Arteriolar resistance and GFR

Relationship between arteriolar resistance, glomerular filtration rate (GFR), and renal plasma flow (RPF). (a) If flow is constant, constriction of a vessel results in a rise in pressure proximally (P1) and a fall distally (P2). (b) Constriction of the afferent arteriole reduces Pgc and GFR. (c) Constriction of the efferent arteriole, on the other hand, tends to increase Pgc and, in some cases, GFR (depending in part on the effect on RPF). Since constriction of either arteriole also raises renal vascular resistance, RPF will fall in both (b) and (c). Arteriolar vasodilation has the opposite effects.