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Renal Exam 1 > Lecture 5 > Flashcards

Lecture 5 Flashcards

1
Q

4 Starling forces that affect filtration

A

1. PGC- Hydrostatic pressure in the GC. Favors filtration

2. PBC- hydrostatic pressure in the BC. Does not favor filtration

3. π<strong>GC</strong>- GC oncotic pressure. Does not favor filtration

4. π<strong>BC</strong>- BC oncotic pressure- Favors filtration

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2
Q

What are the normal values of the 4 starling forces?

A

1. PGC- 60mmHg

2. PBC- 18mmHg

3. πGC-32mmHg

4. πBC- 0mmHg

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3
Q

Based on the normal values of the Starling forces, what would the [Net Filtration Pressure]?

A

NFP (also called the capillary ultrafiltration pressure) = (PGC+ πBC)- (PBC+ πGC)

= (60+0) - (18+ 32)

=10 mmHg

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4
Q

What are the three factors that contribute to GFR?

A
  1. Hydraulic conductivity (Lp)- the permeability of the fenestrated endothelium (Lp)
  2. Surface area (Sf) of the filtration membrane

—-Kf (ultrafiltration coefficient)= Hydraulic conductivity (Lp) * surface area (Sf)—-

  1. Capillary ultrafiltration pressure (PUF)
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5
Q

—Equation—

GFR

A

_GFR= Kf * PUF_

Kf= Lp * Sf

PUF= PGC- PBC-πBC

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6
Q

How can we alter PUF?

A

PUF can be altered by

Changing PGC*, PBC and πGC

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7
Q

What determines PGC?

A

1. BP in the renal artery

2. Afferent arteriole resistance

3. Effecrent arteriole resistance

-the last two are altered by changing the radius of the artery-

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8
Q

GFR= Kf * PUF

What exactly is Kf (ultrafiltration coefficient)?

A

Kf = the hydralaulic conductivity * SA

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9
Q

Glomerular mesangial cells alter Kf.

How?

A

Glomerular mesangial cells alters the SA of the glomerular capillaries.

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10
Q

How does the hydrostatic pressure in the renal vasculature change as you go from the renal artery–> renal vein?

A

Hydrostatic pressure decreases.

Sharp declines exist at the afferent and efferent arterioles because they are sites of regulation via constriction and dilation.

-Across the glomerular capillaries, a relatively high hydrostatic pressure is maintained.

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11
Q

PUF changes along the glomerular capillary from the afferent–> efferent arteriole. How?

A
  1. Filtration is favored at the begining of the afferent arterioles (PGC>πGC); causing it to go from GC–> BC
  2. Pressure within BC drive it through tubule
  3. PGC decreases as you go along and πGC increases.

When the forces balance, there is no filtration. The area of the GC where filtration does not occur is reserved; meaning that if we need more, we can alter the forces that DO NOT favor filtration.

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12
Q

GFR changes according to the needs of the body. πGC increases when we do not want to filtrate, creating what?

A

A wasted capillary that is in reserve.

If we need to use it, we can alter GFR.

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13
Q

As we go along the capillary, PUF (and hence, filtration), is greater when blood flow is lower/higher and when more of the GC is exposed to a net ________, which increases the _______ for filtration.

A

As we go along the capillary, PUF (and hence, filtration), is greater when blood flow is higher and when more of the GC is exposed to a net driving force, which increases the SA for filtration.

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14
Q

Constriction of the afferent arteriole

____ PGC

____ GFR

_____ RBF

A

Decrease PGC

Decrease GFR

Decrease RBF

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15
Q

Dilation of the afferent arteriole

____ PGC

____ GFR

_____ RBF

A

Increase PGC

Increase GFR

Increase RBF

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16
Q

Constriction of the efferent arteriole

____ PGC

____ GFR

_____ RBF

A

Causes pressure to back up.

Increase PGC

Increase PGC

Decrease RBF

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17
Q

Dilation of the efferent arteriole

____ PGC

____ GFR

_____ RBF

A

Decrease PGC

Decrease GFR

Increase RBF

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18
Q

What are the recipricol changes in affterent and efferent arteriolar resistance?

A

Afferent and efferent work together to maintain GFR

  • When afferent pressure inc, efferent pressure decreases
  • dec RPF causes dec GFR

when afferent pressure dec, efferent pressure increases

  • initially, high Pgc causes high GFR despite lower RPF
  • eventually, low RPF dominates and GFR falls
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19
Q

There is a _____ decrease in hydrostatic pressure in the GC!

A

SMALL

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20
Q

What happens to hydrostatic pressure when during afferent arteriolar constriction?

Efferent arteriolar constriction?

A

Afferent arteriolar constriction–> big drop in hydrostatic pressure at the afferent arteriole and smaller, big big drop at the efferent arteriole .

Efferent arteriolar constriction–> drop in affterent arteriole hydrostatic pressure but bigger in the efferent arteriole.

