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How Receptors of the Eye Conduct Information via the Optic Nerve

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  • 1:04 Photoreceptors
  • 1:42 Photopsin
  • 2:27 Rhodopsin
  • 3:54 Optic Nerve
  • 5:05 Lesson Summary
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Lesson Transcript
Instructor: Artem Cheprasov
You will learn how your eyes are able to see the image in front of you thanks to special cells called photoreceptors. In addition, these receptors have very important proteins called rhodopsin and photopsin; and all of these things work together to transmit information to your optic nerve.

Our Amazing Eyes

The rods and cones in the retina convert light into electrical signals
Eye Retina Diagram

Your eyes are a very complex combination of big, small, and ultra-small structures. It seems that with every passing year, the more scientists look into our own eyes, the more complex this amazing structure becomes.

There are very large, relatively speaking, structures that help us see, like the lens, which helps to bend and focus light entering our eye. Then there is a thin layer all the way at the back of our eye called the retina, which has cells called rods and cones, which transmit information provided by light via electrical signals up to our brain. Our cones help us see in color during the day, while the rod cells helps us see at night.

What's really amazing is that while these cells are really small, there are even smaller structures that are part of the cells that help us see. Without them, the rods and cones would be unable to do their job!

Photoreceptors

The rods and cones located in the retina are highly specialized neurons that convert information provided by light into electrical signals that are conducted to our brain; we call these cells by a general term known as photoreceptors. They are essentially little nerves with specialized endings called receptors, which catch light particles called photons and convert the information these photons provide into electrical signals that our brain can interpret and process into a visual image we can understand.

Photopsin

You'd think that microscopic photoreceptors, called rods and cones, are as small as we can get in the eye, but you'd be wrong! There are even smaller parts of our eye that allow for our rods and cones to function.

One of these tiny little things is a light-sensitive protein responsible for color vision located in the cone cells of the eye's retina, which we call photopsin. If you recall, our cone cells are responsible for vision during the day and for our color vision. Therefore, it should make sense that photopsins, located in cone cells, are sensitive to light and help in our ability to see color.

Photopsin and rhodopsin are found in the cones and rods, respectively
Photopsin Rhodopsin

Rhodopsin

Not to be outdone, the rod cells located in your retina have a similar protein. If you recall, rod cells are responsible for night vision. They have a light-sensitive protein responsible for vision in low light conditions called a rhodopsin. The interesting thing about rhodopsin is how it functions. There's a little experiment you can do yourself to prove that what I'm about to say isn't a lie.

Stay in a very well lit room for about a minute and just look around as you hum and haw. After a minute passes by step into a very dark room, like a bathroom, or just turn off all the lights if it's dark outside. You'll notice that if you try to walk around right away, you're likely to bump into things. If, however, you were to stand there and allow your eyes to adjust to the low light for several minutes, you'll be able to see much better than you did immediately after you turned off all of the lights.

This is all because rhodopsin proteins are inactivated by light, and the photopsins in your cone cells need light to see. Therefore, once the lights are turned off, your cone cells are useless, and it will take several minutes for the rhodopsin in rod cells to fully regenerate and give you the ability to see in the dark with maximal effectiveness.

Optic Nerve

It's important to realize where rhodopsins and photopsins fit in our ability to see. Essentially, what happens is that light particles called photons hit photopsin and rhodopsin proteins. You can think of these proteins as light sensors. If a particle of light hits either one of these sensors, they change the shape of their protein structure.

Cranial nerve II sends information from the retina to the brain
Optic Nerve Diagram

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