Necessary Life Functions (functions that humans must perform to maintain life)
- Maintaining Boundaries
- Nutrients (food)
- Oxygen - Approximately 20% of the air we breathe is oxygen. It is made available to the blood and body cells by the cooperative efforts of the respiratory and cardiovascular systems.
- Water - Accounts for 60 to 80% of body weight.
- Appropriate temperature - Normal body temperature is 98.6 degrees. If the body temp drops below, metabolic reactions become slower and finally stop.If body temp is too high, chemical reactions proceed rapidly and proteins breakdown.
- Atmospheric pressure - It refers to the force exerted on the surface of the body by the weight of air. Breathing and the exchange of oxygen and carbon dioxide in the lungs depends on appropriate atmospheric pressure.
*** The mere presence of these survival factors is not sufficient to maintain life. There must be appropriate amounts.