The high resting permeability of the T system to
chloride relative to potassium
means that the resting potential (EM) will be heavily
weighted towards the chloride equilibrium potential (ECl)
which will remain relatively constant during
activity owing to the high [Cl] in the T system
and relatively large amount of Cl in ux needed to
change the [Cl]i
. For this reason, any inward ux of Cl
during the repolarizing phase of an AP has much less
effect on steady-state conditions than would a matching
outward ux of K
on steady-state
conditions
Importantly too, the high Cl permeability of the T system likely aids in recovering some of the K that does build-up in the T system
because if the [K] in the T
system increases sufficiently such that EK across the Tsystem
membrane is less negative than EM
through
conductance
Thus