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biology 0610printed 162 · PDF 162
328 pagesrevision 46933
printed 162 · PDF 162
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Negative feedback is a mechanism which detects a move away from the set point
and brings about an action that takes the value back to the set point, which illustrates
the mechanism adopted by the liver in response to insulin or glucagon.
Controlling Body temperature
Hypothalamus is the part of brain which is involved in controlling the body
temperature
When the temperature around us decreases certain changes happen:
Muscles contract and relax quickly. They get the energy from respiration and due to
respiration some of the energy is lost as heat energy which is used to warm the body.
Metabolism may increase
The arterioles supplying blood contract. This is known as vasoconstriction.
Sweat glands reduce secretion. As sweat cools the body so its production is
minimised.
Hair erector muscle contracts pulling the hair up and making them stand and trapping
warmth around the body
When the temperature around increases, following changes occur:
Hair erector muscle relax causing the hair to lie flat so heat leaves the skin easily
The arterioles become dilated. This is known as vasodilation. As more blood flows in
arterioles near the surface more heat is loss
Sweat production increases and more is released. This has a cooling effect on the
body.
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