THORAX ABDOMEN AND PELVIS

Detailed explanation-1: -If you contract the afferent arteriole there will be less of a pressure difference between the afferent and efferent arteriole so there will be reduced filtration pressure. However if you constrict the efferent arteriole you are increasing the pressure difference between the two and filtration pressure increase.

Detailed explanation-2: -A decrease in the diameter of the afferent arteriole has the opposite effect. An increase in the efferent arteriolar diameter (decrease in resistance) causes a decrease in the glomerular capillary hydrostatic pressure and a decrease in GFR. A decrease in the diameter of the efferent arteriole has the opposite effect.

Detailed explanation-3: -The main reason that the hydrostatic pressure stays high in the glomerular capillaries is that they don’t coalesce into a vein but rather into an arteriole. The efferent arterioles are high-pressure vessels with muscular walls just like the afferent arterioles.