Homeostasis

1. Homeostasis 7th Grade Science Mr. Bombick

2. Examples of Homeostasis in Action • Shivering on a cold day • Breathing heavily after running • Feeling light-headed or dizzy after standing up too fast Processes are needed to keep the body systems in balance and operating within normal limits.

3. Homeostasis-Simple Definition • The regulation of the internal body systems and processes to keep a constant stable condition.

4. Homeostasis-Temperature • Humans, other mammals, and birds are all capable of keeping a constant internal body temperature with changes in external environmental temperatures (they are homeothermic or “warm-blooded” • With cold temperatures, homeostatic mechanisms try to prevent heat loss from the body • With hot temperatures, homeostatic mechanisms try to increase heat loss from the body

5. Homeostasis-Temperature (cont.) • Some examples of physiological responses to cold temperatures include decreasing peripheral blood flow (keeps warm blood near vital organs), increased metabolism of fat stores (fat is used to generate internal heat), decreased heart rate (blood only needs to be circulated to vital organs), and increased shivering (generates internal heat) • Some examples of physiological responses to hot temperatures include increased peripheral blood flow (allows loss of heat at skin), production of sweat (for evaporative cooling), increased heart rate (insure good peripheral blood flow), and increased respiration (increased need for energy)

6. Homeostasis-Energy • Energy balance must be maintained by the body to ensure sufficient energy for the body to function but prevent the excessive storage of energy within the body • The general equation for energy balance is as follows: Energy intake = internal heat produced + external work + storage

7. Homeostasis-Iron Metabolism • Iron is a very important element for normal body functions • Iron is used for hemoglobin in the blood which results in the ability of red blood cells to transport oxygen and carbon dioxide throughout the circulatory system • Excessive iron can be toxic to body systems by participating in harmful oxidizing reactions that damage cells • An intricate iron homeostatic system is present that detects iron concentrations in the body and increases or decreases uptake of iron from the digestive system

8. Homeostasis-Blood Components • Sugar is regulated by the hormones insulin and glucagon both secreted by the pancreas—when blood sugar levels are high insulin is secreted to store sugar as starch and when blood sugar levels are low glucagon is secreted to use stored starch to release sugar into the blood stream • Calcium is regulated by the hormones PTH (parathyroid) and calcitonin (thyroid); low blood calcium results in PTH releasing calcium from bone and high blood calcium results in calcitonin storing calcium in bone

9. Homeostasis-Blood Components (cont.) • Acid-Base homeostasis is done by the kidneys to ensure the blood is at the proper range of pH (measure of acidity); kidneys will remove various components to keep the proper pH range; this is a very important homeostatic mechanism since many pathologies ultimately end up with problems with acid-base balance • Osmoregulation of the blood ensures the concentration of chemicals in the blood are not too concentrated nor too dilute; the kidneys are important for removing or retaining important chemicals to maintain the proper osmotic pressure within the liquid systems of the body

10. Homeostasis-Blood Components (cont.) • Volume or fluid balance is maintained by the hormones Anti-Diuretic Hormone (ADH or vasopressin) and Aldosterone; fluid deficiency results in secretion of ADH to increase fluid retention by the kidneys and lower urinary output; fluid excesses results in secretion of aldosterone to decrease fluid retention by the kidneys and increase urinary output

11. Homeostasis—Hemostasis • Hemostasis is the homeostatic mechanism which halts the bleeding process • A major part of hemostasis is the blood coagulation process • Platelets (one of the many types of cells in the blood) are critically involved in the coagulation process • Several critical biochemical pathways of the body are involved with blood clotting

12. The End