Giant axon from the squid: Loligo pealei
Hodgkin-Huxley cable equations
Computational implementation of the conceptual model
We could implement this model in Python:
from neuron import h, gui axon = h.Section(name='axon') axon.L = 2e4 axon.diam = 100 axon.nseg = 43 axon.insert('hh')
But for this exercise, let's instead use the CellBuilder tool to create the model:
Save the model in
hhaxon.ses using NEURONMainMenu / File / savesession.
Using the computational model
If starting from a fresh launch of python, you can load the saved ses file by loading NEURON and its GUI:
from neuron import h, gui and then selecting NEURONMainMenu / File / loadsession.
Alternatively you can use NEURON to execute
1. change to the appropriate directory in your terminal
2. Start python, and at the >>> prompt enter the commands
from neuron import h, gui h.load_file('hhaxon.ses')
1) Stimulate with current pulse and see a propagated action potential.
The basic tools you'll need from the NEURON Main Menu :
Tools / Point Processes / Manager / Point Manager to specify stimulation
Graph / Voltage axis and Graph / Shape plot to create graphs of v vs t and v vs x.
Tools / RunControl to run the simulation
Tools / Movie Run to see a smooth evolution of the space plot in time.
2) Change excitability by adjusting sodium channel density.
3) Use two current electrodes to stimulate both ends at the same time.
4) Up to this point, the model has used a very fine spatial grid calculated from the Cell Builder's d_lambda rule.
Change nseg to 15 and see what happens.
NEURON hands-on course
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