Renal Circulation Flashcards

1
Q

What is the equation for Renal Plasma Flow

A

RPF= RBF x (1-Hct)

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2
Q

What is the equation for Filtration fraction?

A

FF= Glomerular Filtration Rate/ Renal Plasma Flow

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3
Q

How much of the CO do the kidneys receive?

A

~20-25% of CO

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4
Q

What are the two major factors that generate filtrate?

A
  1. Hydraulic pressure in glomerular capillaries

2. Renal blood flow rate

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5
Q

What other factors contribute to filtrate formation?

A

Hydraulic pressure
Renal blood flow rate
Minor- Blood oncotic pressure
Filtration coefficient (how easily you can move fluid across: characteristics of vessel, SA)

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6
Q

What is the equation for blood flow?

A

Flow (Q)= Pressure Change/Resistance

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7
Q

What factors influence resistance in the vessels?

A
  1. Length of blood vessels
  2. Radii of blood vessels (MAJOR factor)
  3. Blood viscosity
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8
Q

What are the effects of vasoconstriction?

A

Decreased flow
pressure up stream increases
downstream pressure decreases

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9
Q

B/c of the presence of of both pre- and post- glomerular capillary sphincters:

  • Glomerular capillary pressure is much (greater/less) than in most capillaries elsewhere in the body.
  • Peritubular capillary pressure is (higher/lower) than in most capillaries elsewhere in the body
A
  1. greater
  2. lower
    These pressure differences facilitate formation of filtrate in glomeruli and reabsorption of fluid from peritubular capillaries.
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10
Q

What are three factors that promote renal constriction?

A
  1. Sympathetic n (catechoamines)
  2. Angiotensin II
  3. Endothelin
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11
Q

What are 5 factors that promote renal constriction?

A
  1. PGE2
  2. PGI2
  3. NO
  4. Bradykinin
  5. Dopamine
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12
Q

What effect do sympathetic nerve fibers have?

A

They activate alpha 1 receptors on afferent and efferent arterioles –> vasoconstriction

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13
Q

How would SNS activation affect on RBF and GFR?

A

Decrease RBF and GFR

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14
Q

What effect does Angiotensin II have?

A

Potent vasoconstrictor
Affects both AA and EA
Greater effect on the efferent arteriole

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15
Q

How would Angiotensin II affect RBF and GFR?

A

Decrease RBF and Inc. GRF

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16
Q

Levels of ATII release influences the relative effects so…..
At low levels of ATII which vessel is influenced more?
At high levels of ATII?

A

At low levels: both AA and EA constrict, then EA> AA, –> inc. GFR

At high levels, both AA and EA constrict, then EA dec. GFR

17
Q

What effect does Prostaglandins (PGE2 and PGI2) have?

A

Vasodilate both vessels

18
Q

Activation of SNS and ATII also activates renal PG production, explain why. (also how it relates to Advil)

A

PG activation is a safety mechanism- vasodilates vessels deep in the kidney to maintain blood flow

19
Q

What effect does Dopamine have on the kidneys (and other organs) at:

  1. Low doses
  2. High doses
A
  1. At low doses:; dilates renal, cerebral, cardiac and splanchic arterioles
    constricts skeletal and cutaneous arterioles
  2. At high doses: vasoconstricts renal arterioles
20
Q

What is autoregulation?

A

system in place that limits changes in kidney function due to changing systemic BP. (protects glomerulus from systemic pressure)

21
Q

What primarily controls autoregulation?

A

The Afferent arteriole.
Theories: Myogenic: physical stretch is detected, open sm. muscle Ca channels –> vasoconstriction
Tubuloglomerular: macula densa senses

22
Q

Net flow across vessel wall depends on:

A
  1. Hydrostatic Pressure on each side
  2. Oncotic Pressure on each side
  3. Filtration coefficient of the vessel wall.
23
Q

Why are NSAIDS toxic to kidneys?

A

They suppress PG production, can have too much vasoconstriction (PG is protective of kidney blood flow)