Retinal Photoreceptors

The retinal photoreceptors and retinal ganglion are only a couple of synapse distant apart but the responses from the ganglion cells are more diverse than the ones observed from the photoreceptor (1). The bipolar cells serve as a direct pathway linking the ganglion cells and the photoreceptors. Bipolar cells are retinal interneurons that have two protrusions, one that goes up and one that goes down. This structure layout is an indicator of the cells function, they link the inner and outer retina. The bipolar cells contact photoreceptors and transmit the signals to the inner plexiform layer of the retina. The inner plexiform layer is where the axon terminals of different bipolar cells arrange into one specific inner plexiform layer and give synaptic signals to amacrine and retinal ganglion cells. Retinal ganglion cells are neurons that conduct output signals while the amacrine cells presynaptic side inhibit the terminals of bipolar ells and the postsynaptic side inhibits the dendrites of …show more content…
OFF center cells are hyperpolarized by the same stimuli. Both cell types repolarize by light stimulation of the peripheral receptive field outside the center. Some bipolar cells postsynapticaly are only cones, some are only rods while other can receive input from both rods and cones. Different bipolar cell types express different glutamate receptors. The axon terminals of bipolar cells can be either monostratified or mulistratified. The cells are also differentiated into midget or diffuse type based on the extent of the dendrite tree. Midget bipolar cells interact with once cone while diffuse cells interact with many cones. The location of the dendrite tips also differentiate the bipolar cells. Flat tips are located on the surface of photoreceptor synaptic terminals. Invaginating cells penetrate the photoreceptor synaptic terminal and approach the presynaptic ribbons