Question

What impact would an increase in leak conductance (K+ LEAK CHANNELS) have on the temporal summation of EPSPs? Does this decrease/increase/cause no change in the delta Vm according to a Detla Vm vs. Time plot once the leak conductance is increased? CAPACITANCE IS HELD CONSTANT IN THIS ENTIRE PROBLEM.

Hint: (Think of the Tm=RmCm time constant and how this is affected).

My thought (PLEASE READ): I think this has something to do with the Rm (big Rm), related to the resistance of 1 cm2 of membrane - measured in Ω cm2. Does this change with the increased conductance channels? I know that the big Rm can change depending on the cell size, but idk much about the increased conductance channels...i'd imagine that would make it harder for an EPSP to happen sine current can't flow down the membrane easier?

Answer 1

Answer: EPSP width is most affected when the activation time constant is comparable to the membrane time constant.

The activation time constant of the voltage dependent current is stable in determining the degree to which active currents affect EPSP shape. A relatively slow current is not able to react to voltage transients,. It will simply act as a passive current on the time scale of an EPSP and will decrease
T, 12
and the input current by a factor 1/$\gamma$R. A very fast current is continuously in steady state with the voltage and will therefore effectively acts as a passive current.