Unconventional Origins: The Mystery of the Optic Nerve's Cranial Classification

In summary, the optic nerve originates from the retina and continues up till the commencement of the optic chiasma. It is approximately 4 cm long.
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Prashasti
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We had a class on optic nerve today.
Our teacher said that the optic nerve "originates" from the retina, and continues up till the commencement of the optic chiasma, and is, approximately, 4 cm long.
My question is,
Why is it considered to be a cranial nerve when it does not even originate from any of the several nuclei in the brain?
I know that it is related to the Edinger-Westphal nucleus and the facial nerve, but if it is so, why isn't it said to be originating from there?

What I thought was,

Since it is a sensory nerve, it brings the sensations from the eye ball to the brain for their processing, so it muct be studied before backwards. (Just like we study "tributaries" for veins and "branches" for arteries!)
But if it is right, then that'd mean that we don't have any nuclei for any of the sensory nerves!
(This is not true, right?)
 
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Prashasti said:
Why is it considered to be a cranial nerve when it does not even originate from any of the several nuclei in the brain?

From Wikipedia:
The optic nerve is the second of twelve paired cranial nerves and is technically part of the central nervous system, rather than the peripheral nervous system because it is derived from an out-pouching of the diencephalon (optic stalks) during embryonic development. As a consequence, the fibers of the optic nerve are covered with myelin produced by oligodendrocytes, rather than Schwann cells of the peripheral nervous system, and are encased within the meninges. Peripheral neuropathies like Guillain-Barré syndrome do not affect the optic nerve.

In other words, developmentally the optic nerve comes from progenitor cells that are part of the central nervous system and functionally, it resembles neurons from the CNS more than neurons in the PNS.
 
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Ygggdrasil said:
From Wikipedia:
In other words, developmentally the optic nerve comes from progenitor cells that are part of the central nervous system and functionally, it resembles neurons from the CNS more than neurons in the PNS.

It is worth noting that "Cranial" implies it does not connect through the spinal cord. :-)
 
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Related to Unconventional Origins: The Mystery of the Optic Nerve's Cranial Classification

1. What is the course of the optic nerve?

The course of the optic nerve is the path that the nerve takes from the eye to the brain. It is responsible for transmitting visual information from the eye to the brain for processing.

2. How does the optic nerve function?

The optic nerve functions by carrying electrical impulses from the retina of the eye to the brain. These impulses are then processed by the brain to create visual images.

3. Can the course of the optic nerve be affected by disease or injury?

Yes, the course of the optic nerve can be affected by various diseases and injuries. Some common conditions that can damage the optic nerve include glaucoma, optic neuritis, and optic nerve compression.

4. How does the course of the optic nerve differ between humans and other animals?

The course of the optic nerve varies between species. In humans, the optic nerve exits the eye at the back of the eyeball, while in some animals, such as birds, it exits at the front of the eye. Additionally, some animals have more complex optic nerve pathways, allowing for better depth perception and peripheral vision.

5. What are some current research advancements related to the course of the optic nerve?

There are ongoing studies and advancements in understanding the course of the optic nerve and its role in various eye diseases. Researchers are also exploring potential treatments for optic nerve injuries and diseases, such as stem cell therapy and gene therapy.

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