Retina bipolar cell
The bipolar cells of the retina are nerve cells of the retina with a bipolar structure. You will also shortly called bipolar cells, because outside of the retina occur bipolar neurons relatively rare.
Your task is to collect the information of the light-sensitive photoreceptors ( rods and cones ) to prioritize and forward them to the ganglion cells of the retina. The extensions of the one bipolar form synapses in the outer plexiform layer (OPL ) and the other in the inner plexiform layer ( IPL) of the retina. The cell bodies of bipolar cells in between in the inner nuclear layer (INL ). In the retina of mammals can be found next to a type of rod -driven, depending on the species from eight to eleven types of cone bipolar cells controlled.
Excitation forwarding
Similar to the photoreceptors, of which the bipolar cells receive signals, they have a special feature of the excitation line: In contrast to most other neurons encode information by graduated changes in potential, which then cause changes in the amount of undistributed messengers ( neurotransmitters) lead (see also the more detailed description of this excitation forwarding for rods).
Contrary to the previous belief that bipolar cells encode information exclusively to these analogous manner, more recent results suggest that some particular types of bipolar cells in mice and fish also also make clear all-or -nothing signals by which the flow of information to the retinal ganglion cells is divided into time blocks.
Species
There are two types of bipolar cells according to the nature of their arousal response: on- cells and off- cells. This name describes their behavior when exposed to light on the upstream receptor cells. The distributed of these ( presynaptic ) neurotransmitter glutamate in both cases is the same, but has he ( postsynaptic ) an opposite effect on on- and off- bipolar cells.
Ganglion cells
The axons of the ganglion cells form the optic nerve as the nerve fiber layer, the innermost layer of the retina, and after leaving the eye. Each of these cells is assigned a specific area of the retina as their receptive field of the relations of bipolar cells. On- center cells are particularly active when light falls on the center of the receptive field and reduce their activity when the surrounding the periphery of the receptive field center is exposed. Off-center cells respond exactly the opposite: light falls onto the center, they are less active; Light falls on the periphery, they are more active.
Lateral interconnections
The bipolar cells derive remanufactured signals of the photoreceptors to the ganglion cells, but there are a variety of lateral ( side ) links with other nerve cells of the retina, which significantly affect this activity forwarding. At the level of the synapses between the photoreceptors and the bipolar cells, these lateral connections and influences are formed by the horizontal cells. At the level of the synapses between bipolar and ganglion cells, amacrine cells form these interconnections.