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21
Q

How does oxygen consumption of the kidney compare to the brain?

A

The kidney consume O2 at 2x the rate of the brain d/t reabsorption, but has 7x the blood flow.

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22
Q

As more Na+ is being reabsorbed= ____ O2 consumption

A

Increases linearly.

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23
Q

What are the physiologic controls of GF and RBF? (3)

A

1. Sympathetics

2. Hormones

3. Vasoactive signals

-they affect PGC and πGC-

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24
Q

Intrinsic and extrinsic factors alter renal hemodynamics.

What are the 2 intrinsic factors and the 3 extrinsic factors?

A

Intrinsic

  1. Autoregulation
  2. Tubuloglomerular feedback

Extrinsic

  1. Sympathetic nerves
  2. Hormones
  3. Composition of the blood.
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25
Q

Sympathetics have vasomotor control. Describe this.

A

Sympathetic NS will cause preferential constriction of afferent arteriole via the A1-Receptor (but also afffects efferent), causing a decrease in RBF and GFR; decreasing urine output.

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26
Q

What are vasoconstrictors that act under sympathetics?

A

1. Sympathetic nerves (catecholamines)

2. Angiotensin 2

3. Endothelin

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27
Q

What are vasodilators that act under sympathetics? (6)

A

1. PGE2

2. PGI2

3. NO

4. Bradykinin

5. Dopamine

6. ANP

28
Q

What is glomerulartubular balance?

A

Glomerulartubular balance increases the rate of reabsorption when GFR rises. How?

Higher GFR =

    1. Changes in pressure in the efferent arteriole and peritubular capillaries: they will have a higher πGC
    1. Flow rate and reabsorptive rate are connected.
      * Greater filtered load of normally filtered substances. Many co-transport Na+ in the proximal tubule. This increase delivery of organic solutes that is released d/t increased GFR and preferential reabsorption of Na would cause an increase in the delivery of Cl- in the late proximal tubule.
      • Anion gradient would facilitate the passive reabsorption of organic solutes and NaCl in this area.
    1. Increased GFR and fluid flow through the proximal tubule increases shear strain on the apical microvillus, which increases the insertion of Na+ transporters on the apical membrane.
29
Q

What are is autoregulation?

A

Autoregulation maintains a RBF and GFR within a narrow limit of BP (80- 170mmHg). This occurs via 2 mechanisms

  1. Local reflex called the myogenic reflex
  2. Physiological feedback called the tubuloglomerular feedback
30
Q

What is the local reflex and physiological reflex?

A

Local myogenic reflex is d/t intrinsic property of SM cells.

Physiological feedback occurs via tubuloglomerular feedback at the juxtaglomerular apparatus.

31
Q

What is the autoregulatory range and what does this mean?

A

80-170 mmHg

At these ranges, autoregulation will maintain a stable GFR, even when BP fluctuates

If BP drops below or above, we have a problem.

32
Q

BP below 80mmHg

A

Decrease in RBF

Decrease in GFR

33
Q

BP above 170mmHg

A

Increase RBF

Increase GFR

34
Q

The local myogenic feedback reflex causes the smooth muscles of the BV to contract. What

A

High BP–> - SM of the vessels contract, causing afferent arteriole to constrict and efferent arteriole to dilate via

1. Ca2+ signaling.

35
Q

Juxtalomedullary apparatus is made up of macula densa, JGC and mesengial cells. How does the JGA regulate tubuloglomerular feedback?

A

JGA is located where the afferent arteriole (juxtaglomerular cells) and distal convoluted tubule (macula dense cells) touch.

    1. Macula densa is a sensory organ that senses amount of NaCl in tube via Na/K/Cl- transporter, causing it to go inside.
      * MC releases ATP/ adenosine , which binds to the receptors on the mesengial cells (feedback)
      * ***This msg is transduced via the mesangial cells****
    1. This increases intracellular Ca2+.
      * An increase in intracellar Ca2+ in SM will signal vasoconstriction of the afferent arteriole
      * An increase in intracellular Ca2+ in the JGC cells will inhibit the release of renin

Result: decrease GFR= decrease Na reabsorption when too much NaCl

36
Q

tubuloglomerular feedback

maintains a constant _____ delivery to _______ and maintain a constant ____.

A

Na+ delivery to the distal tubule and maintains a constant GFR.

37
Q

What happens where there is a increase in renal perfusion pressure?

A

Increase in renal perfusion pressure= Increase in RBF and GFR

–>

Increase in NaCl delivery to JGA (macula densa)

–>

MD releases adenosine

–>

Afferent arteriole vasoconstricts

–> decrease RBF and GFR

38
Q

What happens where there is a decrease in renal perfusion pressure?

