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BIOLOGY: Homoeostasis

Control Systems:
­ Cells only work if the conditions are correct.
­ Automatic control systems keep the body conditions constant.
­ Keeping a constant environment is called homoeostasis.
­ Receptors are to detect stimuli.
­ Processing centres receive information and coordinate responses.
­ Effectors produce responses.
­ A…

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­ Temperature receptors in the brain detect the bloods temperature (in the hypothalamus)
­ A processing centre in the brain (in the hypothalamus) which receives information about from
receptors and triggers responses in effectors.
­ Effectors such as sweat glands and muscles.
­ High body temperatures: body makes sweat. Sweat…

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­ Send all the urea and some water and salt to the bladder. This is urine stored in the bladder then
later excreted.
­ They reabsorb molecules that the body needs, including all the glucose and some water and salt,
back into the blood.
­ Control water levels by making…

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Changing Momentum: When a resultant acts on the object, the momentum of the object changes in the
direction of the force. If the resultant force on an object is zero, its momentum does not change. If its
stationary, it stays still. If it is already moving, it continues at a…

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Sodium melts and whizzes round on surface of water. Sometimes, hydrogen catches fire
Potassium melts and may jump from surface of water. Hydrogen immediately catches fire
­ Alkali metals also react vigorously with chlorine gas to make chlorides.
­ The chlorides are colourless crystalline solids
e.g. lithium + chlorine lithium…

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Balancing Equations:
­ Make the number of atoms on each side of the arrow the same.
­ Balancing an equation means making both side of the equation the same.


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