GFR is determined by –
Correct Answer: All of the above
Description: Ans. is 'd' i.e., All of the above Determinants of GFRIncrease glomerular capillary hydrostatic pressure increases GFR. Glomerular hydrostatic pressure is determined by following variables : i) Arterial pressure, ii) Afferent arteriolar resistance; iii) Efferent arteriolar resistance.Increased arterial pressure tends to raise glomerular hydrostatic pressure and, therefore, to increase GFR. Opposite is true for decreased arterial pressure, i.e.. Hypotension causes decrease in GFR.Increased resistance of afferent arterioles (constriction of afferent arterioles) reduces glomerular hydrostatic pressure and decrease GFR. Conversely, dilation of the afferent arterioles increases both glomerular hydrostatic pressure and GFR.Efferent arteriolar constriction has a biphasic effect on GFR. At moderate levels of constriction, there is a slight increase in GFR, but with severe constriction, there is a decrease in GFR. Dilatation of efferent arterile decreases glomerular hydrostatic pressure and therefore decreases GFR.Increased glomerular capillary colloid osmotic (oncotic) pressure decreases GFR. Decreased glomerular capillary colloid osmotic pressure increases GFR, .e.g, in hypoproteinemia. Increased renal blood flow increases GFR by decreasing glomerular capillary' oncotic pressure. Increased RBF causes decrease in filtration fraction (filtration fraction = GFR'RPF). This results in more fluid remaining in the glomerular capillary and dilution of plasma proteins and as a result decrease in oncotic pressure. Conversely, by opposite effect. Decreased renal blood flow decreases GFR.Increased Bowman's capsule hydrostatic pressure (due to increased tubular hydrostatic pressure as a result of obstruction) decreases GFR.Decrease in glomerular capillary filtration coefficient (Kf) decreases GFR. Kf depends on the permeability of the glomerular membrane as well as its surface area. Increased thickness of membrane decreases the permeability and Kf Chronic hypertension and diabetes increases the thickness of glomerular membrane and decrease Kr and thereby GFR.Kf can be altered by the mesangial cells which contract and cause decrease in Kf by decreasing surface area of membrane. Relaxation of mesangial cells increase KjContraction of mesangial cells (therefore decrease in GFR) is produced by : - Endothelin, angiotensin II, vasopressin, norepinephrine, PAF, PDGF, thromboxane A., PGF2 Leukotrienes C4 & D4, Histamine.Relaxation of mesangial cells (therefore increase in GFR) is produced by : - ANP, Dopamine, PGE2,cAMP .
Category:
Physiology
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