GCSE AQA Biology 1 Homeostasis

GCSE AQA Biology 1 Homeostasis

1. Definition: The maintenance of a constant internal environment

2. These things must be controlled...

   • Ion content
   • Water content
   • Body temperature
   • Blood sugar level

3. Ion content

   • Ions taken into body in food & absorbed into blood
   • If food contains too much - excess ions need to be removed
   • Some ions lost in sweat
   • Kidneys remove excess from blood - got rid of in urine

4. Water content

   • Taken into the body as food & drink
   • Lost in these ways...
     • Through the skin as sweat
     • Via the lungs in breath
     • Via the kidneys in urine
   • Balance between sweat & urine can vary...
     • On cold day/when you're not been exercising, don't sweat much, produce more urine which will be pale (diluted)
     • On hot day/when you're exercising, sweat a lot, produce less urine which will be darker(more concentrated)
       • Will lose more water through breath

5. Body temperature

   • In human body enzymes work best at 37 degrees C
   • Part of the brain is sensitive to blood temp. in the brain & receives messages from skin about skin temp.

6. Blood sugar level

   • Eating food containing carbs put glucose into blood from gut
   • Normal metabolism of cells removes glucose from blood, if you do vigorous exercise more is removed
   • Hormone (insulin) helps maintain right level so cells get constant supply of energy