Intracellular potentials Extracellular Intracellular Intracellular - PowerPoint PPT Presentation

Intracellular potentials �

Extracellular � Intracellular �

Intracellular microelectrotrode �

Replacing air with KCl in electrodes �

Intracellular microelectrotrode � 0.1 micron � Electrode resistance (10 to 30 Mohms) �

RC response of electrode to current injection � Time constant? �

Electrode capacitance �

Intracellular � Extracellular � direct charge transfer � capacitative charge transfer � DC charge transfer on electrode wire � Conduction in saline solution � Ag + + Cl - � AgCl � Very low solubility � +e - -e - � Conduction in metal � � Ag �

Current injection into cells �

Resting Potential � O mV � What do these have in common? � � “rubbing salt in a wound” � � Lethal injection cocktail � � Dr. Kevorkian’s suicide machine � � Hyperkalemia � � Hypokalemia �

Membrane ion distributions �

Ionic basis of the resting potential � Unequal distribution of ion species across membrane �

Donnan Equilibrium � Selective permeability of ion species through membrane � Loss of K??- Q = CV 10-5 M K for -58 mV �

Squid giant axon- a model prep �

40,000 APs can fire! �

At Rest: INa = IK? � � IK = gK (Vm-EK) INa = gNa (Vm-ENa) � gK (Vm-EK) = gNa (Vm-ENa) �

Other contributions to RP? �

Changes in “ RP” by changing ionic conductances �