Membrane

% Charging and discharging curves for passive membrane patch
%Copyright Minster 2007

clear
% input current
I = 10 % nA

% capacitance and leak resistance

C = 0.1 % nF
R = 100 % M ohms
tau = R*C % = 0.1*100 nF-Mohms = 100*100 pF Mohms = 10 ms
disp(‘(Theoretical)’)

% membrane potential equation dV/dt = – V/RC + I/C

tstop = 150; % ms

V_inf = I*R; % peak V (in mV)
tau = 0; % experimental (ms)

h = 0.2; % ms (step size)

V = 0; % mV
V_trace = [V]; % mV

for t = h:h:tstop

% Euler method: V(t+h) = V(t) + h*dV/dt
V = V +h*(- (V/(R*C))+ (I/C));

% Verify membrane time constant
if (~tau && (V > 0.6321*V_inf))
tau = t
disp(‘(Experimental)’)
end

% Stop current injection
if (t >= 0.6*tstop)
I = 0;
end

V_trace = [V_trace V];
if ~rem(t,10)
plot(0:h:t,V_trace,’r’)
axis([0 tstop 0 V_inf])
drawnow
end

end

hold
Charging and discharging curves for passive membrane patch