12.1 Homeostasis

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  • Created by: Molly
  • Created on: 23-03-14 16:38
What is homeostasis?
The maintenance of a constant internal environment.
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List 3 reasons why homeostasis is important?
Enzymes - fluctuations in pH and temp affect enzyme activity. Water potential - could cause cells to expand/shrink. Organisms who are able to maintain a constant internal environment are less reliant on the external environment and are independant.
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List the sequence for a control mechanism.
Set point. Receptor. Controller. Effector. Feedback loop.
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What is positive feedback?
A process which results in a substance that departs from its normal level becoming further from its norm.
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What is positive feedback?
A series of changes that results in a substance being restored to its normal level.
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What is negative feedback?
a series of changes that result in a substance being restored to it's normal level.
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List 2 methods of heat gain?
Production of heat by metabolism of food. Gain of heat from environment, e.g. by conductor, convection, radiation.
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List 2 methods of heat loss?
Evaporation of water (sweating), loss of heat to environment via conduction, convection, radiation.
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Explain conduction.
Occurs in solids and is the transfer of energy through matter from particle to particle.
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Explain convection.
Occurs in gases/liquids. Heat causes fluid to expand and rise, carrying the heat it has absorbed.
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Explain radiation.
Energy is transferred by electromagnetic waves. When these waves hit an object they normally heat it up.
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What is an endotherm?
An organism that derives their heat from metabolic activities.
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What are ectotherms?
Organisms which obtain their heat from outside their body.
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How have mammals in cold climates evolved to keep warm?
Small surface area to volume ratio, makes it easier to maintain temperature as less heat is lost. Smaller extrematies e.g. ears, hair, to insulate the body.
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What happens in vasoconstriction?
Diamter of arterioles near skin restricts, reducing volume of blood reaching the surface of the skin via capillaries. Most of the blood therefore passes beneath the insulating layer of fat and so loses little heat to the environment.
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How does shivering cause you to warm up?
muscle contraction produces metabolic heat.
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How does raising of the hair warm you up?
Traps a layer of air which insulates the skin.
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What happens in vasodilation?
when the arterioles near the surface of the skin dilate allowing more blood to reach the surface of the skin and heat from this blood is radiated away from the body.
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How is a change in temperature detected?
Thermoreceptors in skin feel change in heat and send a message to the hypothalamus in the brain which cools the blood.
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Other cards in this set

Card 2

Front

List 3 reasons why homeostasis is important?

Back

Enzymes - fluctuations in pH and temp affect enzyme activity. Water potential - could cause cells to expand/shrink. Organisms who are able to maintain a constant internal environment are less reliant on the external environment and are independant.

Card 3

Front

List the sequence for a control mechanism.

Back

Preview of the front of card 3

Card 4

Front

What is positive feedback?

Back

Preview of the front of card 4

Card 5

Front

What is positive feedback?

Back

Preview of the front of card 5
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