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AQA Biology Direction of Light??
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Attachment 636356Why is the light pointing that way? Surely it's meant to go through the light sensitive cells first ??
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#3
It is shown that way round because - bizarrely - the anatomy of the retina is actually back-to-front in its structure. It's one of those quirks that shows us how the eye evolved - not "logically", but because this was the only way it could be done in the circumstances.
This means that to reach the light-sensitive pigment, light entering the eye has first to pass through the (transparent) layers of nerve cells etc.
After the light hits the pigment layer, the nerve impulse then travels "backwards" to get to the optic nerve and then out to the brain.
Does that make sense? Its described on the wikipaedia page on the retina if you need more detail
This means that to reach the light-sensitive pigment, light entering the eye has first to pass through the (transparent) layers of nerve cells etc.
After the light hits the pigment layer, the nerve impulse then travels "backwards" to get to the optic nerve and then out to the brain.
Does that make sense? Its described on the wikipaedia page on the retina if you need more detail
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(Original post by OxFossil)
It is shown that way round because - bizarrely - the anatomy of the retina is actually back-to-front in its structure. It's one of those quirks that shows us how the eye evolved - not "logically", but because this was the only way it could be done in the circumstances.
This means that to reach the light-sensitive pigment, light entering the eye has first to pass through the (transparent) layers of nerve cells etc.
After the light hits the pigment layer, the nerve impulse then travels "backwards" to get to the optic nerve and then out to the brain.
Does that make sense? Its described on the wikipaedia page on the retina if you need more detail
It is shown that way round because - bizarrely - the anatomy of the retina is actually back-to-front in its structure. It's one of those quirks that shows us how the eye evolved - not "logically", but because this was the only way it could be done in the circumstances.
This means that to reach the light-sensitive pigment, light entering the eye has first to pass through the (transparent) layers of nerve cells etc.
After the light hits the pigment layer, the nerve impulse then travels "backwards" to get to the optic nerve and then out to the brain.
Does that make sense? Its described on the wikipaedia page on the retina if you need more detail
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#5
(Original post by Uni12345678)
I don't understand... surely the optic nerve is right at the back...
I don't understand... surely the optic nerve is right at the back...
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#6
Does this picture help?![Name: F16-01 Human eye.jpg
Views: 232
Size: 71.3 KB]()
See how the "nerve fiber layer" lies on the inside of the eye?
See how the "nerve fiber layer" lies on the inside of the eye?
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(Original post by OxFossil)
Does this picture help?![Name: F16-01 Human eye.jpg
Views: 232
Size: 71.3 KB]()
See how the "nerve fiber layer" lies on the inside of the eye?
Does this picture help?
See how the "nerve fiber layer" lies on the inside of the eye?
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#8
(Original post by Uni12345678)
Okay so I kinda understand, basically the bipolar cells and optic nerve are on top of the rods and cones and light has to go through them to get to the rods and cones. It then travels backwards through those bipolar cells and optic nerve and then dive back in to the eye? So it goes one way, then the other, and then back the same way?
Okay so I kinda understand, basically the bipolar cells and optic nerve are on top of the rods and cones and light has to go through them to get to the rods and cones. It then travels backwards through those bipolar cells and optic nerve and then dive back in to the eye? So it goes one way, then the other, and then back the same way?
The AQA diagram shows it as it really is - which is confusing!
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