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Biology Revision
UNITS B4-B6…read more

Slide 2

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Homeostasis…read more

Slide 3

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Keeping conditions inside your body the same is called homeostasis.
It isn't easy as lots of things have to happen for the body to `stay the
same'. Such as:
Energy is transferred between the body and the environment
Carbon dioxide is a waste product of respiration. It is transported by
the bloodstream to the lungs, where it is breathed out.
Water from food and drinks passes through the gut wall and into the
Water and waste products, for example urea, are filtered out of the
blood and excreted in the urine.
Molecules from digested food pass through the gut wall into the
bloodstream. They are transported to the body cells to use for
growth and repair. Glucose is used in respiration.
Oxygen passes from the air in the lungs into the blood. It is taken in
the bloodstream to the body cells where it is needed for respiration.…read more

Slide 4

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How Does An Incubator Work
An incubator has a temperature sensor, a thermostat
with a switch, and a heater.
The temperature inside the incubator is detected by
the sensor. If the temperature falls, the thermostat
switches on the heater. When the temperature gets
back to 32C, the thermostat switches off the heater.
This is negative feedback.…read more

Slide 5

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Any change in the system results in an action that
reverses the change.
Thermostat Heater
system with (switched
Sensor a switch off)
Fall in
Rise in
Incubator temperature at 32C
Fall in Rise in
temp temp
Thermostat Heater
system with (switched
Sensor a switch on)…read more

Slide 6

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Control Systems With More Than One Effector
If two effectors have opposite effects, they are called
antagonistic effectors. You can use them to adjust the
system as soon as there is a change- either too fast or
too slow. This means the response is more sensitive.
Your body uses this system:
Processing Centre- Effector A- brings
Receptor- detects
receives and about change
increase processes info (decrease)
Increase from Fall back to
`normal' level `normal'
`Normal' or `ideal' level for system
Decrease from Increase back
`normal' level
to `normal'
Processing Centre- Effector B- brings
Temp Sensor receives and about change
processes info (increase)…read more

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