Final answer:
A decrease in blood pressure leads to vasodilation of the afferent arterioles, resulting in an increased glomerular blood pressure and glomerular filtration rate (GFR).
Step-by-step explanation:
A decrease in blood pressure detected by the afferent arteriole leads to vasodilation to compensate for the drop. This vasodilation results in an increased volume of blood flowing through the glomerulus and thus an increased glomerular filtration rate (GFR). The autoregulatory mechanisms of the kidney, including the myogenic mechanism and the tubuloglomerular feedback, ensure that the GFR is maintained within a proper range, despite changes in systemic blood pressure. These mechanisms facilitate the dilation of the afferent arterioles when blood pressure drops in order to maintain an adequate GFR, and the arterioles constrict when blood pressure is high to prevent excessive GFR.
As such, when the afferent arteriole detects a decrease in blood pressure and vasodilation occurs, both the glomerular blood pressure and the GFR will respond by increasing.