Ephaptic Conduction
<p>Dec 02, 2012 02:13 PM  EPHASIS is GREEK meaning TO TOUCH
 
EPHPTIC coupling...
 
may refer to touching nerves (adjacent)  caused by ion exchange btwn cells or by  local electric fields.
 
can influence synch and timing of action potentials
 
Hx:   late 19th century:  du Bois-Reymond...  firing of a primary nerve may induce firing of adjacent second nerve.
 
explored by Katx and Schmitt in 1940..  confirmed this.
 
attrib to local currents.
 
meachanism and effects
 
role in excit and inhib:  Katz:  ephap coupling is NOT suffic to stim an action potential in
a resting nerve.   Under ideal conditions  maxim depol was 20% of the threshold stimulus.
 
result of ion exchange.   The ACTIVE nerve draws ION STORES from the restin axon...
so, the resting axon exper hyperpol, then depol  etc.  in contrast to the active axon.
 
Role in SYNCH and TIMING:  para 1  not much role
 
para 2:  more recent res:  electric fields.
observ ed that LFP in cortex can serve to synch neurons.
 
hypothes that neurons are ephap coupled to the freq of thelocal field...  effect has been showe and modeled in a variety of cades.  see ref 7 and 8.
 
 </p>