Example: spike_initiation

Note

You can launch an interactive, editable version of this example without installing any local files using the Binder service (although note that at some times this may be slow or fail to open):

Ball and stick with Na and K channels

from brian2 import *

defaultclock.dt = 0.025*ms

# Morphology
morpho = Soma(30*um)
morpho.axon = Cylinder(diameter=1*um, length=300*um, n=100)

# Channels
gL = 1e-4*siemens/cm**2
EL = -70*mV
ENa = 50*mV
ka = 6*mV
ki = 6*mV
va = -30*mV
vi = -50*mV
EK = -90*mV
vk = -20*mV
kk = 8*mV
eqs = '''
Im = gL*(EL-v)+gNa*m*h*(ENa-v)+gK*n*(EK-v) : amp/meter**2
dm/dt = (minf-m)/(0.3*ms) : 1 # simplified Na channel
dh/dt = (hinf-h)/(3*ms) : 1 # inactivation
dn/dt = (ninf-n)/(5*ms) : 1 # K+
minf = 1/(1+exp((va-v)/ka)) : 1
hinf = 1/(1+exp((v-vi)/ki)) : 1
ninf = 1/(1+exp((vk-v)/kk)) : 1
I : amp (point current)
gNa : siemens/meter**2
gK : siemens/meter**2
'''

neuron = SpatialNeuron(morphology=morpho, model=eqs,
                       Cm=1*uF/cm**2, Ri=100*ohm*cm, method='exponential_euler')
neuron.v = -65*mV
neuron.I = 0*amp
neuron.axon[30*um:60*um].gNa = 700*gL
neuron.axon[30*um:60*um].gK = 700*gL

# Monitors
mon=StateMonitor(neuron, 'v', record=True)

run(1*ms)
neuron.main.I = 0.15*nA
run(50*ms)
neuron.I = 0*amp
run(95*ms, report='text')

plot(mon.t/ms, mon.v[0]/mV, 'r')
plot(mon.t/ms, mon.v[20]/mV, 'g')
plot(mon.t/ms, mon.v[40]/mV, 'b')
plot(mon.t/ms, mon.v[60]/mV, 'k')
plot(mon.t/ms, mon.v[80]/mV, 'y')
xlabel('Time (ms)')
ylabel('v (mV)')
show()