▁flow ▁of ▁ ions ▁( ion ▁current ) ▁in ▁bi ological ▁t issues ▁and , ▁in ▁particular , ▁to ▁the ▁elect rical ▁recording ▁techniques ▁that ▁enable ▁the ▁measurement ▁of ▁this ▁flow . ▁Class ical ▁electro phys i ology ▁techniques ▁involve ▁placing ▁electro des ▁into ▁various ▁prepar ations ▁of ▁bi ological ▁t issue . ▁ ▁The ▁principal ▁types ▁of ▁electro des ▁are : ▁▁ ▁simple ▁solid ▁conduct ors , ▁such ▁as ▁disc s ▁and ▁need les ▁( sing les ▁or ▁arrays , ▁often ▁ins ulated ▁except ▁for ▁the ▁tip ), ▁▁ ▁trac ings ▁on ▁printed ▁circuit ▁bo ards ▁or ▁flexible ▁polym ers , ▁also ▁ins ulated ▁except ▁for ▁the ▁tip , ▁and ▁▁ ▁h ollow ▁tub es ▁filled ▁with ▁an ▁electro ly te , ▁such ▁as ▁glass ▁pip ettes ▁filled ▁with ▁pot ass ium ▁ch lor ide ▁solution ▁or ▁another ▁electro ly te ▁solution . ▁ ▁The ▁principal ▁prepar ations ▁include : ▁▁ ▁living ▁organ isms , ▁▁ ▁exc ised ▁t issue ▁( ac ute ▁or ▁cult ured ), ▁▁ ▁dis soci ated ▁cells ▁from ▁exc ised ▁t issue ▁( ac ute ▁or ▁cult ured ), ▁▁ ▁artificial ly ▁grown ▁cells ▁or ▁t issues , ▁or ▁▁ ▁hy br ids ▁of ▁the ▁above . ▁ ▁Ne ur onal ▁electro phys i ology ▁is ▁the ▁study ▁of ▁elect rical ▁properties ▁of ▁bi ological ▁cells ▁and ▁t issues ▁within ▁the ▁nerv ous ▁system . ▁With ▁neur onal ▁electro phys i ology ▁do ctors ▁and ▁special ists ▁can ▁determine ▁how ▁neur onal ▁dis orders ▁happen , ▁by