We present response functions for a large number of emission lines covering a wide variety of ionization states emitted from a spherical broad-line region (BLR). The line emissivities are calculated using a photoionization code for a cloud distribution where the cloud properties and covering factor are constrained by a pressure law. Emissivity-weighted and responsivity-weighted response functions are compared for different lines emitted from the same spatially extended BLR gas, and we discuss their dependences on the radial ionization parameter and density gradients. Depending on the local physical conditions, we show that some lines can have negative response functions, particularly if the BLR contains a region of optically thin clouds