12.1 Principles of homeostasis
Learning objectives:
• define term homeostasis
• explain the importance of homeostasis
• relate the concept of negative feedback to
homeostatic mechanisms
A2 AQA 2011 ad
Control of internal environment
List the factors that can
change
Name the control organs
What is the internal environment? ………………………………..
Why does it need to be controlled?
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Homeostasis
The maintenance of a constant environment
Why? Explain the significance of a constant
Temperature and pH
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Water potential
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What is the advantage to the organism?
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The maintenance of a constant environment =
the ability to return to the set point so maintain organisms
in a balanced equilibrium
How? What is the control mechanism?
Receptor –
detects change
from set point
Homeostatic mechanism
(control unit)
Effectorreverses change
back to set point
OUTPUT =change
INPUT =change
Set point/normal
Feedback loop
Coordination of control mechanism
Many receptors and effectors
Input from many parts of body
e.g. running
- temp receptors in hypothalamus indicate blood
temp high
- sweating results in cooling of skin- temp receptors in skin indicate skin cool
Consequence…………………………………………
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