GCSE AQA Biology 1 Homeostasis

Definition: The maintenance of a constant internal environment
These things must be controlled...
1. Ion content
2. Water content
3. Body temperature
4. Blood sugar level
Ion content
1. Ions taken into body in food & absorbed into blood
2. If food contains too much - excess ions need to be removed
3. Some ions lost in sweat
4. Kidneys remove excess from blood - got rid of in urine
Water content
1. Taken into the body as food & drink
2. Lost in these ways...
  1. Through the skin as sweat
  2. Via the lungs in breath
  3. Via the kidneys in urine
3. Balance between sweat & urine can vary...
  1. On cold day/when you're not been exercising, don't sweat much, produce more urine which will be pale (diluted)
  2. On hot day/when you're exercising, sweat a lot, produce less urine which will be darker(more concentrated)
    1. Will lose more water through breath
Body temperature
1. In human body enzymes work best at 37 degrees C
2. Part of the brain is sensitive to blood temp. in the brain & receives messages from skin about skin temp.
Blood sugar level
1. Eating food containing carbs put glucose into blood from gut
2. Normal metabolism of cells removes glucose from blood, if you do vigorous exercise more is removed
3. Hormone (insulin) helps maintain right level so cells get constant supply of energy

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