1. Chapter 9: Chemical Signals Maintain Homeostasis

2. Recap The last section (7.6) discussed the following: Water Balance
Change in osmolity  release of ADH
Change in solute concentration and body volume  release of Aldosterone
Both those systems are examples of negative feedbacks
pH is regulated by the carbonic acid/bicarbonate buffer

3. To clarify Angiotensinogen ---------------> Angiotensin
Renin (enzyme)

4. Hormones
Chemicals released by cells in one part of the body that affect another part
A small amount is required
They serve as regulators, slowing down or speeding up processes
Endocrine hormone:
Chemicals secreted by endocrine glands directly into blood
The circulatory system is involved

5. Endocrine Glands at Work
Endocrine hormones are chemicals involved with the regulation of growth, development and homeostasis

6. Hormones are classified based on their activation site
Non-target Hormones
Target Hormones
These hormones affect many cells throughout the body
Growth Hormone (GH) or Somatotropin (ST)
Regulates development of long bones
Insulin
Regulates blood sugar levels
Epinephrine
Also known as adrenaline
Produced in times of stress
These hormones affect specific cells or target tissues
Parathyroid Hormone
Regulates calcium levels in the body
Gastrin
Stimulates cells of the stomach to produce digestive enzymes

7. The Location of Endocrine Glands
Growth Hormone
Insulin

8. Chemical Messages and Organ Activity
Mering and Minkowski (1889)
Removed the pancreas from one group of dogs
Their observations?
Dogs became fatigued (symptoms resemble diabetes)
Ants were attracted to the dogs without pancreas
Why?
Urine contained glucose (sugar) that ants were attracted to
Pancreas produce insulin to monitor blood sugar

9. Chemical Signals How do hormones signal cells?
Hormones do not affect all cells
Cells may have receptors for one hormone but not another
The numbers of receptors found on cells can vary
Liver and muscle cells have many receptor sites for the hormone insulin

10. There are two types of hormones
These two hormones differ in chemical structure and action
Steroid Hormones
Protein Hormones

11. Steroid Hormones Are made from cholesterol, a lipid compound
Includes male and female sex hormones and cortisol
Composed of complex rings of carbon, hydrogen and oxygen
Not soluble in water, but are soluble in fat

12. Steroid Signaling Figure 4. page 374
Hormones diffuse from capillaries to interstitial fluid
Note the target cell attaches to the receptor in the cytoplasm
Attaches to chromatin that has complementary shape

13. Protein Hormones This includes insulin and growth hormone (GH)
Contain chains of amino acids in varying length
Differ from steroid hormones  protein hormones ARE soluble in water

14. Protein Signaling Figure 5. page 375
Combines with receptor on the cell membrane.
Hormone-receptor complex produces an enzyme called adenylyl cyclase
Cyclic AMP acts as a secondary messenger to activate enzymes

15. The Pituitary Gland: The Master Gland
Why is it called the master gland?
It exercises control over the other endocrine glands
Connected to the hypothalamus – the area associated with homeostasis
Produces and stores hormones
Nerves stimulate hypothalamus which causes the release of hormones by the pituitary gland

16. The Pituitary Gland: Posterior Lobe
The pituitary gland consists of two separate lobes: the posterior lobe and the anterior lobe
Posterior lobe stores and releases
ADH, oxytocin
Hormones travel on specialized nerve cells from the hypothalamus to be stored in the pituitary and are released into the blood when needed

17. The Pituitary Gland
Figure 6. Page 376

18. The Pituitary Gland: Anterior Lobe
The anterior lobe of the pituitary gland produces its own hormones.
The anterior lobe is connected to the hypothalamus by nerves
Hormones secreted by nerve ends of the cells of the hypothalamus
Hormones transported in the blood to the pituitary gland
This causes the release of pituitary hormones
Pituitary hormones are carried in blood to target tissues

19. Figure 6. Page 376
The Pituitary Gland

20. Table 1. page 377
Pituitary Hormones