Electric current propagation through living tissue

[Jacekmai]

Wave propagation speed or velocity of propagation (VoP) of a transmission medium is ratio at which the wavefront of the signal passes through the medium to the speed of light in vacuum. For example, copper has a wave propagation speed ~0.951.

What is a wave propagation speed through a living tissue such as for example, muscle, liver or brain?

Flesh and biological tissue in general are heterogeneous. So one can assume that in this case current propagates through the movement of ions and charged molecules resulting in low conductivity. To avoid discussion of nonlinear effects such as carbonization etc., let us use as an example, an electrocution event at moderate current densities (low electrical field). Most probably we must take under consideration some (micro) capacitances and perhaps inductances (?) to account for the effect?

Anyone knew the range of VoP values for living tissue? References?

 

[thankz]

http://openwetware.org/wiki/Lab_9:_...s#Conduction_Velocity_in_a_Frog_Sciatic_Nerve
https://en.wikipedia.org/wiki/Action_potential
http://neuroscience.uth.tmc.edu/s1/chapter03.html

edit: think of it as an RC time constant in the shape of a reverse saw wave mixed with propagation delay as ion channels in the nodes fluctuate.

 

[Jacekmai]

http://openwetware.org/wiki/Lab_9:_...s#Conduction_Velocity_in_a_Frog_Sciatic_Nerve
https://en.wikipedia.org/wiki/Action_potential
http://neuroscience.uth.tmc.edu/s1/chapter03.html

edit: think of it as an RC time constant in the shape of a reverse saw wave mixed with propagation delay as ion channels in the nodes fluctuate.

You are right as far as a speed of nerve response to a small voltage, but it is not a situation I was interested in.

I am trying to understand a situation where we force through a tissue a relatively large current compared to the current internally generated by nerve or neurons in response to small stimuli . So in the situation where you apply voltage and force the flow to through for example liver we may not observe a large current due to the nerve conductivity. In the situation of brain electrocution (with low current) there may indeed be a contribution from current from neurons but still the majority may be from the paths through blood arteries and veins and .celebrospinal fluids. I asked the question because I could not find reference discussing the contributions from different paths a moderate current could take in the tissue in the presence of external voltage (electrical field). I guess in the case of brain it is not simple to measure the flow and keep the subject alive ;-)

 

[thankz]

https://en.wikipedia.org/wiki/Goldman_equation
http://www.ncbi.nlm.nih.gov/books/NBK21668/

maybe you can make sense of the math but you might be able to figure out the limit when a high enough voltage causes a complete flooding of the cytosol? (K+), but I'm not really sure of which direction. my books are packed up for the most part( i'd have to dig through at least 3 to find the answer) so this is as far as I go for now.