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Physiology Block 4- Renal Physiology > Regulation of Renal Blood Flow > Flashcards

Regulation of Renal Blood Flow Flashcards

1
Q

How does chronic renal failure affect glomerular filtration rate?

A

Reduction in GFR

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2
Q

How does afferent arteriole constriction affect glomerular filtration rate?

A

Decreases hydrostatic glomerular capillary forces, increasing MABP and resistance, which decreases GFR

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3
Q

How does afferent arteriole dilation affect GFR?

A

Increases hydrostatic glomerular capillary forces and decreases MABP, which increases GFR

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4
Q

What is the normal rate of renal blood flow in mL/min/g?

A

4 mL/min/g

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5
Q

Approximately what percent of LV output does the kidney receive?

A

~20%

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6
Q

What is renal fraction? What is the normal value?

A

The ratio between renal blood flow with respect to total cardiac output; 20%

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7
Q

How is renal plasma flow calculated? What is the normal value?

A

RPF= RBF x (1-hemocrit); 600 mL/min

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8
Q

What is the filtration fraction? How is it calculated?

A

Expresses how much of the plasma that enters the kidney per minute is actually filtered into Bowman’s space; FF= GFR/RPF

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9
Q

What is the normal value of filtration fraction?

A

20%

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10
Q

What is the normal rate of urine flow in mL/kg/hr?

A

1 mL/ kg body weight/ hr

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11
Q

How can the amount of fluid reabsorbed be calculated?

A

GFR minus urine V

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12
Q

Relative to other organs, what is the oxygen consumption of the kidneys?

A

Second highest oxygen consumption next to the heart

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13
Q

True or False: Oxygen is a critical factor for regulating renal blood flow?

A

False

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14
Q

What is the relationship between renal oxygen consumption and Na+ reabsorption?

A

Direct, linear, parallel relationship

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15
Q

True or False: Renal arterial-venous PO2 difference is small

A

True

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16
Q

Where in the renal circulatory system are the two largest drops in blood pressure seen?

A

Renal a. to glomerular capillary; Glomerular capillary to tubular capillary

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17
Q

How does increasing the resistance in the afferent arteriole affect glomerular capillary pressure, glomerular filtration rate and renal blood flow?

A

Decreased glomerular capillary pressure, decreased glomerular filtration rate, and decreased renal blood flow

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18
Q

How does increasing the resistance in the efferent arteriole affect glomerular capillary pressure, glomerular filtration rate and renal blood flow?

A

Increased glomerular capillary pressure, increased glomerular filtration rate, and decreased renal blood flow

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19
Q

How does decreasing the resistance in the afferent arteriole affect glomerular capillary pressure, glomerular filtration rate and renal blood flow?

A

Increased glomerular capillary pressure, increased glomerular filtration rate, and increased renal blood flow

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20
Q

How does decreasing the resistance in the efferent arteriole affect glomerular capillary pressure, glomerular filtration rate and renal blood flow?

A

Decreased glomerular capillary pressure, decreased glomerular filtration rate, and increased renal blood flow

21
Q

What are the two mechanisms of intrinsic regulation of renal blood flow?

A

Myogenic mechanism, and tubuloglomerular feedback mechanism

22
Q

What is the goal of renal blood flow autoregulation?

A

Maintenance of constant RBF and GFR

23
Q

True or False: Renal Autoregulation of Blood flow only occurs in a narrow range around set MABP?

A

False- wide range from 90-180 mmHg

24
Q

What is the exclusive mechanism of autoregulation of renal blood flow

A

Changing afferent arteriole resistance

25
Q

Blood pressures below what value will result in decreased GFR?

A

Below 90 mmHg

26
Q

What is the myogenic mechanism of intrinsic renal regulation?

A

It is an intrinsic property of arterial vascular smooth muscle cells where physical stretching (as with increased BP) opens ion channels that allow calcium influx, which causes VSM contraction, increasing vascular resistance

27
Q

True or False: The myogenic mechanism is sufficient to autoregulate renal blood flow?

A

False

28
Q

What is the tubuloglomerular feedback mechanism?

A

A sudden increase in GFR increases the flow of ultrafiltrate, which is sensed by macula densa cells, who respond by releasing ATP and adenosine. These paracrine substances bind to VSM cells in the afferent arteriole of the same nephron and stimulates contraction

29
Q

True or False: Autoregulation of RBF and GFR can be overriden by SNS and hormonal stimulation

A

True

30
Q

How does sympathetic stimulation affect renal blood flow and GFR?

A

SNS stimulation affects afferent and efferent arteriole resistance, decreasing RBF and GFR

31
Q

How does ADH regulate renal blood flow and glomerular filtration rate?

A

ADH binds to V1 receptors on VSM, causing vasoconstriction of afferent and efferent arterioles, decreasing renal blood flow and glomerular filtration rate

32
Q

Where are atrial- and brain- natriuretic peptides synthesized? What are the stimuli that result in their release?

A

ANP is synthesized in the cardiac atria, BNP by the ventricles; Atrial distension, increased plasma volume, and severe volume expansion all stimulate secretion

33
Q

What is the rate-limiting step in Angiotensin II formation?

A

Renin

34
Q

What cells of the kidney produce renin?

A

Juxtaglomerular cells

35
Q

True or False: Angiotensin has some function, but not as much as angiotensin II

A

False- I has no function

36
Q

Where is angiotensin I converted to angiotensin II? By what enzyme?

A

Angiotensin-converting enzyme in the lungs

37
Q

What are the effects of angiotensin II on the kidney? Adrenal gland? Vasculature?

A

Kideny- Na+ retention and fibrosis; Adrenal- aldosterone release; Vasculature- Vasoconstriction and hypertrophy

38
Q

What are the effects of angiotensin II on the brain? On the heart?

A

Brain- stimulates thirst, salt appetite, sympathetic activation and ADH release; Heart- stimulates contractility (inotropy), chronotropy (HR), hypertrophy and fibrosis

39
Q

What is the effect of angiotensin II on renal blood flow and GFR?

A

Decrease in RBF and GFR

40
Q

What are the effects of angiotensin II on mesangial cells?

A

Decreased Kf (surface area filtration) and decreased glomerular filtration rate

41
Q

What is the most powerful and longest lasting vasoconstrictor in the body?

A

Endothelin

42
Q

What kidney cells produce endothelin?

A

Endothelial, mesangial, and tubular cells

43
Q

What are the stimuli for endothelin secretion?

A

Shear stress, angiotensin II, catecholamines

44
Q

How does endothelin affect RBF and GFR?

A

Constriction of afferent and efferent arterioles decreases GFR and RBF

45
Q

What renal cells release nitric oxide? What are the stimuli? How does it affect RBF and GFR?

A

Synthesized in endothelial cells in response to ACh, histamine, bradykinin, and shear force; increased RBF and GFR

46
Q

What is the major stimulus for renal prostaglandin secretion? What is the effect on RBF and GFR? What can they be inhibited by?

A

Released during severe volume depletion- vasodilates AA and EA, increasing RBF and GFR; inhibited by NSAIDs

47
Q

How can surgery and NSAIDs cause acute kidney injury?

A

There will be unopposed renal vasoconstriction which will decrease RBF, leading to ischemia, cell death and decreased GFR (0) and decrease Na+ excretion

48
Q

What are the effects of Dopamine on renal parameters? Through what receptor are the effects mediated?

A

Increases GFR, RBF, UnaV, and UV; D1 receptor

49
Q

What can be used to treat oliguric acute renal failure

A

Dopamine

Physiology Block 4- Renal Physiology (9 decks)

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