I have a question regarding the reason behind the 2 bipolar cells.

So, from my understanding we have both on and off bipolar cells and from the numerous diagrams I have seen, I find that most show a single cone attached to both an off and a on bipolar cell.

The on bipolar cell reacts in an inhibitory manner to glutamate and so if light hits a photoreceptor attached to this bipolar cell, less glutamate is released and so the bipolar cell will become depolarised.

The off bipolar cell is the opposite as it finds glutamate to be excitatory and so it will become depolarised in the dark.

My question is, in the light if a single cone has light presented to it, it will become hyper polarised and so will release less glutamate. If the bipolar cells attached to this cone have opposite effects as in one will become depolarised and one will become hyper polarised what is the reason for the off bipolar cell, why would we need that cell if it only becomes depolarised and doesn't result in anything?

A second question is, do the bipolar cells connect to corresponding ganglion cells for example, on bipolar cell connects only to on-centre ganglion cell? If so why is this?

Lastly, we also have single cones that connect to single bipolar cells. Are these cells on or off bipolar cells I assume they are on because if they were off we wouldn't be able to sense anything as the cell would be hyper polarised and so wouldn't cause the ganglion cell to reach an action potential. Is this thinking correct?


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