Code: Select all

```
load_file("nrngui.hoc")
create node[1], myelin[1]
objref nodes, myelins
// topol(nnode) connects an alternating sequence of node/myelin pairs.
proc topol() {local i
nnode = $1
create node[nnode], myelin[nnode-1]
nodes = new SectionList()
myelins = new SectionList()
forsec "node" nodes.append
forsec "myelin" myelins.append
access node[0]
for i=0, nnode-2 {
connect myelin[i](0), node[i](1)
connect node[i+1](0), myelin[i](1)
}
forsec myelins { nseg = 10 }
}
proc geom() {
forsec nodes { // area = 100 um2
L = 3.183
diam = 10
}
forsec myelins {
L = $1
diam = 10
}
}
proc biophys() {local fac
// ohm/cm must be converted to ohm-cm by multiplying by
// cross sectional area
fac = PI*diam^2/4 * 1e-8
forall {
Ra = 100
}
// paper relative to rest=0 but following values relative to -65
forsec nodes {
insert hh
gnabar_hh = 1.2
gkbar_hh = .36
gl_hh = .003
ena = 115 - 65
ek = -12 - 65
cm = 1 // uF/cm2
}
forsec myelins {
insert pas
e_pas = -65
g_pas = 1.5e-6 // S/cm2
cm = 0.005 // uF/cm2
}
celsius = 18.5
}
proc make() {
topol($1)
geom($2)
biophys()
}
make(21, 2000) // appropriate down to 25um internode length
```

Code: Select all

```
load_file("nrngui.hoc")
create node[1], myelin[1], demyel[1]
objref nodes, myelins, demyels
// topol(nnode) connects an alternating sequence of node/myelin pairs.
proc topol() {local i
nnode = $1
create node[2*nnode+1], myelin[nnode], demyel[nnode]
nodes = new SectionList()
myelins = new SectionList()
demyels = new SectionList()
forsec "nodes" nodes.append
forsec "myelin" myelins.append
forsec "demyel" demyels.append
access node[0]
for i=0, 9 {
connect myelin[i](0), node[i](1)
connect node[i+1](0), myelin[i](1)
}
for i=10, 19 {
connect demyel[i-10](0), node[i](1)
connect node[i+1](0), demyel[i-10](1)
}
forsec myelins { nseg = 10 }
forsec demyels { nseg = 10 }
}
proc geom() {
forsec nodes { // area = 100 um2
L = 3.183
diam = 10
}
forsec myelins {
L = $1
diam = 10
}
forsec demyels{
L = $1
diam = 10
}
}
proc biophys() {local fac
// ohm/cm must be converted to ohm-cm by multiplying by
// cross sectional area
fac = PI*diam^2/4 * 1e-8
forall {
Ra = 100
}
// paper relative to rest=0 but following values relative to -65
forsec nodes {
insert hh
gnabar_hh = 1.2
gkbar_hh = .36
gl_hh = .003
ena = 115 - 65
ek = -12 - 65
cm = 1 // uF/cm2
}
forsec myelins {
insert pas
e_pas = -65
g_pas = 1.5e-6 // S/cm2
cm = 0.005 // uF/cm2
}
forsec demyels {
insert pas
e_pas = -65
g_pas = 1.5e-6 // S/cm2
cm = 0.005 // uF/cm2
}
celsius = 18.5
}
proc make() {
topol($1)
geom($2)
biophys()
}
make(10, 2000) // appropriate down to 25um internode length
```

From my understanding, with the current parameters set in the second code, I should get the same results when I graph both codes on the space plot because the first code is one loop, and for the second code I have broken that same one loop into two loops. I hae a nice continuous action potentil for the first code. However, when I graph the second code on the space plot I get a graph that looks like the stimulis has died out in the first myelin compartment, and that also, after I set a much greater current in the IClamp than for the first model. I can't seem to figure out the problem.

I suspect the problem to be here somewhere but I cant pinpoint it:

Code: Select all

```
proc topol() {local i
nnode = $1
create node[2*nnode+1], myelin[nnode], demyel[nnode]
nodes = new SectionList()
myelins = new SectionList()
demyels = new SectionList()
forsec "nodes" nodes.append
forsec "myelin" myelins.append
forsec "demyel" demyels.append
access node[0]
```

Do you think maybe I should be viewing the results of my code with a different kind of graph? By the end, what i think should happend is that when I change the capacitance of demyelin section, I should see a solid action potential through half of the axon modeled and see failure for the second half.

Thanks for all your help!