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CPR Test 2 > Session 2 pierce > Flashcards

Session 2 pierce Flashcards

1
Q

what are the three layers of the glomerular filtration barrier, and what is the sizes that allow for things to filter through

A

Capillary endothelium
Glomerular basement membrane
Podocyte epithelium

molecules less than 20 A are freely filtered

molecules greater than 42 are not filtered

anything inbetween may or may not be filtered

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2
Q

what is the glycocalyx and what is its function with filtration, what happens if this is lost

A

glomerular endothelium that forms a sticky biogel in the endothelial lumen that helps with filtration
-made of glycoproteins that alter filtration based on charge (negative)

it enhances filtration of cationic dextrans

decreases filterabillity of anionic dextrans

Nephrotoxic serum nephritis will destroy the glycocalyx leading to increased filtration of anions (proteins)

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3
Q

what is freely filtered and what is not freely filtered

A

Freely filtered:

  • water
  • small solutes, glucose, amino acids, electrolytes
  • concentrations equal on both sides of the membrane

Not freely filtered:

  • Large molecules (proteins)
  • formed elements (cells)
  • Miniscule amounts of protein are filtered
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4
Q

equation for urinary excretion

A

Urinary excretion = amount filtered - amount reabsorbed + amount secreted

Ue = F + S - R

use this equation determine any number of theses

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5
Q

what is the significance of what goes into the kidney must come out, eqation

A

the arterial input into the kidney = the venous output out of the kidney + the urine output

X in artery = X in vein + X in ureter

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6
Q

What is the urine excretion rate of x and what does each variable mean

A

x = Ux times V

Ux = the concentration of that substance in the urine

V = Urine flow rate, the rate at which urine is produced. Dependant on fluid intake and fluid homeostasis. Normally if fluid intake is increased, urine flow will increase

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7
Q

what is renal clearance

A

The rate at which substances are removed or cleared from plasma
-Renal clearance means the rate of removal by the kidneys

Renal clearance (C) is the volume of plasma completely cleared of a substance by the kidneys per unit of time

Renal clearance is the ratio of urinary excretion (Ux times V) to plasma concentration (Px)

units are volume per unit time

clearance is a flow rate removed from the blood

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8
Q

what is the equation for renal clearance

A

Cx = (Ux times V)/Px

clearance of a substance = concentration of X in urine times the urine flow rate divided by the concentration of X in the plasma

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9
Q

what is Glomerular filtrate

A

(GF) volume of plasma filtered into the combined nephrons of both kidneys per unit of time

The fluid filtered across the glomerular capillaries into bowmans space

  • protein free
  • cell free
  • similar to plasma (plasma ultrafiltrate), isosmotic to the plasma
  • 20 % of the RBF or RPF
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10
Q

what is the glomerular filtration rate

A

roughly 20 percent of RBF

  • Balance of starling forces (hydrostatic and oncotic forces
  • Capillary filtration coefficient (Kf): Permeabillity x surface area

-Averages 125 mL/day

FF = GFR/RPF

FF is normally 20 percent

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11
Q

what percentage of the RPF is normally absorbed

A

99 percent

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12
Q

what is the filtration fraction

A

The fraction RPF that is filtered across the glomerulus

  • changes with ultrafiltration pressure
  • influenced by blood pressure

as FF increases the oncotic pressure of the efferent arteriole increases, to facilitate reabsorption of tubular fluid

  • this is because as more solution is being filtered out it leaves more concentrataed stuff behind
  • this will increase the oncotic pressure in the efferent arteriole as we move down the arteriole
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13
Q

how is filtered load and filtration fraction not the same? what is the equation for filtered load

A

Filtered load is a rate in mg/min

filtration fraction is the ratio of the GFR/RBF

Filtered load = GFR times Px

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14
Q

how to determine the percentage of the filtered load of something reabsorbed per day and what are the variables at play

A

Filtered load = GFR times Px

Reabsorption = Filtered load - excretion

Ecretion = V times the Ux

variables:

  • GFR
  • PLasma concentration
  • Urine concentration
  • Urine flow rate
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15
Q

when can we use renal clearance to estimate GFR and what are the conditions

A

Filtered amount = excreted amount

that would mean GFR = Ux times V divided by Px
(equation for clearance but with GFR)

GFR is directly proportional to renal clearance if:

  • substance must be freely filtered into glomeruli
  • must be neither absorbed or secreted by renal tubules
  • not be synthesized or broken down or accumulate in kidney
  • must be physiologically inert (not toxic and without effect on renal function)
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16
Q

Examples of substance that can be used to calculate GFR and meets the clearance conditions

A

Inulin, amount excreted is equal to amount filtered

Creatinine

  • dependant on age and muscle mass
  • however small amount approximately 10 percent of creatinine is secreted)
  • not quite ideal
17
Q

What are the three main ways sympathetics increase Bloodpressure via kidneys, the cells they function on, and their receptors

