. Low body fat stimulates leptin production, which stimulates appetite. The mouse is obese because its low leptin levels give it an enormous appetite. Leptin injections return the mouse’s weight to normal. Humans sometimes have a leptin issue, too, but the problem is a bad leptin receptor on body cells. Alas, leptin injections won’t cure that.

36. Finally… • Summarize the roles of the pituitary and other endocrine glands in maintaining homeostasis in the human body.