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Biology exam practise > Module 6- Control of blood water potential > Flashcards

Module 6- Control of blood water potential Flashcards

1
Q

Outline ultrafiltration to form glomerular filtrate

A
  1. Ultrafiltration occurs between the glomerulus and bowmans capsule
  2. High hydrostatic pressure created by afferent capillary wider than efferent capillary
  3. Small molecules pushed into nephron- water, urea, aa, glucose, ions (glomerular filtrate)
  4. Endothelium pores–> basement membrane (filter)–> gaps between podocytes
  5. Large proteins and blood cells remain in blood
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2
Q

Outline selective reabsorption of glucose and water in proximal convoluted tubule

A
  • Selective reabsorption starts in the PCT
  • Good blood supply, microvilli, many mitchondria
  • Na+ enter with glucose/ aa via co transporter protein
  • Na+/K+ pump removes Na+ via active transport (requires ATP)
  • ALL glucose/ aa returned to blood via FD
  • Water potential lowers. Water moves into cell by osmosis
  • Some urea returns to blood via diffusion
  • 70% water, ions reabsorbed. 100% aa and glucose
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3
Q

Outline selective reabsorption of water in Loop of Henle by maintaining a gradient of sodium ions

A
  • Na+ actively transported out of the ascending limb [requires ATP].
  • Water potential of medulla lowered.
  • Ascending limb impermeable to water.
  • Water leaves descending limb via osmosis [from filtrate to medulla and then blood].
  • Hair- pin multiplier, counter current principle applies
  • Some Na+ diffuses into descending limb.
  • Longer the Loop of Henle – greater the conc gradient, more water+ ions reabsorbed
  • Apex of loop has the most concentrated filtrate
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4
Q

Outline osmoregulation in the Distal Convoluted Tubule and the collecting duct

A
  • Osmoreceptors in the hypothalamus detect water levels of blood.
  • Posterior pituitary gland releases ADH, if dehydrated
  • ADH binds to specific complementary receptors on target cells in Distal convoluted tubule and collecting duct.
  • Phosphorylase activated
  • Increased inclusion of water protein channels in membrane
  • Increase reabsorption of water via osmosis down a water potential gradient from filtrate to medulla to blood. Permeability of membrane to water is increased
  • Urine becomes more concentrated and lower in volume.
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5
Q

How does dialysis work?

A

Dialysis fluid concentration gradients are manipulated so that no glucose or amino acids are lost. All of urea is removed.

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6
Q

Give negatives of dialysis

A
  • Blood thinners required – can lead to blood clotting issues
  • Quality of life issues – time consuming.
  • Infection risk in hospital
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7
Q

Give negatives of kidney transplant

A
  • Difficulty to find donor match.
  • Immunosuppressant drugs required.
  • New transplant needed after 9 years.
  • Surgical risks.
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8
Q

2 marks

A high blood glucose concentration could cause glucose to be present in the urine of a diabetic person. Suggest how

A
  • large amount of glucose in filtrate
  • Cannot all be reabsorbed
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9
Q

3 marks

If the glomerular filtrate of a diabetic person contains a high concentration of glucose, he produces a larger volume of urine. Explain why.

A
  1. Glucose in filtrate lowers water potential
  2. Lower water potential gradient
  3. Less water reabsorbed via osmosis
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10
Q

3 marks

Explain how urea is concentrated in the filtrate

A

Reabsorption of water by osmosis
At the PCT / descending LoH
At the DCT / CD
Active transport of ions / glucose creates gradient (in context)

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11
Q

6 marks

Humans can produce urine which is more concentrated than their blood plasma.
Explain the role of the loop of Henle in the absorption of water from the filtrate.

A
  1. In the ascending limb sodium ions actively removed
  2. Ascending limb impermeable to water
  3. In descending limb sodium(ions) diffuse in
  4. Descending limb water moves out
  5. Low water potential
  6. The longer the loop, the lower the water potential in medulla
  7. Water leaves collecting duct
  8. By osmosis / down water potential gradient
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12
Q

4 marks

Explain the role of ADH in the production of concentrated urine.

A
  1. When water potential of the blood too low
  2. Detected by receptors in the hypothalamus
  3. Pituitary releases more ADH
  4. ADH increases the permeability/ opens channels for water in the DCT / collecting duct
  5. More water is reabsorbed into the blood
  6. By osmosis down the water potential gradient
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13
Q

2 marks

When a person’s dehydrated, the cell volume of an osmoreceptor falls. Explain why

A
  1. Water potential of blood will decrease
  2. Water moves from osmoreceptor into blood via osmosis
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14
Q

2 marks

The kangaroo rat is a small desert mammal. It takes in very little water in its food and it rarely
drinks. Its core body temperature is 38 °C.
The kangaroo rat takes in some water by feeding and drinking. Describe another method by
which the kangaroo rat could obtain water.