A

Arterial resistance

  • vasoconstriction
  • alpha 1

JG cells

  • renin release + RAAS
  • B1

Na-K-ATPase

  • increased Na+ reabsorption
  • alpha 1
18
Q

what are the forces causing filtration by the glomerular capillaries

A

Starlings equation

Forces favoring filtration:

  • Pgc
  • nBC

Forces opposing filtration:

  • Pbc
  • ngc

net is positive = filtration
net is negative = no filtration

19
Q

what are the three physical factors that contribute to GFR

A

-Hydraulic conductivity (permeabillity of the fenestrated endothelium) Lp

-Surface area for filtration
(Lp x Sf) = ultrafiltration coefficient Kf

-Capillary ultrafiltration pressure Puf

GFR = Kf x Puf

20
Q

how to calculate the ultrafiltration pressure (Puf) and how does it change

A

Puf = Pgc - Pbc - ngc (starlings equation)

nbc = oncotic pressure in bowmans capsule is normally 0
Pgc = Hydrostatic pressure in gc
Pbc = HYdrostatic pressure in bowmans capsule
ngc = oncotic pressure in glomerular capillary

the Pgc can change based on

  • Renal arterial blood ressure
  • afferent arteriolar resistance
  • efferent arteriolar resistance
21
Q

What determines the Ultrafiltration coefficient (kf)

A

Hydraulic conductivity x Surface area = Kf

damage to kidney can effect the surface area and permeabillity

Glomerular mesangial cells can affect the surface area by contracting to decrease the SA or relaxing to increase SA

22
Q

where are the changes of hydrostatic pressures in the renal vasculature

A

Renal artery = high

Afferent arteriole = steep drop

glomerular capillary = relatively high pressure but is maintained throughout
-helps to filter more fluid

Efferent arteriole: steep drop

23
Q

Pgc, GFR, and RBF when vasoconstriction of the afferent arteriole

A

Pgc: decrease

GFR: decrease

RBF: decrease

24
Q

Pgc, GFR, and RBF when vasoconstriction of the efferent arteriole

A

Pgc: increase

GFR: increase

RBF: decrease

25
Q

Pgc, GFR, and RBF when vasodilate the efferent arteriole

A

Pgc: decrease

GFR: decrease

RBF: increase

26
Q

Pgc, GFR, and RBF when vasodilate the afferent arteriole

A

Pgc: increase

GFR: increase

RBF: increase

27
Q

what are some vasoconstrictors

A

sympathetics (catecholamines)
-more alpha 1 on afferent arteriole than efferent

endothelin

ATP/adenosine

Angiotensin II
-primarily constricts the efferent arteriole which raises GFR

28
Q

what are some vasodilators

A
  • prostaglandins
  • Brdykinin
  • Nitric oxide
  • Dopamine
  • Atral natriuretic peptide
  • Ace inhibitor (tends to lower GFR)
29
Q

Mechanisms of Glomerulartubular balance

A

Increase reabsorption rate within the renal tubules when GFR rises (kidney compensates)

  • Change in pressure in the efferent arteriole leads to an increase in GFR leaving more filtered at glomerulus, higher oncotic presssure in the efferent arteriole and peritubular capillary (PTC) (this promotes Na+ reabsorption)
  • Increased delivery of solutes to proximal tubule leads to an increase reabsorption of Na+ due to the lots of solutes
  • also with increased GFR there is an increase shear due to fluid flow that the apical microvilli will upregulate apical sodium transporters to increase Na absorption
30
Q

what are the two Autoregulation methods of the Kidney via the RBF and the GFR

A

Local reflex: between vascular smooth muscle cells (myogenic reflex)

  • blood vessels resist stretch during periods of high blood pressure
  • calcium signaling
  • Afferent arteriolar constriction and efferent arteriolar dilation

Tubuloglomerular feedback

  • Juxtaglomerular apparatus (macula densa cells, juxtaglomerular cells and extraglomerular mesangial cells
  • senses tubular Na+ concentration
  • signals between the macula densa and JG cells to maintain constant Na delivery to the distal tubule and constant gfr
  • renin release
31
Q

when does the macula densa signal

A

increase delivery of NaCl to macula densa

  • Increase ATP/adenosine
  • vasoconstricts afferent arteriole
  • decrease GFR
32
Q

summary of the Tubuloglomerular feedback

A

Macula densa senses NaCl

  • JG cells secrete renin
  • mesangial cell will transduce the message
33
Q

What is fractional excretion

A

what percentage of whatever has been filtered actually gets excreted

FEx = Amount x excreted/amount of X filtered

FEx = ((Ux)(V))/((Px)(GFR))

FEx = ((Ux)(Pcr))/((Px)(Ucr)) (clearance of creatinine

FEx will be lower than 100 percent if reabsorption occurs

FEx will be higher than 100 percent if secretion occurs

CPR Test 2 (25 decks)

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