ABSTRACT
Photoreceptors synapse with bipolar cells. Two types of bipolar cell can be distinguished on the basis of both morphology and physiological responses. Those with processes that form triad ribbon synapses (Figure 1) deep in the photoreceptor terminal are invaginating bipolar cells and they depolarize in response to light striking the photoreceptor. Triad ribbon synapses are so called because they have three postsynaptic components, the bipolar cell dendrite and dendrites of two horizontal cells. By contrast, flat bipolar cells form superficial basal synapses with photoreceptors and hyperpolarize in response to light.
