Biology 12, homeostasis in action

How is your body temperature controlled?
-By the thermoregulatory centre found in the brain -It contains receptor cells that detect changes to blood temperature as small as 0.5*C -Sensors in the skin also feedback information of skin tmperature
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How does vasodilation help maintain a normal body temperature?
-The body temperature is too high -The blood vessels supplying capillaries close to the surface dilate -Heat is loss by radiation -Temperature returns to normal
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How does sweating help maintain a normal body temperature?
-Body temperature is too high -Glands near skin surface produce sweat -Heat transfers from blood to sweat where it evaporates -Temperature returns to normal
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How does vasoconstriction help maintain a normal body temperature?
-Body temperature is too low -Blood vessels supplying capillaries close to the surface constrict -Blood flow near the skin surface is reduced -Heat loss by radiation is reduced -Body temperature returns to normal
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How do hairs help maintain a normal body temperature?
-Body temperature is too low -Muscles near surface of skin contract (hair erector muscles) -Hairs on skin surface stand up -A layer of air is trapped -Heat transfer to surroundings is reduced as air, a gas, is a poor conductor
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How does shivering help maintain a normal body temperature?
-Body temperature is too low -Muscles contract involuntarily -Increased rate of cellular respiration to supply cells with sufficient energy -More thermal energy is transferred -Body temperature returns to normal
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How does water leave the body?
-You have no control over it -It leaves the lungs, along with carbon dioxide, when you exhale -Also leaves along with mineral ions through sweat
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How is urea excreted from the body?
-The liver removes the amino group from the protein(deamination), forming ammonia -Ammonia is immediately converted to urea which is still toxic but the body can remove it by the kidneys filtering it out from the blood and into urine
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What is stage one of the kidneys filtering the blood?
-Ultrafiltration -Glucose, mineral ions, urea and water all move from the blood to the kidney tubules -Blood cells and proteins are too big so remain in the blood stream
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What is stage two of the kidneys filtering the blood?
-Selective reabsorption -All the blood glucose is reabsorbed into the blood by active transport -The amount of mineral ions and water reabsorbed varies, it depends on what your body needs
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How does the hormone ADH affect selective reabsorption?
-Receptor cells in the brain detect the water concentration in the blood -If it is too low the pituitary gland released more ADH -This means the kidney tubules reabsorb more water & you will produce a small amount of concentrated urine and vice-versa
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What is the composition of the dialysis fluid when it enters the dialysis machine?
-When it enters there will be no urea to provide a steep concentration gradient so it will exit the blood -There will be a normal level of glucose and minerals so there is no net movement of glucose and any excess minerals can be removed
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What is the composition of the dialysis fluid when it exits the dialysis machine?
-When it exits there will be a high concentration of urea as the urea from the blood will have diffused -There will be the same amount of glucose (no net movement) -There may be a slight increase in mineral ions as any excess will have diffused
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What are the positives of a kidney transplant over dialysis?
-Patient can have a normal lifestyle -One procedure rather than regular dialysis sessions -Increased life expectancy -Cheaper for the NHS
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What are the negatives of a kidney transplant over dialysis?
-Shortage of kidneys -May be rejected, must take immunosuppressants for the rest of life -Invasive operation -May not be effective -Doesn't last forever, normally 12-15 years
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Other cards in this set

Card 2

Front

How does vasodilation help maintain a normal body temperature?

Back

-The body temperature is too high -The blood vessels supplying capillaries close to the surface dilate -Heat is loss by radiation -Temperature returns to normal

Card 3

Front

How does sweating help maintain a normal body temperature?

Back

Preview of the front of card 3

Card 4

Front

How does vasoconstriction help maintain a normal body temperature?

Back

Preview of the front of card 4

Card 5

Front

How do hairs help maintain a normal body temperature?

Back

Preview of the front of card 5
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