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Urology and Renal Medicine > Regulation of Sodium > Flashcards

Regulation of Sodium Flashcards

1
Q

most prevalent solute in the ECF?

A

sodium

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2
Q

describe the association between sodium and water retention

A

increased sodium intake increases water retention

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3
Q

describe the link between dietary sodium and blood pressure

A

^ Na+ > ^ osmolarity > ^ water intake + retention > ^ ECF volume > ^ blood volume and BP
(and vice versa)

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4
Q

what mechanisms are there for regulating sodium intake?

A

central

peripheral

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5
Q

central mechanism depends on what part of the brain?

A

lateral parabroachial nucleus

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6
Q

In euvolemia, is Na+ intake stimulated or inhibited?

A

inhibited

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7
Q

Na+ intake is inhibited by what molecules?

A

serotonin

glutamate

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8
Q

In the sodium deprived state, appetite for sodium is increased via what?

A

GABA

opioids

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9
Q

Peripheral mechanisms for controlling Na+ intake are based on?

A

taste

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10
Q

where is the majority of Na+ reabsorbed in the nephron?

A

proximal convoluted tubule

next is loop of Henle from countercurrent mechanism

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11
Q

how is Na+ reabsorbed in the nephron?

A

co transport

counter transport with glucose, amino acids, bicarbonate

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12
Q

what % of Na+ in the tubular fluid ends up being excreted?

A

1%

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13
Q

what is GFR?

A

glomerular filtration rate

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14
Q

what % of renal plasma enters the tubular system?

A

20

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15
Q

equation linking GFR and RPF

A

GFR = RPF x 0.2

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16
Q

What happens to Na+ reabsorption if GFR increases?

A

flow rate in the PCT and the LOH will increase, the amount sodium reabsorbed increases

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17
Q

Maximum rate of Na+ reabsorption is dependent on?

A

transporters present and the flow

18
Q

The distal convoluted tubule is separated from the glomerulus by?

A

extraglomerular mesangial cells and juxtaglomerular cells

19
Q

As more Na/Cl is delivered to the distal convoluted tubule, the amount of sodium and chloride transported by the cells of the _________ increases.

A

macula densa

20
Q

Above a threshold value, macula densa cells start to release?

A

adenosine

ATP

21
Q

Adenosine and ATP release activate receptors to have what two effects?

A

reduction of renin production

stimulation of contraction of smooth muscle cells of the afferent arteriole

22
Q

Contraction of smooth muscle in afferent arteriole leads to what?

A

reduction in RPF

reduction in perfusion pressure

23
Q

how to reduce Na+ excretion?

A

reduce glomerular filtration by constricting the afferent arteriole more than the efferent arteriole or relaxing the efferent arteriole more than the afferent arteriole

24
Q

Sympathetic stimulation reduces sodium loss via contraction of afferent and efferent arterioles and by what other mechanism?

A

increases uptake of Na+ by PCT cells, increasing the activity of the sodium proton exchanger

25
Q

Mechanisms to increase Na+ uptake in the nephron are opposed by the activity of what?

A

atrial naturietic peptide

26
Q

Action of atrial naturietic peptide on the nephron

A

promotes dilation of of afferent arteriole
inhibits renin release
reduces uptake of Na+ in PCT, DCT, CD

27
Q

Overall, if blood volume falls or sodium levels are low and we need to promote sodium retention we see:

A 
increased sympathetic activity
increased renin production > increased angiotensin II
increased NaCl reabsorption 
vasocontriction
release of aldosterone
28
Q

Is aldosterone a steroid or peptide hormone?

A

steroid

29
Q

where is aldosterone synthesised?

A

adrenal gland
cortex
zona glomerulosa

30
Q

aldosterone is release in response to?

A

angiotensin II

decrease in blood pressure

31
Q

what enzyme is required for the last 2 steps of aldosterone synthesis?

A

aldosterone synthetase

32
Q

Aldosterone in excess leads to?

A

hypokalaemic alkalosis

33
Q

Aldosterone stimulates?

A

increased Na+ reabsorption
increased K+ secretion
increased H+ secretion

34
Q

aldosterone binds to what type of receptor?

A

mineralocorticoid

35
Q

on aldosterone binding what occurs?

A

monomer loses association to HSP90
dimerises
translocates to the nucleus > binds to DNA promoter region > stimulates expression of target genes

36
Q

target genes of aldosterone?

A

ENaC (epithelial sodium channel)

Na+/K+ ATPase and sets of regulatory proteins

37
Q 
Are the following permeable or impermeable to Na+?
descending loop of Henle
ascending loop of Henle 
DCT
CD
A

impermeable
permeable
permeable
permeable in the presence of aldosterone

38
Q

symptoms of hypoaldosteronism

A

dizziness
low blood pressure
salt craving
palpitations

39
Q

symptoms of hyperaldosteronism

A

high blood pressure
muscle weakness
polyuria
thirst

40
Q

Liddle’s syndrome

A

normal to low levels of aldosterone
same phenotype as hyperaldosteronism
genetic disease
mutations to the aldosterone activated sodium channel

Urology and Renal Medicine (8 decks)

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