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Author Topic:   Neurons and Cranial Nerves (simple question)
JustinC
Member (Idle past 4844 days)
Posts: 624
From: Pittsburgh, PA, USA
Joined: 07-21-2003


Message 1 of 9 (398152)
04-29-2007 12:58 PM


I'm been reading The Idiot's Guide to Understanding the Brain thinking it would be a nice introduction to the subject. Well, just like the other idiots guide I read, it is plagued with problems (not enough diagrams, repeating whole paragraphs, vagueness, etc.).
But I digress. I just have one simple question: are cranial nerves actually bundles of nerves and not just a nerve (singular)? It doesn't say this explicitly but I believe that has to be the case since they are conveying so much information (optic, auditory, etc).
I know this is a weak topic, but I swear to you I've googled this and I couldn't figure out the correct answer and clarification would be greatly appreciated.
Thanks.
Edited by JustinC, : typo

Replies to this message:
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 Message 6 by Doddy, posted 04-30-2007 4:49 AM JustinC has replied

  
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Message 2 of 9 (398159)
04-29-2007 1:24 PM


Thread moved here from the Proposed New Topics forum.

  
Zhimbo
Member (Idle past 6012 days)
Posts: 571
From: New Hampshire, USA
Joined: 07-28-2001


Message 3 of 9 (398163)
04-29-2007 1:35 PM
Reply to: Message 1 by JustinC
04-29-2007 12:58 PM


bundles
They're bundles of fibers.
Some carry different types of information, which is the big clue that they can't be single axons.
I'm looking through my old Kandel and Schwartz and Jessel Principles of Neural Science to check if any of them are single axons, but I don't think so.
Edited by Zhimbo, : No reason given.

This message is a reply to:
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RAZD
Member (Idle past 1405 days)
Posts: 20714
From: the other end of the sidewalk
Joined: 03-14-2004


Message 4 of 9 (398165)
04-29-2007 1:47 PM
Reply to: Message 1 by JustinC
04-29-2007 12:58 PM


are cranial nerves actually bundles of nerves and not just a nerve (singular)?
Example: the optic "nerve" -- this carries the visual information from each eye to the brain, and it is composed of numerous nerves that connect to each singular optic cone or rod.
Optic nerve - Wikipedia
quote:
The optic nerve is the second of twelve paired cranial nerves but is considered to be part of the central nervous system as it is derived from an outpouching of the diencephalon during embryonic development. Consequently, the fibers are covered with myelin produced by oligodendrocytes rather than the Schwann cells of the peripheral nervous system.
and
Page not found - Uveitis.org | OIUF
quote:
The optic nerve is the bundle of over one million nerve fibers that carry visual messages from the retina to the brain.
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JustinC
Member (Idle past 4844 days)
Posts: 624
From: Pittsburgh, PA, USA
Joined: 07-21-2003


Message 5 of 9 (398229)
04-29-2007 9:45 PM


Bundles of nerves...
...just what I thought.
Much thanks Zhimbo and RAZD.

  
Doddy
Member (Idle past 5910 days)
Posts: 563
From: Brisbane, Australia
Joined: 01-04-2007


Message 6 of 9 (398289)
04-30-2007 4:49 AM
Reply to: Message 1 by JustinC
04-29-2007 12:58 PM


are cranial nerves actually bundles of nerves and not just a nerve (singular)?
A nerve simply refers to a bundle of neurons of the PNS (peripheral nerves system). So yes, they are nerves. Even a 'bundle of nerves' is considered a nerve (such as the sciatic nerve, comprised of many nerves of the lower limb).
Anyway, to answer your question further, most cranial nerves split into multiple nerves (such as the vagus nerves, which branch out to most of the viscera). But some, like cranial nerves 0 and 1, are only one pair of nerves for their entirety (that is, both nerves don't split).
Edited by Doddy, : fixed example

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This message is a reply to:
 Message 1 by JustinC, posted 04-29-2007 12:58 PM JustinC has replied

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JustinC
Member (Idle past 4844 days)
Posts: 624
From: Pittsburgh, PA, USA
Joined: 07-21-2003


Message 7 of 9 (398350)
04-30-2007 12:42 PM
Reply to: Message 6 by Doddy
04-30-2007 4:49 AM


So basically a nerve is a bundle of neurons which transmit information to the brain. A neuron is not a nerve. Correct?

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Replies to this message:
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One_Charred_Wing
Member (Idle past 6156 days)
Posts: 690
From: USA West Coast
Joined: 11-21-2003


Message 8 of 9 (398386)
04-30-2007 2:22 PM
Reply to: Message 7 by JustinC
04-30-2007 12:42 PM


Cierto
A neuron isn't a nerve, but rather a building block to a nerve, along with various neurogila.
So... correct.

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Zhimbo
Member (Idle past 6012 days)
Posts: 571
From: New Hampshire, USA
Joined: 07-28-2001


Message 9 of 9 (398392)
04-30-2007 2:59 PM
Reply to: Message 7 by JustinC
04-30-2007 12:42 PM


quote:
A neuron is not a nerve. Correct?
In principle I suppose it could be, although any "nerve" large enough to be named in a mammal or other vertebrate is almost certainly a bundle of axons.
Invertebrates are different - they can have large "nerves" that really are a single axon fiber. In the neurophysiological literature you'll often see talk of the squid giant axon, (which should not be confused with a giant squid's axon!). It's a huge (by cell standards), long axon that was the source of the first measurement of a nerve's action potential.
ABE: OCW makes a good point now that I read him...in vertebrates a nerve will also have glia cells.
Edited by Zhimbo, : No reason given.

This message is a reply to:
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