GFR, RBF, and clearance Flashcards

1
Q

What is the renal definition of filtration?

A

Movement of ultrafiltrate of plasma into Bowman’s space

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2
Q

What is the general equation for excretion?

A

Excretion = Filtration - reabsorption + secretion

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3
Q

What is the normal volume of glomerular filtration per minute and per day?

A

120 mL/min or 180 L/day

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4
Q

What is the is the filtration fraction?

A

GFR/RPF

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5
Q

What is the equation for GFR?

A

Kf x net filtration pressure

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6
Q

What are the autoregulation mechanisms of renal blood flow?

A

Myogenic response
Tubuloglomerular feedback

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7
Q

What is the myogenic response in renal autoregulation?

A

Stretch receptors activated to cause vasoconstriction

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8
Q

What is the function of the macula dense?

A

Responds to increased Na and Cl levels to trigger tubuloglomerular feedback

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9
Q

What are the two end results of tubuloglomerular feedback?

A

Decreased renin release
Vasoconstriction

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10
Q

What is the direct action of SyNS stimulation in the kidney?

A

Acts on alpha-1 receptors to constrict afferent arterioles, decreasing GFR

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11
Q

What is the mechanism of SyNS constriction of efferent arterioles?

A

SyNS stimulates beta-1 receptors on granular cells to increase renin release; angiotensin II causes efferent vasoconstriction

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12
Q

What stimulates renal prostaglandin synthesis?

A

Increased SyNS
Increased angiotensin II

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13
Q

What is the role of renal prostaglandins?

A

Modulating effect on the vasoconstriction caused by SyNS and angiotensin II

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14
Q

What stimulates release of ANP and BNP?

A

Increased blood volume

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15
Q

What stimulates NP production in the kidney?

A

Increased blood volume
Vasoactive hormones

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16
Q

What is the definition of clearance?

A

Volume of plasma which contains the substance excreted per given time

17
Q

What is the equation for clearance?

A

Cx = (Ux x V)/Px
Excreted = urinary concentration x urine flow

18
Q

What are the properties of inulin in the kidneys?

A

Freely filtered
Not reabsorbed or secreted

19
Q

What are the properties of creatinine in the kidneys?

A

Freely filtered
Not reabsorbed
Slightly secreted

20
Q

What are the properties of PAH in the kidneys?

A

Freely filtered
Actively secreted
Not reabsorbed

21
Q

What is the equation of RBF?

A

RBF = RPF x [1/(1-hematocrit)]

22
Q

What is the equation for net transport?

A

Net transport = filtered load - rate of excretion

23
Q

What is indicated by a positive net transport?

A

Filtered load > rate of excretion
substance is reabsorbed

24
Q

What is indicated by a net transport equal to zero?

A

Substance is freely filtered
It is not reabsorbed or secreted

25
Q

What is indicated by a negative net transport?

A

Rate of excretion > filtered load
Substance is freely filtered and secreted

26
Q

What is likely for a substance whose clearance is higher than the clearance of inulin?

A

Substance is likely freely filtered and secreted

27
Q

What is likely for a substance whose clearance is less than the clearance of inulin?

A

It is likely filtered and partially reabsorbed

28
Q

What does a clearance of 0 indicate about a substance?

A

It is either not filtered, or filtered and entirely absorbed

29
Q

What is indicated about a substance whose clearance is equal to the clearance of PAH?

A

It is filtered and entirely secreted

30
Q

What is the effect of decreased GFR on BUN?

A

BUN will increase

31
Q

What are the properties of BUN in the kidney?

A

Freely filtered
About 50% reabsorbed

32
Q

How is BUN affected by ADH?

A

Increased ADH will increase BUN reabsorption

33
Q

What is the affect on plasma creatinine and BUN if GFR is reduced by half?

A

Both plasma concentrations will double