Membrane potential buffering by permeable ions(variable volume)

Membrane potential buffering by permeable ions(variable volume around membrane)

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http://crtzengweb.blogspot.tw/2015/05/membrane-potential-buffering-by.html

When considering if there are variable volume around membrane,
The exact formula derived from Nernst equation becomes below

Voltage of maximal buffering capacity for B+ becomes s=ln(Si/So)/h rather than 0,
Voltage of maximal buffering capacity for A- becomes -s=ln(So/Si)/h rather than 0