Recording stage
Cell type
Test pulse
Model: the preparation
Pipette & seal
Cell
Channel densities
Amplifier: compensation
Amplifier: recording
Membrane test results
| Parameter | Measured | True |
|---|
How the numbers are obtained
Notes & reference
Test pulse & protocol
Test pulse step: A step from the cell’s own resting potential (either direction), used for the Ra/Rm/Cm measurement exercise. A depolarizing step can recruit Na+/K+ current, which will show up as extra residual in the whole-cell compensation exercise.
Protocol family: A linear family — first, first+increment, first+2×increment, … — for the chosen number of steps. Switching to I-Clamp or V-Clamp resets the protocol to mode-appropriate defaults.
Model: the preparation
Parameters: The true properties of the pipette and cell. In a real experiment these are unknown; the membrane test estimates them.
Pipette transient speed τp: How fast the pipette’s own capacitive transient decays. Unknown in a real experiment, like Cp itself.
Channel densities: Seeded from the selected cell type but freely adjustable. Absolute conductance = density × Cm, so a bigger cell has proportionally bigger currents at the same density.
Setting a density to 0 removes that current entirely (e.g. 4-AP-like A-type block or TTX-like Na+ block).
Amplifier: compensation
Overview: Settings you dial in on the amplifier to cancel capacitive transients. When they match the preparation, the transient disappears and the dials read out the cell’s own values.
C-fast amount: Cancels the size (charge) of the pipette transient. Too much gives an inverted spike.
C-fast speed: Matches how fast the cancellation decays to how fast the real pipette transient decays. A speed mismatch leaves a biphasic (up-then-down) residual at the step edges even if the charge is correct.
Rs compensation: Positive feedback that cancels part of the access-resistance voltage error, speeding up the clamp. Push past ~80 % and the response starts to ring.
Amplifier: recording
Baseline offset: Nulls whatever current is showing right now — same as the amplifier’s Pipette Offset control. Do this with the pipette in the bath, before sealing.
Noise: In V-Clamp this is amplifier/thermal noise added to the recorded current. In I = 0 and I-Clamp the same fluctuating current is injected into the cell, so it shows up as real Vm jitter.
Sweeps averaged: Applies to the Test pulse; the live I = 0 view is simply live. Family sweeps show one noisy trace per step, like a real recording.