Clearance, Rbf, Gfr

Front 1

Superficial nephrons have glomeruli in _________ while juxtamedullary nephrons have glomeruli in __________________.

Back 1

cortex; near junction of cortex and medulla

Front 2

What secretes renin?

Back 2

Juxtaglomerular cells (of afferent arteriole)

Front 3

What is the special region of distal tubule that is part of juxtaglomerular apparatus?

Back 3

macula dense

Front 4

What is clearance equation?

Back 4

Cx = [U]x * V / [P]x

Clearance of X = (Urine concentration of X)*Urine flow rate / (Plasma concentration of X)

Front 5

If a substance is filtered and secreted, does it have a high or low clearance?

Back 5

HIGH

Front 6

Substances that are perfectly filtered are what? An example?

Back 6

They're glomerular markers for GFR. Example is INULIN

Front 7

Clearance ratio (aka fractional excretion)

Back 7

Cx/C_inulin

Gives info about how kidney handles substance X.

Front 8

What does it mean if Clearance ratio is 1?

Back 8

Substance is also a glomerular marker

Front 9

What does it mean if Clearance ratio is > 1?

Back 9

Substance is filtered AND secreted

Front 10

What does it mean if Clearance ratio is < 1?

Back 10

Substance is either not freely filtered, or gets reabsorbed after it's filtered.

Front 11

What is the myogenic hypothesis?

Back 11

Stretching blood vessels (from increase in Pa) causes them to contract, leading to increased resistance.

The increased resistance prevents an increase in blood flow that would have occurred otherwise in response to increased Pa.

In the kidneys, it's the AFFERENT arterioles that constrict.

Front 12

What is tubuloglomerular feedback?

Back 12

When Pa increases, RBF and GFR transiently increase. This causes increased delivery of materials to juxtaglomerular apparatus (sensed by macula densa) which then causes increase in resistance of afferent arteriole.

As a result, RBF and GFR go down.

This is unique to kidney.

Front 13

Does increasing Arterial blood pressure cause an increase in RBF and GFR?

Back 13

No, because of the tubuloglomerular feedback and myogenic mechanism

Front 14

What is the vasoactive substance that the macula densa secretes that causes the afferent arteriole to contract?

Back 14

probably adenosine, which is strange, because in other parts of the body it's a vasodilator.

Front 15

True/false: Renin causes afferent arteriole to constrict via tubuloglomerular feedback

Back 15

FALSE. it's probably adenosine

Front 16

Renal Plasma Flow is to Renal Blood Flow as Plasma is to ______

Back 16

Whole Blood. Plasma is the fluid part of blood.

Front 17

calculation of fractional volume of blood occupied by plasma:

Back 17

1 - hematocrit

Front 18

What is the substance used to measure RPF?

Back 18

Paraaminohippuric acid (PAH)

Front 19

Equation for <b>True RPF</b>:

Back 19

([U]_PAH * V) / ([RA]_PAH - [RV]_PAH)

Front 20

Equation for <b>Effective RPF</b>:

Back 20

Same as the Clearance.
([U]_PAH * V) / ([P]_PAH)

Front 21

Renal Blood Flow (RBF) Equation:

Back 21

RBF = RPF/ (1-Hct)

Front 22

What are the three layers of the glomerular capillary barrier?

Back 22

1) Endothelial cell layer with filtration pores
2) basement membrane
3) Epithelial layer with podocytes interspersed with filtration slits

Front 23

What is the sieving coefficient?

Back 23

Expresses ability of particular solute to make it thru filtration pores. A sieving coefficient of 1 means it is freely filtered, no restriction.

Front 24

What does a low sieving coefficient mean?

Back 24

The substance is not freely filtered. The lower the coefficient, the more restriction there is.

Front 25

What determines GFR?

Back 25

Starling forces. Hydrostatic and oncotic pressures.

Front 26

What are the Starling forces of the kidney?

