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and Energy

Module 1: Communication and Homeostasis


Stimulus and response
Enzymes in the body require certain specific conditions. These include:

A suitable temperature
A suitable pH
An aqueous environment that keeps the substrates and products
in solution
Freedom from toxins and excess inhibitors

External environment
All organisms live in…

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Maintaining the internal environment of the cell

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The composition of the tissue fluid is maintained by the

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blood. This is the transport medium for products to and from the cells. In order to prevent build-up of
toxic products they are taken away by the blood and preceded from excretion. It is very important
for the concentrations of all substances in the bodies to be monitored so to…

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Blood pressure

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Carbon dioxide concentration

Negative feedback
To maintain a constant internal environment the following processes will occur.

Any change in the internal environment must be detected.
The change must be signalled to other cells
Carbon dioxide concentration.

Stimulus receptor communication pathway (cell signalling) effector response

Positive feedback
When positive feedback occurs…

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Temperature regulation in Ectotherms

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Adaptation How it helps Example
Expose body to the Enables more heat to Snakes
sun be adsorbed
Orientate body to Exposes larger Locusts
sun surface are from
more heat absorption
Orientate body Exposes lower Locusts
away from the sun surface are so that
less heat is absorbed

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evaporation of
water from lungs
Hairs on skin Hairs lie flat Hair stands on end
providing little trapping air pockets
insulation in air as insulation
Arterioles leading Pre capillary Pre capillary
to skin capillaries sphincters of sphincters
arterioles leading vasoconstict
to skin capillary's
Liver cells Rate of metabolic Heightened…


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