Bridge to renal physiology

Question 1

Hormones produced by the kidney

Answer 1

Renin
EPO
Calcitriol

Question 2

Average values of GFR per minute and per day

Answer 2

125 ml/min
180 L/day

Question 3

Average urine volume per day

Answer 3

1 L/day

Question 4

Components of filtration coefficient

Answer 4

Total surface area available for filtration
Permeability per unit of surface area

Question 5

Equation of net ultrafiltration (Puf)

Answer 5

Pgf - Pbs - pi gc

Question 6

Equations for GFR

Answer 6

Kf x Puf
Kf [(Pgc-Pbs) - (pi gc - pi bs)]

Question 7

Components of autoregulation/local control of renal blood flow

Answer 7

Myogenic response
Tubuloglomerular feedback

Question 8

Components of systemic/reflex control of renal blood flow

Answer 8

SyNS
Angiotensin II
ANP
Prostaglandins

Question 9

Myogenic response of local control of renal blood flow

Answer 9

Increase stretch triggers Na/K in smooth muscle –> cell depolarizes and Ca channel opens –> Ca binds to calmodulin and muscle contracts –> afferent arteriole constriction –> decreased RBF and limit increase of GFR

Question 10

Brief description of tubuloglomerular feedback in local control of renal blood flow

Answer 10

Increased BP increases GFR –> extraglomerular mesangial cells trigger juxtuglomerular, mesangial, and afferent arteriole smooth muscle cells
-Juxtoglomerular cells decrease renin
-Mesangial cells and afferent smooth muscle cells cause vasoconstriction –> decrease GFR

Question 11

General result of tubuloglomerular feedback control of renal blood flow

Answer 11

Afferent vasoconstriction limits increase GFR
Slight increase in glomerular capillary pressure
No change in efferent arteriole tone
Slight increase in renal blood flow

Question 12

SyNS activity on renal afferent arterioles

Answer 12

Directly on alpha-1 receptors on smooth muscle –> constriction –> decrease GFR

Question 13

SyNS activity on renal efferent arterioles

Answer 13

Acts on beta-1 receptors of granular cells to increase renin –> increase angiotensin II –> constriction of efferent arterioles –> increase GFR

Question 14

Factors that increase renal prostaglandin synthesis

Answer 14

Increased SyNS activity
Increased angiotensin II

In response to low BP

Question 15

Affect of prostaglandin on the kidneys

Answer 15

Modulates efferent constriction from angiotensin II and afferent constriction by SyNS –> overall decrease in RBF with minimal change in GFR

Question 16

What drug class blocks prostaglandin synthesis in the kidneys?

Answer 16

NSAIDs

Question 17

How do NSAIDs affect renal blood flow?

Answer 17

Constriction of both afferent and efferent arterioles, especially in pts with low CO

Question 18

How do ACE inhibitors and ARBs affect renal blood flow?

Answer 18

Decrease angiotensin II –> relaxation of efferent arterioles

Question 19

Affect of NSAID combined with ACE inhibitor or ARB on renal blood flow

Answer 19

Constriction of afferent arterioles and relaxation of efferent arterioles –> severe reduction in GFR

Question 20

Affect of ANP and BNP on renal blood flow

Answer 20

Increase GFR and RBF to increase Na excretion

Question 21

Affect of NO on renal blood flow

Answer 21

Vascular relaxation –> increase GFR and RBF

Question 22

Vasoactive hormones that cause NO release

Answer 22

Acetylcholine
Histamine
Bradykinin
ATP

Question 23

Filtration of BUN in kidneys

Answer 23

Freely filtered and 50% reabsorbed

Question 24

Effect of dehydration on BUN

Answer 24

Increase

Question 25

Effect of decreased GFR on BUN

Answer 25

Increase

Question 26

What will happen to creatinine and BUN values if GFR is reduced by half?

Answer 26

Both with double, ratio generally unchanged

Question 27

Reason by BUN/creatinine ratio increases in dehydration

Answer 27

BUN increases more than creatinine does