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Physiology I Exam 2 > Lecture 3: Renal Blood Flow > Flashcards

Lecture 3: Renal Blood Flow Flashcards

1
Q

What % of cardiac output do the kidneys receive?

A

25%

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2
Q

What % of blood in cortex?

A

93%

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3
Q

What % of blood in outer medulla?

A

6%

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4
Q

What % of blood in inner medulla?

A

1%

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5
Q

RBF is directly proportional to what?

A

Pressure gradient between renal artery and renal vein

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6
Q

RBF inversely proportional to resistance of

A

Renal vasculature (mainly the arterioles)

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7
Q

What is the major mechanism for changing renal blood flow?

A

Changing arteriolar resistance, which changes filtration in the kidney

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8
Q

Vasoconstriction does what to GFR in afferent arterioles?

A

Decreases GFR

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9
Q

Vasoconstriction does what to GFR in efferent arterioles?

A

Increases GFR

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10
Q

Sympathetic nervous system and circulating catecholamines have what receptors?

A

Alpha 1

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11
Q

Alpha 1 receptors are more abundant on what part of the glomerulus?

A

Afferent arterioles

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12
Q

If there is an increase in SNS activity, what happens?

A

Decrease both RBF and GFR

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13
Q

Angiotensin 2 is a

A

Renal vasoconstrictor

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14
Q

Angiotensin 2 affects

A

Both afferent and efferent arterioles

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15
Q

Which part of glomerulus is more sensitive to angiotensin 2?

A

Efferent arterioles

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16
Q

What happens with low levels of angiotensin 2 in the kidneys?

A

Increase GFR because main effect is on efferent

17
Q

What happens with high levels of angiotensin 2?

A

Decrease GFR and RBF because both afferent and efferent constricted

18
Q

Dominant effect of atrial natriuretic peptide (ANP)

A

Dilation of afferent arterioles

19
Q

Effect of atrial natriuretic peptide (ANP) on efferent arterioles

A

Constriction

20
Q

What happens when ANP is affecting the glomerulus?

A

Vascular resistance decreases, RBF and GFR increase

21
Q

Where do Prostaglandins E2 and I2 get produced and where do they act?

A

Produced locally in the kidneys and act locally

22
Q

What do Prostaglandins E2 and I2 do when effecting the glomerulus?

A

Vasodilation of afferent and efferent arterioles

23
Q

What do Prostaglandins E2 and I2 act in opposition to?

A

SNS

24
Q

Why do Prostaglandins E2 and I2 vasodilate (what are they trying to prevent)

A

Trying to protect RBF and protect from renal failure due to vasoconstriction caused by SNS

25
Q

What effect does dopamine have on kidney?

A

Dilates renal arterioles

26
Q

What condition is dopamine particularly useful in?

A

Hemorrhage

27
Q

How does Dopamine protect?

A

Vasodilates to counteract SNS vasoconstriction

28
Q

Renal arterial pressure can vary from

A

80 - 200 mm Hg

29
Q

How is RBF maintained within the large range that renal arterial pressure can vary from?

A
  1. Vary to resistance of arterioles - more control of afferent arterioles
  2. RBF only decreases when renal arterial pressure falls below 80 mm Hg
30
Q

What are the two theories of autoregulation?

A
  1. Myogenic hypothesis
  2. Tubuloglomerular feedback hypothesis of autoregulation
31
Q

Explain the myogenic hypothesis

A

Increased arterial pressure stretches blood vessels, which causes reflex contraction of smooth muscle in blood vessel walls, which increases resistance to RBF

32
Q

How does the myogenic hypothesis maintain RBF?

A

The increase in arterial pressure is balanced by the increase in resistance of the afferent arteriole, so RBF remains relatively constant (NOT through autonomic nervous system)

33
Q

Explain tubuloglomerular feedback steps

A
  1. Renal arterial pressure increases
  2. Both RBF and GFR increase
  3. Increase in GFR delivers more solutes and water to macula densa region of early distal tubule
  4. Macula densa senses increased load and responds by secreting vasoactive substance to constrict afferent arteriole
  5. RBF and GFR return to normal
34
Q

Reasons PAH is gold standard to measure RPF

A
  1. Removed only by the kidneys
  2. Both filtered and secreted into proximal tubule
  3. Doesn’t alter RPF
  4. Not synthesized or degraded by kidneys
  5. Almost all PAH enters urine
35
Q

Difference between measuring true and effective RPF?

A

Effective is more practical than True RPF

Physiology I Exam 2 (12 decks)

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