Renal Circulation

Question 1

Renal plasma flow equation

Answer 1

RPF = RBF x (1-Hct)

Question 2

Filtration fraction equation

Answer 2

FF = GFR/RPF

Question 3

Distribution of blood flow to the kidneys

Answer 3

• most flow through efferent arterioles into the peritubular capillaries of the cortex
• only 5-10% through the medulla

Question 4

What generates filtration in the kidneys? (4)

Answer 4

1. hydraulic pressure in glomerular capillaries
2. renal blood flow rate
3. blood oncotic pressure
4. filtration coefficient

Question 5

What is hydraulic pressure?

Answer 5

pressure resulting from the effects of liquids

Question 6

What are the effects of vasoconstriction on the kidney?

Answer 6

• decreased flow
• increased pressure upstream
• decreased pressure downstream

Question 7

What are the effects of pre- and post-glomerular capillary sphincters?

Answer 7

• increased glomerular capillary pressure leading to formation of filtrate
• decreased peritubular capillary pressure leading to reabsorption of fluid

Question 8

Name 3 factors causing renal constriction

Answer 8

1. sympathetic nervous system (key!)
2. angiotensin II (key!)
3. endothelin

Question 9

Name 5 factors causing renal vasodilation

Answer 9

1. PGE2 (key!)
2. PGI2
3. nitric oxide
4. bradykinin
5. dopamine (key!)

Question 10

What are the effects of sympathetic innervation on the glomeruli?

Answer 10

• sympathetic nerve fibers activate alpha1 receptors on afferent and efferent arterioles
• causes vasoconstriction
• many more alpha1 receptors on afferent arterioles

Question 11

How would SNS activation affect RBF and GFR?
A. decreased RBF and decreased GFR
B. decreased RBF and increased GFR
C. increased RBF and decreased GFR
D. increased RBF and increased GFR

Answer 11

A. decreased RBF and decreased GFR

Question 12

Characteristics of angiotensin II

Answer 12

• potent vasoconstrictor
• affects both afferent and efferent arterioles
• greater effect on efferent arteriole

Question 13

How would angiotensin II affect RBF and GFR?
A. decreased RBF and decreased GFR
B. decreased RBF and increased GFR
C. increased RBF and decreased GFR
D. increased RBF and increased GFR

Answer 13

B. decreased RBF and increased GFR

Question 14

What are the effects of low levels of angiotensin II on the kidney?

Answer 14

• both AA and EA constrict

- EA constricts more, increased pressure in glomerular capillaries and increased GFR

Question 15

What are the effects of high levels of angiotensin II on the kidney?

Answer 15

• both AA and EA constrict

- AA constricts more, decreased pressure in glomerular capillaries and decreased GFR

Question 16

What do prostaglandins do in the kidney?

Answer 16

vasodilate both afferent and efferent arterioles

Question 17

What are the effects of low levels of dopamine on the kidney?

Answer 17

dilates renal arterioles

Question 18

What are the effects of high levels of dopamine on the kidney?

Answer 18

vasoconstricts renal arterioles

Question 19

What is autoregulation?

Answer 19

• protects kidney function from large and abrupt changes in systemic BP
• protects glomerulus from systemic pressure

Question 20

What are the two theories explaining auto regulation

Answer 20

• myogenic (stretch of arteriolar wall causes opening of smooth muscle Ca2+ channels leading to vasoconstriction)
• tubuloglomerular feedback

Question 21

When does nephrotoxicity from NSAIDs occur?

Answer 21

• accidental overdosage

- as a risk factor with other causes for attention (like volume depletion)

Question 22

Why is the kidney at risk for nephrotoxicity?

Answer 22

• high blood flow
• high metabolic rate
• reabsorption/secretion of toxic substances
• poor blood flow
• concentration of toxins