Q: dendrites/gates

Kalman Rubinson kr4 at nyu.edu
Sun Mar 20 21:49:25 EST 2005


On Mon, 21 Mar 2005 12:27:03 +1100, Matthew Kirkcaldie
<m.kirkcaldie-remove at unsw.edu.au> wrote:

>In article <pk6s31dqj1uk6k2tkkr1cb4lh3qcjts976 at 4ax.com>,
> Kalman Rubinson <kr4 at nyu.edu> wrote:
>
>> Well, technically, the nodes do slow conduction since that is where
>> the time-consuming task of regenerating the AP occurs.  The
>> transmission through the internodal portions of the axon is much
>> faster.  
>
>Splitting hairs here,

Guilty.

> but it's only current which flows through the 
>internodal portions; what the axon is TRANSMITTING is the action 
>potential - since that occurs at the nodes, I don't think you can talk 
>meaningfully about the speed of the internodal regions, since that speed 
>is defined as when the action potential occurs at the next node.

While that definition is true, it is a valid measurement of conduction
speed through the internode.  The point I was poorly making is that
the events at the node are the same as occurs all along an
unmyelinated axon.  It is the elimination of these time-consuming
events (continuous generation of the AP) that makes things speedy.

>The only reason I would come up with such a petty nit-pick is that I 
>often have students who think axons somehow transmit current - whereas 
>of course they actually replicate a triggered event which occurred at 
>the initial segment; current is one of the mechanisms by which the 
>replication is achieved.

Sure.

>I hasten to add that I'm not saying this because I assume you don't know 
>it (which you clearly do) but more for the benefit of anyone reading 
>this thread for edification about neuronal activity!

OK.

Kal (guilty academic)



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