<prompt> GFR increases if:Afferent arteriole constrictsAfferent arteriole dilatesEfferent arteriole dilatesnone of the above  <response>: Ans. B. Afferent arteriole dilates,Determinants of the GFR:a. GFR Kf x Net filtration pressureb. Net filtration pressure PG-PB-pGpBi. PG Glomerular hydrostatic pressure 60 mm Hg, promotes filtrationii. PB Hydrostatic pressure in Bowmans capsule 18 mm Hg which opposes filtrationiii. PG Glomerular capillary colloid osmotic pressure 32 mm Hg, which opposes filtrationiv. PB Bowmans capsule colloid osmotic pressure which promotes filtration, normally its value is zerov. ThereforeNet filtration pressure PG-PB-pGpB60-18-32010mmHgc. Kf Glomerular capillary filtration ultrafiltration co-efficient Kf is a measure of the product of the hydraulic conductivity i.e. its permeability and surface area of the glomerular capillaries. Its normal value for kidney is 12.5 mlminmm Hg of filtration pressure or 4.2 mlminmm Hg per 100 gm of kidney.Factors that increase or Decrease GFRa. Kf - although increased Kfraises GFR, and decreased Kfreduces GFR, changes in Kfprobably do not provide a primary mechanism for the normal day to day regulation of GFR Kf - if decreases GFRi. Measangial cells contraction Kf GFR; Angiotensin II important regulator of the mesangial cells contraction contraction area available for filtration.ii. Thickness of the Glomerulary capillary BM i.e. glom. capi. Permeability Kf GFR e.gchr. HTN, DM Agents causing contraction or Relaxation of mesangial cells i.e. or Kf i.e. -or GFR. 