Renal Function Flashcards
List the 3 things that compose the Glomerular Filtration Barrier
1) Capillary Endothelium
2) Glomerular Basement Membrane
3) Podocyte Epithelium
Molecules < ___ A are freely filtered
20
Molecules > ___ A are not filtered
42
Lammina Rara Externa is exposed to the ____
Bowmans Capsule
Lamina Rara Interna Is exposed to ___
Blood
Describe what the Lamina Rara Interna and Lamina Rara Externa are composed of and how it contributes to the charge of the GBM.
1) Proteoglycans, Predominately Heparin Sulfate
2) Have electronegative charge
How does the Glycocalyx contribute to the charge of the GBM?
Provides a negative charge
Concentrations are ___ on both sides of the GBM
Equal
How do you calculate Urinary Excretion
Amount Filtered - Amount reabsorbed + Amount Secreted
How do you calculate Tubular Reabsorption?
Glomerular Filtration - Urinary Excretion + Amount Secreted
If excretion > filtration, then ____ must have occurred
Tubular secretion
In terms of the Kidney, Arterial input must equal ____ + ____
1) Venous Output
2) Urine Output
How do you calculate urinary concentration of X (Ux)?
Ux = Concentration/Volume
Define Urinary Concentration
Concentration of that substance in the urine in a given volume
How do you calcular Urine Flow Rate?
V = Urine volume/ time
How do you calculate urine excretion rate?
Ux * V
Urinary Concentration multiplied by the Urine Flow Rate
Urine excretion rate is directly porp. to ___ and __
Urine Concentration and Urine Flow Rate
Clearance is a ____ rate
Flow
Define Renal Clearance
Volume of plasma completely cleared of a substance by the kidneys per unit time
Renal Clearance is the ratio of:::
urinary Excretion (Ux * V) to Plasma Concentration (Px)
What are the units for Renal Clearance and what does it mean?
1) Volume per unit time
2) Volume of plasma cleared of the substance per unit time
What is the Equation of Renal Clearance of a Substance
Cx = Ux * V/ Px
Define Glomular Filtrate (GF)
The fluid filtered across the glomerular capillaries into Bowns Space
____ = Volume of plasma filtered into the combined nephrons of both kidneys per unit of time (mL/min)
Glomerular Filtration Rate (GFR)
How do you calculate Capillary filtration coefficient (Kf)
Permeability * Surface Area
What is the normal Filtration Frcation?
20%
How do you calculate Filtration Fraction?
FF = GFR/RBF
What does the Filtration Fraction represent?
Fraction of RBF that is filtered across the Glomerulus and reaches the tubules
How will an increased of ultrafiltration pressue influence FF?
Increase
FF = GFR/RBF; so as Ultrafiltration pressure increases GFR will increase leading to an increase in FF.
How does an increase of RBF influence FF?
Decreases
Conceptually why does efferent arteriole oncotic pressure increase wjem FF increases?
Increased fluid will be filtered leaving increased protein in the arterioles. This leads to an increase of oncotic pressure in the efferent arteriole.
With a decreased filtration fraction the oncotic pressure in the efferent arteriole will ____
Decrease
How is Filtered Load different from Filtration Fraction. How do you calculate both?
1) Filtered Load is about a specific substance, at which it is getting filtered. To calculate Filtered Load, Multiply GFR with Plasma Conc. of that substance
2) Filtration Fraction is the ratio of GFR to RBF. The Equation is FF= GFR/RBF
You can use ___ to estimate GFR
Renal Clearance
What is normal GFR
125 mL/min
GFR is directly proportional to renal clearance if:
1) Substance must be freely filterable in the glomeruli
2) Substance must be neither reabsorberd nor secreted by the renal tubules
3) Substances must not be synthesized, broker down, or accumulated by the kidney
4) Substances must be physiological inert (not toxic and without effect on renal function)
What is the equation for renal clearance
Cx = Ux * V/ Px
You can calculate GFR by measuring Clearance for which twoo molecules?
Creatinine
Inulin
Systemic Sympathetic Stimulation actives Local renal sympatheic nerves. What does this activation lead to?
1) Constriction of renal arterioldes (decreases GFR)
2) Increases Tubular Reabsorption of Water and Salt
3) Activates RAAS (further increases tubular reabsorption)
There are greater number of alpha 1 receptors on ____ vs ___ arterioles. This leads to a powerful constriction upon sympathetic stimulation.
1) Afferent
2) Efferent
Other than RAAS how does sympathtics increase tubular reabsorption of water and salt?
Na-K ATPase via alpha 1 receptor
What type of receptor simulates Renin release and activation of RAAS?
B1
What are the three physical factors that contribute to GFR
1) Hydraulic Conductivity (Lp)
2) Surface area for filtration (Sf)
3) Capillary Ultrafiltration Pressure (Puf)
How do you calculate GFR when taking in consideration of Hydraulic Conductivity, Surface Area for Filtration, and Capillary Ultrafiltration Pressure?
