Chapter 9: Chemical Signals Maintain Homeostasis

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

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

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

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

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

The Location of Endocrine Glands Growth Hormone Insulin

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

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

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

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

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

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

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

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

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

The Pituitary Gland Figure 6. Page 376

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

Figure 6. Page 376 The Pituitary Gland

Table 1. page 377 Pituitary Hormones