A patch pipette with configurable geometrical properties.
Normally one need only set the resistance, tipDiamater and solution in the pipette. At the advanced user level (see the control parameters) there are several other quantities accessible. The stimResistance is the resistance between the wire core and the solution filling the body of the pipette. This is important as it controls the time-course of charging the pipette capacitance. The latter is governed by the shaftArea and the shaftCspec - shaft specific capacitance. The area here is the the surface area of glass immersed in the bath solution which makes up the pipette capacitance. Either of these quantities may be set to zero to eliminate capacitance transients from the pipette. Note that setting the stimResistance very low reduces the time course of the transient but increases its magnitude, generally appearing as a stimulus artifact in a recording. Unlike certain hardware spatch does not compensate for capacitance transients: if you do not want to see them, then you must make a model which does not have them.
When computed, each pipette is modeled as a three component system: the core, which is voltage or current clamped by a controller; the main fluid volume filling the pipette, and the tiny fluid volume just inside the tip. The pipette resistance goes between the main volume and the tip volume, and the surface capacitance between the main volume and the bath.
The desired patch configuration can also be set here (config at user level "advanced"), although it is normally set from the bath editor. It is one of - cell-attached, whole-cell, inside-out and outside-out.