Back 26

Pgc (capillary hydrostatic pressure), Pbs (Fluid of Bowman's space hydrostatic pressure), PIgc (capillary oncotic pressure)

Front 27

Net ultrafiltration always favors _________________

Back 27

filtration

Front 28

What is the effect of<b> constriction of afferent arteriole</b> on the following:
1) RBF
2) GFR
3) Filtration fraction (GFR/RBF)

Back 28

1) Decreases
2) Decreases
3) Same

Front 29

What is the effect of<b> constriction of efferent arteriole</b> on the following:
1) RBF
2) GFR
3) Filtration fraction (GFR/RBF)

Back 29

1) Decreases
2) Increases (bottleneck effect keeps it around longer)
3) Increases

Front 30

What is the effect of<b> increased plasma protein concentration </b> on the following:
1) RBF
2) GFR
3) Filtration fraction (GFR/RBF)

Back 30

Increased plasma protein concentration increases Capillary Oncotic Pressure (pulling fluid in)
1) No change
2) Decreases
3) Decreases

Front 31

What is the effect of<b> decreased plasma protein concentration</b> on the following:
1) RBF
2) GFR
3) Filtration fraction (GFR/RBF)

Back 31

Decreased plasma [protein] decreases the force pulling fluid in (capillary oncotic pressure).

1) No change
2) Increases (less forces opposing)
3) Increases

Front 32

What is the effect of<b> constriction of the ureter </b> on the following:
1) RBF
2) GFR
3) Filtration fraction (GFR/RBF)

Back 32

There will be an increase in hydrostatic pressure of Bowman's space (Pbs) which opposes filtration.
1) No change
2) Decreases
3) Decreases

Front 33

What is the effect of<b> simultaneous constriction of afferent and efferent arterioles </b> on the following:
1) RBF
2) GFR
3) Filtration fraction (GFR/RBF)

Back 33

Overall effect depends on which one constricts more.

Front 34

What is the effect of<b> Sympathetic nervous system </b> on the following:
1) RBF
2) GFR
3) Filtration fraction (GFR/RBF)

How does it affect these?

Back 34

Sympathetic NS constricts the afferent and efferent arterioles.

1) Decreases
2) Decreases
3) Decreases

Front 35

Are there more alpha receptors on the afferent or efferent arteriole? What are implications of this?

Back 35

More on afferent. It means the sympathetic NS constricts the afferent arterioles more than efferent.

Front 36

What is the effect of<b> Angiotension II</b> on the following:
1) RBF
2) GFR

Back 36

AII preferentially constricts efferent arterioles. This is very important because it can preserve GFR under conditions where GFR would otherwise be compromised.

1) Decreases
2) Increases or maintains

Front 37

What is the effect of<b>ANP </b> on the following:
1) RBF
2) GFR

How does it work on afferent and efferent arterioles?

Back 37

Causes dilation of afferent and constriction of efferent

1) Increases
2) Increases

Front 38

What is the effect of<b> Nitric oxide (NO)</b> on the following:
1) RBF

Back 38

Dilates afferent and efferent.

Increases RBF

Front 39

What is the effect of<b> prostaglandins</b> on the following:
1) RBF
2) GFR
3) Afferent Arterioles
4) Efferent Arterioles

Back 39

1) Protects
2) Protects
3) Preferentially dilates afferents
3) Dilates efferents a little bit

Front 40

What is the effect of<b> Dopamine (low dose)</b> on the following:
1) Afferent Arterioles
2) Efferent Arterioles

Back 40

Dilates BOTH

Front 41

How do you calculate filtration fraction?

Back 41

GFR/RPF

Front 42

How do you measure GFR (ideally)?

Back 42

It's the clearance of inulin

[U]inulin*V / [P]inulin

Front 43

How do you measure GFR (realistically)?

Back 43

Serum creatinine, Blood urea nitrogen. Both of these are normally filtered and NOT reabsorbed (aka excreted).

Front 44

What happens to creatinine if GFR decreases?

Back 44

It isn't excreted and filtered as well, and blood concentrations increase.

Front 45

Why will a substance that is only filtered (but completely) have a mid-range clearance?

Back 45

Only about 20% of the RPF will be filtered. Every time an amount of inulin goes thru the kidney, 80% of it will still remain. Eg., it isn't excreted thru the peritubular capillaries.

Front 46

What is a normal filtration fraction?

Back 46

Clearance of inulin / Clearance of PAH = about 0.20