IV curve of voltage ramp protocol

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And~'s picture
IV curve of voltage ramp protocol

 Hi all,

I have a naive question if you can help me on this.  When using a gradual voltage ramp protocol (a swipe through a range of voltage), as currents arise through the reverse potential and to opposite direction, will the change in the ionic composition earlier in the ramp of the two chambers affect the subsequent currents recorded in response to a certain voltage, eg. the reverse potential?  So that when the reverse potential or subsequent currents are recorded in a voltage ramp protocol, it would have a chemical ionic gradient different from the chemical gradient initially established across the two chambers?


The FFM's picture
 If you run the ramp fast

 If you run the ramp fast enough, then the change in ionic composition in the cell will not be significant.

The slower the deltaV/delta t the more change there will be a significant effect

And~'s picture
Thx, so it seems to depend on

Thx, so it seems to depend on the significance of ion equilibration.

But what about sustained currents? eg sustained activation of non-desensitising ligand-gated ionic channels, so there should be sufficient time and conductance for equilibration?

and the Nernst equation doesnt take time into consideration i guess, just the balance between opposing electrical and chemical forces, so physiology 101 is maybe a bit misleading since they say 'ions stop diffusing upon encountering an opposing electrical gradient', by that time the chemical gradient has long been changed?

azylbetal's picture
The change in the flow of

The change in the flow of ions start instantaneously, but a non-negligible change in concentration takes some time.