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HUBS192 2024 > Lecture 32 > Flashcards

Lecture 32 Flashcards

1
Q

What are the three places where water is reabsorbed in the nephron?

A

PCT, descending limb on nephron loop, collecting duct

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2
Q

How much water is reabsorbed in the PCT?

A

67%

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3
Q

How much water is reabsorbed in the descending limb of the nephron loop?

A

25%

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4
Q

How much water is reabsorbed in the collecting duct?

A

2-8%

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5
Q

What is reabsorption of water in the collecting duct determined by?

A

Hydration level

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6
Q

How much water is excreted?

A

<1 - 6%

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7
Q

What type of water reabsorption occurs in the PCT and the descending limb of the nephron loop?

A

Bulk reabsorption via leaky epithelia

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8
Q

How much of the total water reabsorption occurs by bulk reabsorption?

A

92% (does not change)

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9
Q

What type of water reabsorption occurs in the collecting duct?

A

Regulated reabsorption via tight epithelia

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10
Q

How much of the total water reabsorption occurs in the collecting duct, what is this regulated by?

A

2-8% - regulated by antidiuretic hormone (ADH)

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11
Q

What are the four places where sodium is reabsorbed in the nephron?

A

PCT, ascending limb on nephron loop, DCT and collecting duct

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12
Q

How much sodium is reabsorbed in the PCT?

A

67%

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13
Q

How much sodium is reabsorbed in the ascending limb of the nephron loop?

A

25%

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14
Q

How much sodium is reabsorbed in the DCT?

A

5%

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15
Q

How much sodium is reabsorbed in the collecting duct?

A

2-3%

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16
Q

How much sodium is excreted?

A

<1%

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17
Q

What type of sodium reabsorption occurs in the PCT and the ascending limb of the nephron loop?

A

Bulk reabsorption via leaky epithelia

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18
Q

How much of the total sodium reabsorption occurs by bulk reabsorption?

A

92%

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19
Q

What type of sodium reabsorption occurs in the DCT and the collecting duct?

A

Regulated reabsorption via tight epithelia

20
Q

How much of the total sodium reabsorption occurs by regulated reabsorption, and what is this regulated by?

A

7-8% - regulated by aldosterone

21
Q

What drives and regulates body water homeostasis?

A

Distribution of water, osmolarity of solutions, chances in osmolarity, reabsorption of water and sodium in nephron and effects of osmotic & volume changes on the kidney

22
Q

What is water reabsorption in the PCT driven by?

A

Na+ reabsorption

23
Q

What transporter transports sodium across the apical membrane?

A

Sodium-glucose cotransporter

24
Q

What is the driving force for the Sodium-glucose cotransporter?

A

Sodium gradient

25
Q

How is chloride attracted across the epithelial cell?

A

The positive charge on the sodium attracts the negative charge on the chloride, allowing it to go down its concentration gradient via the paracellular pathway

26
Q

How does Na+ facilitate water reabsorption?

A

Na+ and Cl- in the peritubular fluid increases the osmolarity, attracting water through aquaporins

27
Q

What do juxtamedullary nephrons cause in the nephron loop?

A

A hyper-osmotic medullary gradient

28
Q

What are changes in ECF osmolarity detected by?

A

Osmoreceptors in the hypothalamus

29
Q

What do the osmoreceptors stilulate?

A

The posterior pituitary gland to secrete more/less ADH

30
Q

What does ADH do?

A

Alters water permeability of the collecting duct cells by delivering/removing aquaporins in the apical membrane of CD cells

31
Q

Explain what happens to water during dehydration

A

Increased osmolarity in ECF, stimulates more ADH secretion for kidneys to increase water reabsorption and increase ECF volume

32
Q

Explain what happens to water during hyper-hydration

A

Decreased osmolarity in ECF, stimulates less ADH secretion for kidneys to decrease water reabsorption and decrease ECF volume

33
Q

What is an increase in ECF volume detected by

A

Cardiac muscle cells (because e.g. increased volume (plasma) means more blood is being pumped into your heart per beat, therefore stretch receptors are stimulated)

34
Q

What do the cardiac muscle cells stimulate?

A

The release of ANP

35
Q

What does ANP do?

A

Acts on kidneys to increase Na+ and water loss in urine to decrease ECF volume

36
Q

What is a decrease in ECF volume detected by?

A

Kidneys

37
Q

What do the kidneys stimulate?

A

Activation of RAAS and an increased release of ADH

38
Q

What does RAAS do?

A

Increases the release of aldosterone from the adrenal gland and therefore the delivery of more sodium channels to the apical membrane

39
Q

What does the increased release of ADH and aldosterone cause?

A

Decreased Na+ and water loss in urine

40
Q

What is found in normal urine?

A

Water, creatinin, urea, uric acid, H+, Na+, medications and toxins

41
Q

What is found in pathological (abnormal) urine?

A

Glucose, protein, blood, haemoglobin, white blood cells and bacteria

42
Q

What does normal urine look like?

A

Clear to light or dark amber (yellow) colours

43
Q

What does pathological (abnormal) urine look like?

A

Orange, red, brown, blue/green colours

44
Q

What could abnormal urine taste like?

A

Sweet from the presence of glucose

45
Q

What would be the cause of ‘fruity’ smelling urine?

A

Ketones from fasting, diabetes, or chronic alcohol abuse

46
Q

What could be the cause of ‘rotten’ smelling urine?

A

Bacterial infection of tumour

HUBS192 2024 (38 decks)

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