<prompt> According to myogenic hypothesis of renal autoregulation, the afferent arterioles contract in response to stretch induced byNO releaseNoradrenaline releaseOpening of Ca2 channelsAdenosine release  <response>: Stretch on smooth muscle afferent arterioles opens Ca channel, which causes contraction of afferent arterioles.the medullary interstitium.REGULATION OF GFRRegulation is done by:Blood pressure: AutoregulationResistance of afferent and efferent anterioles- Autoregulation: Constant maintenance of renal blood flow or, GFR over the span of renal perfusion pressure pressure in renal artery minus pressure in renal vein from 80 to about 170mm Hg- Mechanism of autoregulation:i Myogenic mechanism- contraction or relaxation of anteriolar smooth muscle in response to changes in vascular pressures; mediated by Caii Tubule glomerular feedback TGF mechanism-mediated by macula densa cells described later 