Homeostasis

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  • Created by: EmiLy1703
  • Created on: 10-12-17 15:31
What is homeostasis?
The maintenance of a stable internal environment
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What is negative feedback?
Keeps things around the normal level, e.g. body temperature is usually kept within 0.5 degrees above or below 37
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What is positive feedback?
One thing leads to another e.g. oxytocin in childbirth causes contractions
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Why is homeostasis necessary?
Keeping your internal environment stable is vital for cells to function normally and to stop them being damaged
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Why is it important to control blood pH?
If blood pH is too high or too low enzymes become denatured
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Why is it important to control blood glucose concentration?
If blood glucose is too high the water potential of blood is reduced to a point where water molecules difuse out of cells into the blood by osmosis, cause the cells to shrivel up and die. Too low, cells are unable to carry out normal activities
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Describe and explain what effect a very high body temperature has on metabolic reactions. (2 marks)
It makes metabolic reactions less efficient because the enzymes that control metabolic reactions may denature
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Describe the importance of multiple negative feedback mechanisms in homeostasis. (2 marks)
Multiple negative feedback mechanisms give more control over changes in the internal environment than just having one feedback mechanism. This is because you can actively increase or decrease a level so it returns to normal
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What do beta cells in the pancreas make?
Insulin
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What do alpha cells make?
Glucagon
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What are insulin and glucagon?
Hormones
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What is the role of insulin?
Lowers blood glucose concentration when it's too high
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What is the role of glucagon?
Raises blood glucose concentration when its too low
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How does insulin lower the blood glucose concentration?
Binds to specific receptors on liver and muscle cells, increase the permeability of membranes to glucose so they take up more glucose, activates enzymes that convert glucose into glycogen (glycognesis) which is stored in the cytoplasm.
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How does glucagon raise the blood glucose concentration?
Binds to specific receptors on membranes of liver cells, activates enzymes in liver cells that break down glycogen into glucose (glucogenolysis) and enzymes that are involved in the formation of glucose from glycerol and amino acids (gluconeogenesis)
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Other cards in this set

Card 2

Front

What is negative feedback?

Back

Keeps things around the normal level, e.g. body temperature is usually kept within 0.5 degrees above or below 37

Card 3

Front

What is positive feedback?

Back

Preview of the front of card 3

Card 4

Front

Why is homeostasis necessary?

Back

Preview of the front of card 4

Card 5

Front

Why is it important to control blood pH?

Back

Preview of the front of card 5
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