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Physiology I Exam 2 > Lecture 7: Regulation of Sodium Balance > Flashcards

Lecture 7: Regulation of Sodium Balance Flashcards

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1
Q

What solute determines ECF volume (which in turn determines plasma volume, blood volume, and blood pressure)?

A

Sodium

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2
Q

Na+ excretion in comparison to Na+ intake

A

Must be equal

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3
Q

Positive Na balance

A

Na excretion less than intake (leads to ECF volume expansion and high blood pressure)

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4
Q

Negative Na balance

A

Na excretion greater than intake (Blood pressure decreases)

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5
Q

Na content definition

A

Absolute amount

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6
Q

Na concentration definition

A

Determined by amount of Na+ volume water

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7
Q

Na is usually expressed as

A

Concentration

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8
Q

Na is _________ and _______ throughout the nephron

A

Freely filtered and reabsorbed

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9
Q

Most Na+ reabsorption occurs in the

A

Proximal convoluted tubule

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10
Q

Water reabsorption is linked to what?

A

Na+ reabsorption in the PCT

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11
Q

How much filtered Na+ does the thick ascending limb reabsorb?

A

25%

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12
Q

What is special about the thick ascending limb?

A

Impermeable to water

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13
Q

Distal tubule and collecting ducts reabsorb how much filtered Na+?

A

8%

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14
Q

Where does fine tuning of sodium reabsorption and aldosterone occur?

A

Distal tubule and collecting ducts

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15
Q

What is the mechanism for Na+ reabsorption in the Early PCT?

A

Sodium (Na) absorbed mostly with bicarb, glucose, AA

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16
Q

What is the mechanism for Na+ reabsorption in the Late PCT?

A

Na absorbed mostly with Cl

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17
Q

How much filtered Na does the PCT reabsorb?

A

67%

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18
Q

How much filtered water does the PCT reabsorb?

A

67%

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19
Q

What is the term for when Na+ and water are reabsorbed together?

A

Isosmotic reabsorption

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20
Q

Where is the site for glomerulotubular balance?

A

PCT

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21
Q

Glomerulotubular balance definition

A

Major regulatory mechanism in PCT to ensure that a constant fraction of filtered load is reabsorbed, regardless of GFR

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22
Q

Where is the highest priority reabsorptive work done?

A

Early PCT

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23
Q

What solutes are considered highest priority reabsorptive work?

A

Na+, glucose, amino acids, HCO3-

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24
Q

Transport from the luminal membrane method is mostly

A

Secondary transport

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25
Name the counter transport method for the luminal membrane into the cell in the early PCT
Angiotensin 2
26
How much filtered glucose and AA are reabsorbed by the mid-PCT?
100% filtered glucose and AA
27
What % HCO3 reabsorbed by mid-PCT?
85%
28
Fanconi Syndrome is
A kidney tubule disorder
29
Cystinosis
Accumulation of AA cystine within cells --> Crystals
30
Cystinuria
Persistent kidney stones caused by increased cystine in urine
31
How is Fanconi Sydrome diagnosed?
Increased level of acid in blood And glucose, AA, phosphate in the urine
32
What is fluid entering the late PCT high in?
Cl-
33
NaCl is absorbed where?
Late PCT
34
What drives NaCl absorption in the late PCT?
High tubular fluid (TF) Cl concentration
35
Name the two routes for NaCl absorption in late PCT
Paracellular and cellular
36
Cellular route methods (2)
Na+/H+ exchanger (luminal) Cl-/formate-change (luminal)
37
Paracellular route definition
Tight junctions loose and permeable to small solutes
38
Paracellular route explanation
Cl- diffuses, followed by Na+
39
What is coupled in proportion in the PCT?
Solute and water reabsorption
40
What is the primary event of isosmotic reabsorption of Na and water in PCT?
Solute reabsorption (water follows passively)
41
Reabsorption of isosmotic fluid is dependent on what?
High oncotic pressure in peritubular capillaries
42
What transport system removes Na+ from the cell in the PCT?
Na+/K+ ATPase
43
Glomerulotubular mechanism
If filtration fraction increases, then oncotic pressure in peritubular capillaries increases, thus reabsorption increases
44
Increased GFR means higher volume of what?
Ultrafiltrate
45
Glomerulotubular balance results in what?
Most concentrated blood in efferent arteriole
46
What will influence tubular reabsorption and over-ride glomerulotubular balance?
Changes in ECF volume
47
Volume expansion causes a decrease in what in PCT?
Fractional reabsorption
48
If ECF volume is increased, then what pressure decreases?
Peritubular capillary oncotic pressure
49
A decrease in peritubular capillary oncotic pressure causes what to increase?
Capillary fluid pressure
50
Volume contraction causes an increase in what in PCT?
Fraction reabsorption
51
What is also activated to low blood volume and BP?
RAAS
52
During volume contraction, what increases due to ECF volume decreasing?
Capillary oncotic pressure
53
What decreases due to capillary oncotic pressure increasing?
Capillary fluid pressure
54
What does the decrease in capillary fluid pressure lead to?
Increase in fractional reabsorption by peritubular capillaries
55
Thin descending limb is permeable to what
Reabsorption of water and secretion of small solutes (NaCl and urea)
56
What happens in the thin descending limb?
What moves out and small solutes move in, the TF becomes hyper-osmotic
57
Thin ascending limb is permeable to
Reabsorption of NaCl
58
What thin ascending limb impermeable to?
Reabsorption of water
59
What happens in the thin ascending limb?
Solutes move out, so the TF becomes hypo-osmotic (Because water stays)
60
How much filtered Na is reabsorbed by the thick ascending limb?
~25%
61
What co-transporters pull Na from lumen to cell of thick ascending limb?
Na+/2Cl/K+ co-transporters
62
Where is the site of action for many loop diuretics (furosemide)?
Thick ascending limb
63
Thick ascending is special because it is
Impermeable to water, water cannot follow NaCl here
64
How does furosemide act?
Acts on anion in Na+/2Cl/K+ co-transporter, binds to Cl- portion and blocks its action
65
What parts make up the terminal nephron?
Collecting ducts and distal tubule
66
How much filtered Na+ is reabsorbed in the distal tubule and collecting ducts?
8%
67
How much filtered Na+ is reabsorbed through the early DT?
~5%
68
What co-transporter does the early DT use?
Na+/Cl- co-transporter
69
What are the two major cell types in the late DT and collecting duct?
Principle cells Alpha intercalated cells
70
What are principal cells?
Responsible for Na reabsorption if that occurs, K secretion, water absorption
71
What are alpha intercalated cells responsible for?
K absorption and H secretion
72
How much Na is reabsorbed by the Late DT and collecting Duct?
3% (fine-tuning of final Na+ excretion)
73
Principal cells use what transport method for Na?
Na+ channels and diffusion (NOT co-transport)
74
Where is Na+ absorption hormonally regulated?
Principle cells of late DT and CT
75
How does aldosterone increase Na+ reabsorption?
Via increase in number of Na channels and activity of Na+/+ ATPase
76
What is Na+ reabsorption inhibited by?
K+ sparing diuretics
77
Spironolactone
Inhibits aldosterone effects --> Prevents aldosterone from enteringcell

Physiology I Exam 2 (12 decks)

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