Flashcards in Renal: Dynamics of Glomerular Filtration Deck (36):
What does Glomerular filtrate consists of?
It's very much like blood plasma, however, it contains very little total protein. Consists mainly of inorganic ions and low-molecular-weight organic solutes in virtually the same concentrations as in the plasma.
What does "Freely Filtered" mean?
Substances that are present in the filtrate at the same concentration as in the plasma
What components of blood are freely filtered?
Ions (Na, K, CL, HCO3)
Neutral organics (glucose and Urea)
Peptides (insulin and ADH)
Volume of filtrate formed per unit time = Glomerular Filtration Rate. What is the normal GFR?
What is the net filtration of fluid across all other capillaries (besides the Glomerulus) in the body ?
What is the average total volume of plasma in humans?
3L. ENTIRE plasma is filtered by the kidneys some 60 times a day.
Where is the site of Plasma Filtration?
What determines barriers of Glomerular Filtration?
Glomerulus Cell Types:
What are the Glomerulus Cell Types' functions?
Podocytes: help keep things out based on size
Fenestrated Epithelium: Filter things based on size
Mesangial: modified smooth muscle cells, lay down extra-cellular matrix proteins; Keep things out based on charge
SUM of the Hydrostatic Pressures and the osmotic pressures resulting from protein SUBTRACTED by the oncotic or colloid osmotic pressures
Net Filtration Pressure (NFP)
HPglo - ( ONCOTICglo + HPbowmanspace)
Hydrostatic pressure: Glomerulus and Bowman Space
Oncotic pressure of fluid: Glomerulus and Bowman Space
What is the Filtration Rate Equation?
Rate of Filtration= Kf x NFP
Kf *(HydrostaticPressureGC - HydrostaticPressureBC - OncoticPressureGC)
= Kf * NFP
Pressure that pushes fluid out blood into capsule; FAVOR filtration
Pressure that pushes fluid into blood; OPPOSE filtration
What is the net outward pressure if the Afferent arteriole has 45mmHg (HPglo), -10mmHg (HPbowspace), -25mmHg (ONCOTICglo)?
If Blood Pressure drops 10mmHg of HPglo, the net outward pressure/filtration pressure equals what then?
What portion of the NFP equation favors filtration?
What portion of the NFP equation opposes filtration?
ONCOTICglo , HPbowspace
What is the relationship between Kf and GFR?
Decrease Kf, Decrease GFR
What can change Kf?
Glomerular disease and drugs.
Mesangial contraction, reducing area available for filtration.
Hydrostatic Pressure of the Glomerulus comes from what?
True/False: Hydrostatic Pressure of the Bowman Space is very constant
If you Dilate Afferents, is GFR increased or decreased?
If you Dilate Afferents and Constrict Efferents, is GFR increased or decreased?
What is the relationship between Hydrostatic Pressure of Bowman Space and GFR?
Decreased GFR, Increased Hydrostatic Pressure of Bowman Space
What is the relationship between Oncotic Pressure of Glomerulus and GFR?
Decreased Oncotic Pressure of Glomerulus, Increase GFR
Amount of substance that is filtered per unit time and enters the nephron
Filtered Load Equation? (only works for freely filtered substances)
125 ml/min * 140 mEq/L = 17.5 mEq/min.
What are the short and long-term affects from Autoregulation?
Myogenic response (short-term)
Tubuloglomerular Feedback (long-term)
Concentraion of glucose in plasma is 100 mg/dL and the GFR is 125 ml/min. How much glucose is filtered per min?
A drug is noted to cause a decrease in GFR. Identify 4 possible actions of the drug that might decrease GFR.
1 Constrict glomerular mesangial cells, and decrease Kf.
2 Lower arterial pressure and hence HPglo
3 Constrict the afferent arteriole, and hence reduce HPglo
4. Dilated the efferent arteriole and reduce HPglo
A drug is noted to cause an increase in GFR with no change in net filtration pressure. What might the drug by doing?
It might be increasing Kf
If you Constrict Afferents, is GFR increased or decreased?