A2 Biology Unit 5 Flashcards - Homeostasis

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What is homeostasis?
Maintenance of a constant internal temperature
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Explain what happens when heat is lost and the body core temperature goes down (how is it detected)
The change in body temperature is detected by the hypothalamus which detects the decrease in blood temperature which then activates the heat gain centre via neurones
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What changes are brought about by the heat gain centre?
Vasocontriction, shivering, raising of hair, increased metabolic rates, decreased sweating
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What is vasoconstriction?
Where the arterioles constrict which reduces the amount of blood reaching the skin's surface so less heat is lost
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What changes are brought about by the heat loss centre?
Vasodilation, increased sweating, lowering of body hair, decreased metabolic rates
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What is vasodilation?
Diameter of arterioles near the surface of the skin dilate so blood flood the capillaries near the skin's surface
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Explain the second messenger model
The hormone = 1st messenger binds to specific receptors on cell surface membrane on target cells which forms hormone-receptor complex. This produces enzymes which produce a chemical (second messenger) causes chemical changes to produce response
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Which cells are larger and produce hormone glucagon?
Alpha cells
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What are Beta cells?
Smaller and produce the hormone insulin
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Name the 3 sources of Glucose
From the diet, from the breakdown of glycogen (glycogenolysis) and gluconeogenesis (production of new glucose)
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Explain what happens when the blood glucose level of the body increases
The beta cells of the islet of langerhans in the pancreas detect a rise in the blood glucose and secret insulin
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What changes does Insulin bring about?
Activates the enzymes that converts glucose to glycogen and fat, increases storage of glucose
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What happens when the blood glucose level of the body decrease
The alpha cells of the islet of Langerhans detect a fall in blood glucose and respond by secreting glucagon directly into the blood
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What changes does Glucagon bring about?
Activates an enzyme that converts glycogen to glucose, increasing the conversion of amino acids and glycerol into glucose
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What is type 1 diabetes?
Insulin dependent diabetes where this is due to the body is unable to produce insulin, called 'early onset' diabetes as it usually begins in childhood.
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What is type 2 diabetes?
Insulin independent diabetes where normally the glycoprotein receptors on the body lose their responsiveness to insulin. Usually develops due to people's lifestyle eg; bad diet
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How is type 1 diabetes controlled?
Injections of insulin, cannot be taken by mouth as it is a protein and would be digested
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How is type 2 diabetes controlled?
Controlled by regulating intake of carbohydrates in the diet and matching this to the amount of exercise taken
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Other cards in this set

Card 2

Front

Explain what happens when heat is lost and the body core temperature goes down (how is it detected)

Back

The change in body temperature is detected by the hypothalamus which detects the decrease in blood temperature which then activates the heat gain centre via neurones

Card 3

Front

What changes are brought about by the heat gain centre?

Back

Preview of the front of card 3

Card 4

Front

What is vasoconstriction?

Back

Preview of the front of card 4

Card 5

Front

What changes are brought about by the heat loss centre?

Back

Preview of the front of card 5
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