CONFUSED! anesthetics

[MissMedicine]

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Hey guys

so on pg 313 of FA, it says that blockade occurs with small before large and myelinated (autonomic) before unmyelinated (pain). Then they list the order of loss and put unmyelinated before myelinated... i think this (the latter listing) is a mistake

i looked it up in pharm for boards and wards and it says order of loss:

autonomic>pain

anyways FA contradicts itself... any thoughts?

 

[-=UberSharky=-]

Hey guys

so on pg 313 of FA, it says that blockade occurs with small before large and myelinated (autonomic) before unmyelinated (pain). Then they list the order of loss and put unmyelinated before myelinated... i think this (the latter listing) is a mistake

i looked it up in pharm for boards and wards and it says order of loss:

autonomic>pain

anyways FA contradicts itself... any thoughts?

i agree. its a mistake.

 

[StringBean]

Yep, I found that earlier too... it's a mistake.

 

[PSU2002]

Wait a tick,

Wouldn't demyelinated fibers lose sensation first? Or does FA have me totally confused.

 

[nuclearrabbit77]

Hey guys

so on pg 313 of FA, it says that blockade occurs with small before large and myelinated (autonomic) before unmyelinated (pain). Then they list the order of loss and put unmyelinated before myelinated... i think this (the latter listing) is a mistake

i looked it up in pharm for boards and wards and it says order of loss:

autonomic>pain

anyways FA contradicts itself... any thoughts?

..it's not a mistake..just confusing perhaps.

when they say small, they are not saying that the small myelinated autonomic is the same size as the small unmyelinated pain fiber. rather, they are saying that the small myelinated is affected before the large myelinated. (size rule). in addition, pain fibers are actually the smallest size out of all the listed types of nerves. (type IV nerve). again, size factor predominates over the myelination.

hope that helps.

 

[AlexRusso]

I dont have my FA here in NY with me but i think I remember what you're talking about. (Sad how I can close my eyes and picture the page)

Don't they talk about the size being more important than myelination, and to stress this point they say that small umyelinated would be blocked before large myelinated?

 

[MissMedicine]

..it's not a mistake..just confusing perhaps.

when they say small, they are not saying that the small myelinated autonomic is the same size as the small unmyelinated pain fiber. rather, they are saying that the small myelinated is affected before the large myelinated. (size rule). in addition, pain fibers are actually the smallest size out of all the listed types of nerves. (type IV nerve). again, size factor predominates over the myelination.

hope that helps.

Pain fibers are actually smaller than autonomic fibers, it lists them as if they are the same size? is there a reference? Pharm for boards and wards says the order of loss is autonomic then pain.

 

[MissMedicine]

I dont have my FA here in NY with me but i think I remember what you're talking about. (Sad how I can close my eyes and picture the page)

Don't they talk about the size being more important than myelination, and to stress this point they say that small umyelinated would be blocked before large myelinated?

the listing is:
small unmyelinated pain fibers>small myelinated autonomic fibers>large unmyellinated autonomic fibers

its the first part that I am questioning?

 

[nuclearrabbit77]

Pain fibers are actually smaller than autonomic fibers, it lists them as if they are the same size? is there a reference? Pharm for boards and wards says the order of loss is autonomic then pain.

if you have high yield neuroanatomy, or probably most neuroanatomy books.... look at classification of nerve fibers.

well to keep in mind that post-ganglionic sympathetics are unmyelinated...

type IV (C)...diameter .5-1 um ...slow pain, temp, unmyelinated.

versus
preganglionic autonomics(B) <3um ..myelinated preganglionic autonomic fibers.

and the post ganglionic autonomic fibers (C) - 1um....unmyelinated postganglionics..but this one wouldn't apply anyways since we are talking about myelinated vs unmyelinated.






pg. 25 first edition hy neuroanatomy.

http://www.cvm.okstate.edu/Courses/vmed5412/Lect11.htm

here is a table i found on google.

yes, post-ganglionic sympathetic fall under class C but post ganglionics aren't myelinated anyways..