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Changing to stay the same...

  • Keeping conditions inside your body the same is called Homeostasis.

Your body works hard too ;

Keep a constant body temprature .

Keep the correct levels of water and salt.

Control the amounts of nutrients, for example glucose.

Take in enough oxygen for respiration.

Get rid of toxic waste products, for example carbon dioxide and urea.

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Control Systems

Premature babies cannot control their temperature, so they are put in incubators. The incubator is an artificial control system.

The control systems keeping a steady state in your body work in a similar way to artificial control systems.

All control systems have:

  • A receptor, which detects the stimuli (the change)
  • A processing centre,which receives the information.
  • An effector,which produces an automatic response.


Homeostasis , Receptor , Processing centre and effector.

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Feedback in control systems

If the temperature in an incubator falls too low,the heater is switched on. The temperature goes up. When the temperature is high enough,the heater is switched off. This type of control is called negative feedback.

Antagonistic effectors are used in cars to keep it at a constant speed so it doesn't go to fast or two slow.


Negative feedback and antagonistic effectors.

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The chemical reaction that take place in cells rely on enzymes. Enzymes work best in certain conditions,for example at a certain temperature. This is important reason why you need a steady state inside your cells.

What are enzymes?

Enzymes are the catalysts that speeds up chemical reactions in living organisms. They are protiens - large molecules made up of long chains of amino acids.

In all cases, the molecules must fit exacly into a part of the enzyme called the active site. Its a bit like fitting  the right key in a lock.


Enzymes,Catalysts,Lock and Key Model and Active Site.

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not that good; very vague

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