A

From aerobic respiration

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15
Q

4 marks

Some people who have diabetes do not secrete insulin. Explain how a lack of insulin
affects reabsorption of glucose in the kidneys of a person who does not secrete insulin.

A
  1. High concentration of glucose in blood
  2. High concentration in filtrate
  3. Reabsorbed by F.D
  4. Requires carrier proteins
  5. These are saturated
  6. Not all glucose is reabsorbed / some is lost in urine
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16
Q

Some desert mammals have long loops of Henle and secrete large amounts of antidiuretic
hormone (ADH). Explain how these two features are adaptations to living in desert
conditions

A

For general principle, applied to either example:
1. More water, from filtrate, is reabsorbed
2. Via osmosis
3. From collecting duct + distal convoluted tubule
4. Due to longer loop of Henle
For loop of Henle, maximum 2 marks:
5. Sodium ions absorbed from filtrate in ascending limb
6. Greater concentration gradient in medulla
For ADH, maximum 2 marks:
7. Acts on collecting duct + distal convoluted tubule
8. Causes increased inclusion of water channels (aquaporins) in membrane

17
Q

3 marks

Describe and explain how three features of the cells in the proximal convoluted tubule allow the rapid reabsorption of glucose into the blood.

A
  1. Microvilli provide a large surface area
  2. Many channel/carrier proteins for facilitated diffusion
  3. Many carrier proteins for active transport
  4. Many channel/carrier proteins for co-transport
  5. Many mitochondria produce ATP for active transport
  6. Many ribosomes to produce carrier/channel proteins
18
Q

3 marks

A decrease in blood pressure stimulates the release of ADH.
Give the location of the receptors that detect a decrease in blood pressure and explain how the release of ADH will affect blood pressure.

A
  1. Aorta + carotid
  2. Increased reabsorption of water
  3. Increases volume of blood and pressure increases
19
Q

5 marks

Some people who have diabetes do not secrete insulin. Explain how a lack of insulin affects reabsorption of glucose in the kidneys of a person who does not secrete insulin.

A
  1. High concentration of glucose in blood
  2. High concentration of glucose in the filtrate
  3. Reabsorbed by F.D.
  4. Requires carrier proteins
  5. Carrier proteins are saturated
  6. Not all glucose is absorbed and some is lost in urine
20
Q

In a mammal, urea is removed from the blood by the kidneys and concentrated in the filtrate.
Describe how urea is removed from the blood.

A

Hydrostatic pressure
Causes ultrafiltration at Bowman’s capsule
Through basement membrane
Enabled by small size urea molecule

21
Q

2 marks

Explain how the cells of the collecting duct are able to absorb water from the filtrate through the protein channels in their plasma membranes.

A
  • Lowers water potential
  • Water enters via osmosis
22
Q

2 marks

Furosemide inhibits the absorption of sodium and chloride ions from the filtrate produced in the nephrons.
Explain how furosemide causes an increase in the volume of urine produced

A

1.Water potential of filtrate/tubule decreased
2. Less water reabsorbed by osmosis from filtrate
3. Collecting duct is where osmosis occurs

23
Q

3 marks

Using your knowledge of the kidney, explain why glucose is found in the urine of a person with untreated diabetes.

A
  1. High concentration of glucose in blood/filtrate
  2. Not all the glucose is reabsorbed at the proximal convoluted tubule
  3. Carrier/co-transport proteins/ are saturated
24
Q

2 marks

Alcohol decreases the release of ADH into the blood.
Suggest two signs or symptoms which may result from a decrease in ADH.

A
  1. Dehydration/thirst
  2. Frequent urination/ Increase in volume of urine
    3.Less concentrated urine
25
Q

3 marks

Describe the effect of ADH on the collecting ducts in kidneys.

A
  1. Stimulates addition of channel proteins (aquaporins) into membrane
  2. Increases permeability to water/ More water reabsorbed;
  3. By osmosis
26
Q

2 marks

When a person is dehydrated, the cell volume of an osmoreceptor decreases. Explain why.

A
  1. Water potential of blood will fall
  2. Water moves from osmoreceptor into blood via osmosis

Biology exam practise (32 decks)

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