Math behind section without channels

[mark]

Hi all,

I'm new to NEURON and have a (naive) question regarding a topic which was raised in 2005: viewtopic.php?f=13&t=646

If I want to couple two sections and specify the conductance between them, one way to do so would be to include an artificial section in between (as suggested by Ted):

ted
There are at least two ways to insert a resitance between two sections. One
is to put a third section in between the other two, being careful to make the
dimensions and Ra of the intermediate section such that the desired
resistance is obtained; be sure to set that section's cm to 1e-9.

Now if I do that, how does NEURON handle this artificial compartment without any channels, does it include it into the cable equations as a diff. equation or is it simply treated as a resistance?

Thank you!

[ted]

If I want to couple two sections and specify the conductance between them, one way to do so would be to include an artificial section in between (as suggested by Ted)

"reported" or "described" is a better word here than "suggested", since the former are neutral whereas the latter connotes recommendation or endorsement, and I was certainly not endorsing that particular approach. If your aim is to set up something like gap junction coupling between two sections, linear circuit is preferable. If your aim is to implement a model cell that has two compartments coupled by a user-specified resistance, it's best to just have two compartments coupled by a connect statement, and adjust diameters, lengths, and Ra values to achieve the desired resistance between compartment centers (an approach that I did not mention in that old note).

The answer to your question is that every section has membrane capacitance and, even in the absence of membrane channels, adds at least one differential equation to the system equations.

[mark]

Thank you Ted, you solved my problem! (And you're right about the correction as well).