A

Decrease in renal PP= Decrease GFR and RBF

–>

Decrease in PGC

–>

Decrease in GFR

–>

Decrease in NaCl delivery to MD and an increase in proximal NaCl reabsorption

–>

MD signals NO release and JG cells to secrete renin and

–>

A. Renin–> angiotensin 2

B. NO is released

–>

A. A2 causes efferent arteriole vasoconstriction

B. NO causes afferent arteriole vasodilation (dec in resistance)

39
Q

Reduced perfusion pressure stimulates/inhibits renin secretion by the afferent arteriole.

A

stimulates

40
Q

Increased perfusion pressure stimulates/inhibits renin secretion by the afferent arteriole.

41
Q

Sympathetic activity increases/decreases renin secretion via ___ receptor

Sympathetic inactivity increases/decreases renin secretion

A

Sympathetic activity–> increases renin secretion via B-R.

Sympathetic inactivity decreases renin secretion.

42
Q

Decrease in NaCl delivery to the macula densa=

______ renin secretion.

43
Q

Increase in NaCl delivery to the macula densa=

______ renin secretion.

44
Q

What factors increase sensitivity to TGF? (5)

A
  1. Volume contraction
  2. Adenosine
  3. PGE2
  4. Thromboxane
  5. Ang II
45
Q

What factors decrease sensitivity to TGF? (6)

A
  1. Volume expansion
  2. ANP
  3. NO
  4. cAMP
  5. PGI-2
  6. High protein diet (?)
46
Q

Glomerular-tubular balance and tubuloglomerular feedback

47
Q

Vasodilation of afferent arteriole

-Via: prostaglandin, bradykinin, NO, DA and ANP

affects

RBF, GFR and peritubular capillary hydrostatic pressure how?

A

Increases all

48
Q

Vasoconstriction of afferent arteriole

-Via: ACE-inhibitors

affects

RBF, GFR and peritubular capillary hydrostatic pressure how?

A

Decreases all

49
Q

Vasodilation of efferent arteriole

-Via: sympathetics

affects

RBF, GFR and peritubular capillary hydrostatic pressure how?

A

RBF- increase

GFR- decrease

Peritubular capillary hydrostatic pressure- Increase

50
Q

Vasoconstriction of efferent arteriole

-Via: Angiotensin 2

affects

RBF, GFR and peritubular capillary hydrostatic pressure how?

A

RBF- decreases

GFR- increases or stays the same

Peritubular capillary hydrostatic pressure- decreases

51
Q

What are the main outputs for fluid?

A
  1. Kidneys
  2. Lungs
  3. feces
  4. sweat
  5. skin
52
Q

Normal intake of fluids is ___________: ______ ingested and ____ from the metabolism.

What is the output?

A

2100 ingested

200 from metabolism

What is the output? 2300

53
Q

During heavy excerize, what is the total output of fluids?

54
Q

A decrease in ECF volume loss will do what to the concentration of proteins in our plasma?

55
Q

Most common indicators for

  1. ECF
  2. TBW
  3. Plasma volume
A

ECF- inulin

TBW- H202/3

Plasma volume- 125I-albumin

56
Q

An increase BP and increase blood flow will do what to hydrostatic capillary pressure and filtration

A

Increase both

57
Q

Arteries mainly do _____, while venules mainly do _____

A

reabsorpbtion

58
Q

Concentration of X in ICF/ECF

A

ICF total mOSm= volume of ICF * plasma osmolarity

59
Q

Colloids are large proteins that do not pass the semi-permeable membrane. Ex. is albumin. So if we inject them in the blood, what will they do?

A

Stay there; increase intravascular volume (plasma) because of the high oncotic pressure

60
Q

Crystalloids

A

Water+ electrolytes

They do not go across the plasma membrane into the ICF. They stay in the ECF and distribute evenly within the ECF (plasma and ISF).

61
Q

If we want to increase plasma volume, what IV do we give?

A

Colloids because they do not cross capillary wall and increase oncotic pressure

62
Q

If a patient has hyperosmotic fluid (increase solutes and decrease water), what kind of solution do they need?

A

Hypotonic

-NaCl (0.4%)

DSW- increase the volume of both ISF and ECF because it converts to CO2 and water

63
Q

If a pt hemorrhages 1 L of blood in 5 minutes, you would restore the body fluid balance by giving 1 L of what?

A

0.9 NaCl IV

—Because pt has isotonic volume contraction (decrease ECF, no change in tonicity or ISF volume)—-

Isotonic NaCl restores both.

64
Q

What would happen if we gave the patient 4.5% NaCl?

A

— make plasma hyperosmotic—

—water would leave the cells, causing shrinkage—-

65
Q

When do we give dextrose?

A

Fluid loss

Dehydration

Hypernatremia

66
Q

When do we give normal saline?

A

Shock

Hyponatrema

Blood transfusions

Resuscitation

Diabetic keto-acidosis

67
Q

When do we give lactated ringers?

A

Dehydration

Burns

Lower GI fluid loss

Acute blodd loss

Hypovalemia due to third spacing.

Renal Exam 1 (10 decks)

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