Effect of [K+] on membrane and action potential

Tham Seng Choe sengchoe at pobox.org.sg
Fri Aug 22 11:16:53 EST 1997


Hi,

With a rise of extracellular [K+], there would be a lowering of the
membrane potential of an excitable cell (eg neuron or muscle cell). This is
due to the reduction of the "leaking" of K+ from the inside of the cell
through the relatively more permeable K+ channels.

Does this decrease in membrane potential increase the excitability of the
cell? Some of the current views of the above are as follows:

Contrary to what most would think, the decrease in membrane potential,
though causes the cell's potemtial to be "further" than the action
potential, actually makes the cell MORE excitable.

It does so as more of the K+ channels are now closed and this would
decrease the permeability of the cell to K+. With this decrease in
permeability, any slight Na+ influx would be made more significant and this
would lead to the cell being more easily depolarised, and thus being mroe
excitable.

How true is this view? Your comments,please.

Thanks



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