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PHGY-210 > Renal - Lecture 4 > Flashcards

Renal - Lecture 4 Flashcards

1
Q

What is osmolarity?

A

total solute concentration of a solution; measure of water concentration in that the higher the solution osmolarity, the lower the water concentration

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2
Q

What is hypoosmotic?

A

having total solute concentration less than that of normal extracellular fluid (300 mOsm)

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3
Q

What is isoosmotic?

A

having total solute concentration equal to that of normal extracellular fluid

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4
Q

What is hyperosmotic?

A

having total solute concentration greater than that of normal extracellular fluid

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5
Q

Water is ___ filtered.

A

freely

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6
Q

How much of water is reabsorbed?

A

99%

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7
Q

Where does the majority of water reabsorption occur?

A

in the proximal tubule

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8
Q

Where does the major hormonal control of reabsorption of water occur?

A

CD

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9
Q

What kind of process is water reabsorption?

A

passive

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10
Q

What is the direction of movement of water in the proximal tubule?

A

tubular lumen -> interstitial fluid

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11
Q

What happens to the osmolarity in the tubular lumen?

A

it decreases

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12
Q

What happens to osmolarity in the interstitial fluid?

A

it increases

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13
Q

Step 1 of water reabsorption:
Na is reabsorbed from the ___ ___ to the ___ ___ across the epithelial cells.

A

tubular lumen
interstitial fluid

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14
Q

Step 2 of water reabsorption:
The local osmolarity in the lumen ___, while the local osmolarity in the interstitium ___.

A

decreases
increases

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15
Q

Step 3 of water reabsorption:
This difference in osmolarity causes net diffusion of water from the ___ into the ___ ___.
via tubular cells’ plasma membranes via ___ ___.

A

lumen
interstitial fluid
tight junctions

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16
Q

Step 4 of water reabsorption:
From the interstitium, water, sodium, and everything else dissolved in the interstitial fluid move together by ___ ___ into ___ ___.

A

bulk flow
peritubular capillaries

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17
Q

When the water intake is small, the kidney reabsorbs ___ water.

A

more

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18
Q

What is the urine output when the kidney reabsorbs more water?

A

0.4 L

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19
Q

When water intake is large, the kidney reabsorbs ___ water.

A

less

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20
Q

What is the urine output when the kidney reabsorbs less water?

A

25 L

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21
Q

Where does the dynamic regulation of water reabsorption occur?

A

collecting duct

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22
Q

What are the 2 critical components of the dynamic regulation of water reabsorption?

A
  1. high osmolarity of the medullary interstitium
  2. permeability of CD to water (regulated by vasopressin)
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23
Q

The kidney has the ability to concentrate urine up to ___.

A

1400 mOsm/L

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24
Q

Urinary concentration takes place as ___ ___ flows through the ___ collecting ducts.

A

tubular fluid
medullary

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25
Q

What does urinary concentration depend on?

A

the hyperosmolarity of the interstitial fluid

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26
Q

In the presence of ___, water diffuses out of the ducts into the interstitial fluid in the medulla to be carried away.

A

vasopressin

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27
Q

The countercurrent multiplier system comes from the anatomical structure of the ___ ___ ___.

A

Loop of Henle

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28
Q

The medullary interstitial fluid becomes hyperosmotic through the function of ___ ___.

A

Henle’s loop

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29
Q

Is the ascending limb thick or thin?

A

thick

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30
Q

What kind of flow is found in the descending and ascending limb?

A

countercurrent

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31
Q

The proximal tubule cells reabsorb Na and water cells ___.

A

proportionally

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32
Q

What is the fluid that leaves the proximal tubule?

A

isoosmotic (300 mOsm)

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33
Q

The thick ascending limb is very active in the reabsorption of ___.

A

NaCl

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34
Q

The thick ascending limb is impermeable to ___.

A

water

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35
Q

Near the ascending limb, the interstitial fluid becomes a bit ___.

A

hyperosmotic

36
Q

In the tubule of the ascending limb, it becomes ___.

A

hypoosmotic

37
Q

The descending limb does not reabsorb ___.

A

NaCl

38
Q

The descending limb is permeable to ___.

A

water

39
Q

In the descending limb, water gets pulled ___, into the ___.

A

away, interstitium

40
Q

The fluid in the descending limb becomes ___.

A

hyperosmotic

41
Q

After the movement of fluid, the osmolarity pattern is:

A

hyperosmotic -> hypoosmotic

42
Q

The interstitial osmolarity is identical to the ___ limb.

