Urine Formation By the Kidney

Question 1

What are the normal values of GFR?

Answer 1

125 ml/min
180 L/day

Question 2

What is the normal GFR in newborns?

Answer 2

20 ml/min

Question 3

Compare GFR as a young adult to an elderly person.

Answer 3

GFR declines after 45-50, and is typically lower at age 80 than at age 21 (declines at a rate of about 1ml/min per year)

Question 4

What is Filtration fraction?

Answer 4

proportion of renal plasma that is filtered.

Question 5

Formula for FF?

Answer 5

FF = GFR/RPF (for given amount like gm or mg

Question 6

Filtered load (amount filtered) formula.

Answer 6

GFR x Px (concentration in plasma)

Question 7

Formula for P gradient across renal vasculature.

Answer 7

Renal artery P (systemic arterial P - 100 mmHg) -renal vein P (3-4mmHG)

Question 8

Formula for RBF.

Answer 8

RBF = ΔP / RT

Question 9

What is total renal vascular resistance?

Answer 9

sum of ind. resistance of all vascular components of nephron.

Question 10

What is the formula for RBF?

Answer 10

-RBF = RPF/ (1-Htc)

Question 11

Describe overall action of extrinsic control of kidney.

Answer 11

Effects of the SNS and humoral agents on afferent and/or efferent-arteriolar diameter, glomerular capillary P (πgc) and RBF/RPF

Question 12

RBF and GFR cortical nephrons remain relatively constant in response to changes in mean arterial pressure between what values?

Answer 12

85 - 200 mmHG

Question 13

Be able to reproduce this chart on the mechanisms of myogenic auto regulation.

Answer 13

Reproduce chart

Question 14

What is the tubuloglomerular feedback mechanism?

Answer 14

Selective control of the renal arteriolar resistance in response to changes in distal tubular fluid and solutes flow and NaCl content in the macula densa cells of the JGA

Question 15

Be able to go through the steps of how the tubuloglomerular feedback mechanism works.

Answer 15

Question 16

What do the MD cells produce which attenuates the TG feedback?

Answer 16

NO

Question 17

Summarize steps in TG feedback mechanism.

Answer 17

1. ↑ GFR → ↑ production and release of adenosine and ATP by MD cells
2. Constriction of aff arterioles (direct effect of adenosine and ATP)
   ↓ Renin release by granular cells → ↓ ATII → dilation of eff arterioles
3. ↓ glomerular hydrostatic P & GFR

Question 18

Describe the effects of sympathetic activation on renal hemodynamics. Create flow diagram.

Answer 18

Question 19

How do low levels of AT II act on efferent arterioles?

Answer 19

constriction

Question 20

How do high levels of AT II act on arterioles?

Answer 20

constriction of both afferent and efferent arterioles

Question 21

How does ADH affect plasma concentration?

Answer 21

very high plasma concentrations

Question 22

How does adenosine affect afferent and efferent arterioles?

Answer 22

afferent constriction
efferent dilation

Question 23

How does thromboxane, leukotrienes and endothelin affect renal system?

Answer 23

(vasoconstriction in renal diseases like acute renal failure, chronic uremia and toxemia of pregnancy because of release of vasoconstrictor like endothelin!!)

Question 24

Prostaglandins PGE2 and PGI2 affect the afferent and efferent arterioles in what way?

Answer 24

cause vasodilation of both afferent and efferent arterioles

Question 25

PG’s can modulate vasoconstriction produced by SNS and ATII. What effect can this have?

Answer 25

prevention of excessive decrease in RBF and GFR

Question 26

How does ANP affect renal arterioles?

Answer 26

dilation of the afferent arterioles but constriction of the efferent arterioles

Question 27

Endothelium derived NO affects renal performance how?

Answer 27

↓ renal vascular resistance and ↑ GFR