GFR = Kf * Puf
Kf = Ultrafiltration Constant; Product of Surface area * Hydraulic Conductivity
Define Hydraulic conductivity
Permeability/porosity of the fenestrated endothelium
How do you calculate Puf?
Ultrafiltration Pressure = Pgc - Pbc - piegc
How does an increase in ultrafiltration coefficient affect the GFR?
Increases GFR
How does an increase in Ultrafiltrate Pressure effect GFR?
Increases
Ultrafiltrate coefficient and Ultrafiltrate Pressure are (Inversely/directly) Porp. to GFR?
Directly
What is the main variable that can change Puf.
Pgc
Describe what determines Pgc. (3x)
1) Renal arterial blood pressure
2) Afferent arteriolar resistance
3) Efferent arteriolar resistance
What influences Kf (Ultrafiltration Coefficient)
1) Surface Area
2) Permeability
What role do glomerular mesangial cells play in influencing Sf?
1) Decrease Sf when contract
2) Increase Sf when relaxed
How does Constriction and Dilation of Afferent Arteriole affect: Puf, GFR, RBF, and Pgc
1) Constriction:
- Puf: Decreases
- GFR: Decrease
- RBF: Decrease
- Pgc: Decreases
2) Dilation
- Puf: Increase
- GFR: Increase
- RBF: Increase
- Pgc: Increase
How does Constriction and Dilation of Efferent Arteriole affect: Puf, GFR, RBF, and Pgc
1) Constriction
- Puf: Increase
- GFR: Increase
- RBF: Decrease
- Pgc: Increase
2) Dilation
- Puf: Decrease
- RBF: Increase
- GFR: Decrease
- Pgc: Decrease
List molecules that cause renal vasoconstriction. ?(4x)
1) Sympathetics (Catecholamines)
2) Endothelin
3) ATP/adenosine
4) Angiotensin II
List molecules that cause renal vasodilation (6x)
1) Prostagladins
2) Bradykinin
3) Nitric oxide
4) Dopamine
5) Atrial Natriuretic Peptide
6) ACE-Inhibitor
What molecule primarily constrics efferent arterioles? What does this lead to interms of GFR and RBF?
Angiotensin II
Increased GFR
Decreased RBF
Sympathetics and Catecholamines affect which more: Efferents or Afferents? Why?
Afferents due to increased alpha 1 receptors
What does Increasing GFR do to PTC?
1) Increases PTC oncotic Pressure
2) More stuff dumped into PT
*** Both of these result in increased reabsorption rates in the tubules!!!
Periods of High Blood Pressure in the kidneys leads to local myogenic feedback reflex. Describe this reflex.
1) Results in Afferent Arteriolar Constriction
2) Results in Efferent Arteriolar Dialtion
Describe Function of Tubuloglomerular Feedback
Maintains constanat Na+ delivery to the distal tubule and constant GFR
In tubuloglomerular feed back, macula densa cells are communicating with ____ cells
JG
What is apart of the Juxtaglomerular Apparatus
1) Macula Densa Cells
2) Juxtaglomerular (Granular) Cells
- Renin
3) Extraglomerular Mesangial (Iacis) Cells
Describe what occurs when their is increased NaCl delivery to macula densa.
1) Increased Na+ reabsorbed via NKCC2
2) More ATP/adenosine is released
3) Calcium is released to vascular smooth muscle cells surrounding afferent arteriole
4) Afferent arteriole constricts
5) Decreased GFR and Decreased Renin release
Describe what occrs when the macula densa senses that there is decreased NaCl
1) Decreased reabsorbed via NKCC2
2) :Less ATP/adenosine is released
3) Calcium not released in vascular smooth muscle cells
4) Afferent Arteriole Relaxes
5) Increases GFR
6) Increased Renin released
What promotes Renin Secretion?
1) Decreased NaCl delivery to Macula Densa
2) Renal Sympathetic Stimulation via B1 receptor activation in JG apparatus
How can macula densa dialate afferent arteriole
Via NO
List the actions of Angiotensin II
1) Promotes Aldosterone Secretion
2) Vasoconstrict Efferents Arteriole
3) Enhances TGF
4) Stimulates thirst and ADH release
Integrated Response to decreased ECV: Sympathetics
1) increases renal vascular resistance
2) Increased Na+ reabsorption
3) Enhances renin release (indirectly)
What is the major factor in controlling ADH response?
Osmolarity
The main purpose of Autoregulation and Tubuloglomerular feed back is to _______
Protext the glomerulus and stabilize GFR
The main purpose for extrinsic renal hemodynamics: Sympathetic nerves, hormones, and composition of blood is to __________
Correct body fluid disturbances and stabilize blood pressure
What is the equation for Fractional Excretion. What is the equation when using it for creatinine?
FEx = Amount of X excreted/ Amount of X Filtered
= Ux * V/ Px * GFR
= Uc * Pcr/ Px * Ucr
Describe Fractional Excretion
Percentage of whatever has beem filtered actually gets excreted
