question related to Hodgkin-Huxley model

Xiaoshen Li xli6 at
Mon Dec 22 10:26:25 EST 2003

Hi Everybody:

I am studying Hodgkin-huxley mechanism and action potentials. I get lost 
in a few *basic*, *simple* questions:

What really is the Action Potential definition? In my work I saw many 
soma spikes. Some peak at
+35mV, some peak at 0mV and some peak at -10mV. They
all have Na channel opens then inactivates, K channel
with a delay opens and closes. The different peaks
they reach I think is due to different percentage of
Na channel be activated and opened. In some conditions
a big portion of Na channel are still in inactivated
status so they cannot be employed in that spike and
they have a lower peak. I am wondering those spikes
with peak at -10mV can be called action potential. If
not, what is the fine line to divide them, since they
all go through the similar AP mechanism.

How to explicitly calculate/predict the threshold of membrane potential 
  which determines to fire an action potential or not? What are the 
factors related to threshold?

Thank you very much for your help. I greatly appreciate it.

Best Regards,

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