Why rod cells respond to low-intensity light

- A certain threshold value has to be exceeded before generator potential is created in bipolar cells (to which rod cells are connected) - As a no. of rod cells are connected to a single bipolar cell (=retinal convergence), there is much greater chance that the threshold value will be exceeded than if only a single rod rod cell were connected to each bipolar cell - This is due to summation - In order to create a generator potential, the pigment in the rd cells (rhodopsin) must be broken down - There is enough energy from low-intensity light to cause this breakdown