The original assassin returns with the digital release of StriderÂ® for the Xbox OneÂ®, Xbox 360Â®, PlayStationÂ®4, PlayStationÂ®3 and PC.
To address your question, here's a basic picture of the glomerulus, from Gray's Anatomy. The afferent arteriole is in red, and the efferent arteriole in blue. The glomerular filtration rate (GFR) depends on the pressure difference between the two, which affects the hydrostatic pressure at the glomerulus. Constriction of the afferent arteriole decreases the blood flow into the glomerulus and thus the glomerular hydrostatic pressure, which leads to a decrease in GFR.
Initially moderate constriction of the efferent arteriole leads to an increase if capillary hydrostatic pressure and thus an increase in GFR, and a decrease in renal blood flow.