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Exam questions · Biology · The Kidneys

ADH and Water Balance (Higher tier)

  • 6 exam questions
  • 18 marks
  • 9 quick checks
  1. 1 State [1 mark]

    State the name of the gland that releases ADH.

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    Model answer

    The pituitary gland.

    Mark scheme

    • Pituitary gland — 1 mark
  2. 2 Describe [2 marks]

    Describe the effect of ADH on the collecting duct.

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    Model answer

    ADH makes the walls of the collecting duct more permeable to water, so more water is reabsorbed into the blood.

    Mark scheme

    • More permeable to water — 1 mark
    • More water reabsorbed — 1 mark
  3. 3 Explain [3 marks]

    Explain why a person who has not had a drink for a long time produces a small volume of dark urine.

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    Model answer

    The water content of the blood falls, so more ADH is released by the pituitary gland. ADH makes the collecting ducts more permeable, so more water is reabsorbed into the blood. So the urine has a small volume, and it is concentrated and dark.

    Mark scheme

    • More ADH released — 1 mark
    • Collecting duct more permeable, more water reabsorbed — 1 mark
    • Small volume of concentrated urine — 1 mark
  4. 4 Explain [3 marks]

    Explain what happens to the release of ADH after a person drinks a large amount of water.

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    Model answer

    The water content of the blood rises, and the hypothalamus detects it. The pituitary gland releases less ADH, so the collecting duct is less permeable, less water is reabsorbed, and a large volume of dilute urine is produced.

    Mark scheme

    • Water content rises, detected — 1 mark
    • Less ADH released — 1 mark
    • Less water reabsorbed, dilute urine — 1 mark
  5. 5 Explain [3 marks]

    Explain why the control of the water content of the blood is an example of negative feedback.

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    Model answer

    A fall in the water content causes the release of ADH, which causes more water to be reabsorbed, so the water content rises back to normal. When it is normal, less ADH is released. The response reverses the change.

    Mark scheme

    • Change causes ADH release — 1 mark
    • Response reverses the change — 1 mark
    • Less ADH when normal — 1 mark
  6. 6 Evaluate [6 marks]

    A person has a condition in which the pituitary gland does not release ADH. Predict the effects on the person's urine and explain them, and suggest how the person could be treated.

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    Model answer

    Without ADH, the walls of the collecting duct stay impermeable to water, so very little water is reabsorbed by osmosis. The person produces a very large volume of dilute urine, and loses a lot of water from the body. The blood becomes more concentrated, so the person is very thirsty, and could become dehydrated. The person could be treated by taking a drug that acts like ADH, for example as a nasal spray, so that the collecting duct is more permeable, and more water is reabsorbed. The person also needs to drink enough water.

    Mark scheme

    • Collecting duct impermeable without ADH — 1 mark
    • Little water reabsorbed by osmosis — 1 mark
    • Large volume of dilute urine — 1 mark
    • Dehydration or thirst — 1 mark
    • Treat with ADH or a similar drug — 1 mark
    • Drink enough water — 1 mark

Quick check

  1. 1

    Which gland releases ADH?

    1. AThe pancreas
    2. BThe thyroid
    3. CThe pituitary
    4. DThe adrenal gland
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    C: The pituitary

    The pituitary gland.

  2. 2

    What does ADH do?

    1. AMakes the collecting duct more permeable to water
    2. BMakes the glomerulus filter faster
    3. CMakes the bladder store urine
    4. DMakes the liver produce urea
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    A: Makes the collecting duct more permeable to water

    It makes the collecting duct more permeable to water.

  3. 3

    What happens to the urine when there is a lot of ADH?

    1. AA large volume of dilute urine
    2. BA large volume of concentrated urine
    3. CNo urine at all
    4. DA small volume of concentrated urine
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    D: A small volume of concentrated urine

    It is a small volume of concentrated urine.

  4. 4

    When is a lot of ADH released?

    1. AWhen the water content of the blood is too high
    2. BWhen the water content of the blood is too low
    3. CWhen the body is too cold
    4. DWhen blood glucose is high
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    B: When the water content of the blood is too low

    When the water content of the blood is too low.

  5. 5

    How does water move out of the collecting duct?

    1. ABy osmosis
    2. BBy active transport
    3. CBy photosynthesis
    4. DBy filtration
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    A: By osmosis

    By osmosis.

  6. 6

    After a large drink, what happens to ADH release?

    1. AMore is released
    2. BIt does not change
    3. CLess is released
    4. DIt stops for ever
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    C: Less is released

    Less ADH is released.

  7. 7

    What part of the brain detects the water content of the blood?

    1. AThe cerebellum
    2. BThe cortex
    3. CThe medulla
    4. DThe hypothalamus
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    D: The hypothalamus

    The hypothalamus.

  8. 8

    Why is urine dark on a hot day?

    1. AMore urea is made
    2. BIt is concentrated, because more water is reabsorbed
    3. CGlucose is added
    4. DIt is diluted
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    B: It is concentrated, because more water is reabsorbed

    It is concentrated, because more water is reabsorbed.

  9. 9

    What type of control is the control of water content?

    1. ANegative feedback
    2. BPositive feedback
    3. CNo feedback
    4. DRandom
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    A: Negative feedback

    Negative feedback.