A

descending

43
Q

What are vasa recta?

A

blood vessels in the medulla

44
Q

What kind of structure are vasa recta?

A

hairpin-loop

45
Q

What is the function of the vasa recta?

A

it minimizes excessive loss of solute from the interstitium

46
Q

In addition to NaCl, ___ also contributes to medullary osmolarity.

A

urea

47
Q

Water reabsorption depends on the water permeability of the ___.

A

tubules

48
Q

What does the permeability of the epithelium depend on?

A

the tubular segment

49
Q

The proximal tubule has a ___ permeability to water.

A

high

50
Q

What does permeability largely depend on?

A

the presence of water channels in the plasma membrane (aquaporins)

51
Q

Water permeability in the ___ and ___ is subject to physiological control.

A

CCD and MCD

52
Q

What controls the water permeability in the CCD and MCD?

A

vasopressin

53
Q

What kind of hormone is vasopressin?

A

anti-diuretic hormone

54
Q

What is vasopressin produced by?

A

hypothalamic neurons

55
Q

Where is vasopressin released from?

A

posterior lobe of the pituitary gland

56
Q

What 2 receptors does vasopressin bind to?

A

GPCR V1 and V2

57
Q

Where is GPCR V1 found?

A

smooth muscle

58
Q

Where is GPCR V2 found?

A

kidney

59
Q

What does vasopressin stimulate the insertion of in the luminal membrane of the collecting duct cells?

A

aquaporins

60
Q

Where does vasopressin stimulate the insertion of aquaporins?

A

in the luminal membrane of the collecting duct

61
Q

What does vasopressin increase?

A

water permeability

62
Q

When vasopressin is present, collecting ducts become ___ to water —-> water ___

A

permeable
reabsorption

63
Q

When vasopressin is not present, collecting ducts become ___ to water —-> water ___

A

impermeable
diuresis

64
Q

What is diabetes insipidus caused by?

A

malfunction of the vasopressin system (vasopressin does NOT work)

65
Q

What regulates the rate of water reabsorption from the tubules?

A

vasopressin

66
Q

Vasopressin is a major regulator of water___.

A

excretion

67
Q

What are the two mechanisms to regulate vasopressin secretion?

A
  1. Osmoreceptor control (most important)
  2. Baroreceptor control (less sensitive)
68
Q

Excess H20 ingestion causes ___ in H20 excretion.

A

increase

69
Q

What happens to body fluid osmolarity and firing by hypothalamic osmoreceptors when excess H20 is ingested?

A

they decrease

70
Q

What happens to vasopressin secretion when excess H20 is ingested?

A

it decreases

71
Q

What happens to tubular permeability to H20 and H20 reabsorption when excess H20 is ingested?

A

it decreases

72
Q

What happens to venous, atrial and arterial pressures when plasma volume decreases?

A

it decreases

73
Q

What happens to vasopressin secretion when venous, atrial and arterial pressures decrease?

A

they increase

74
Q

What are the reflexes of the vasopressin secretion mediated by when venous, atrial and arterial pressures decrease?

A

cardiovascular baroreceptors

75
Q

What happens to tubular permeability to H20 and H20 reabsorption when plasma vasopressin increases?

A

they increase

76
Q

When plasma volume decreases, H20 excretion ___.

A

decreases

77
Q

What causes us to feel thirsty?

A

the increase in plasma osmolarity

78
Q

What senses an increase in plasma osmolarity and causes thirst?

A

osmoreceptors

79
Q

___ in plasma volume can be sensed by ___ to increase thirst.

A

decrease, baroreceptors

80
Q

What else can cause thirst?

A

dry mouth and throat

81
Q

What can decrease thirst?

A

metering of water intake by GI tract

82
Q

What does severe sweating cause a loss of?

A

hypoosmotic salt solution

83
Q

Loss of hypoosmotic salt solution causes an ___ in plasma volume and ___ in plasma osmolarity during severe sweating.

A

decrease
increase

84
Q

When plasma volume decreases, the GFR ___ and plasma aldosterone ___ during severe sweating.

A

decreases
increases

85
Q

The decrease of GFR and increase in plasma aldosterone cause ___ in sodium excretion during severe sweating.

A

decrease

86
Q

The increase in plasma osmolarity during severe sweating causes an ___ in plasma vasopressin.

A

increase

87
Q

The increase in plasma vasopressin during severe sweating causes a ___ in H20 excretion.

A

decrease

PHGY-210 (36 decks)

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