%   F2_7_VoltageClamp
%   Carol Lucas
%   This routine runs through equations 2.28 and 2.29 for several values of V
%   V is assumed to be a step function that always starts at -60 mV,
%   changes to clamped value at t=10 ms, and returns to -60 mV at 50 ms
%   Yields the graphs shown in Figure 2.7


Vo=-25;So=5;A=10;g=2;Vrev=-65;tstart=0;tend=60;noin=0.0;
k=1;t=[tstart:.5:tend];
clear i;
figure(1);clf;plot([tstart tend],[0 0]);axis([tstart tend 0 200]);
xlabel('time (ms)'),ylabel('current pA');hold on;

for V=-60:5:10
	[t,no]=ode45('vcfun',t,noin,[],V,Vo,So,A);
	i=g*no*(V-Vrev);
	ninf(k)=.5*(1+tanh((V-Vo)/(2*So)));
	tau(k)=A/cosh((V-Vo)/(2*So));
	imax(k)=g*ninf(k)*(V-Vrev);
	figure(1);plot(t,i);text(40,imax(k),strcat('V=',int2str(V)));pause (1);
	Vsave(k)=V;

	k=k+1;
end

input('Hit any key to view voltage dependencies  ');

figure(2);clf;subplot(211);plot(Vsave,imax,'r+-');
xlabel('voltage (mV)'),ylabel('maximum current (pA)');
title('voltage dependencies of current max, tau, and ninf');
subplot(223);plot(Vsave,ninf,'b+-');
xlabel('voltage (mV)'),ylabel('ninf');
subplot(224);plot(Vsave,tau,'g+-');
xlabel('voltage (mV)'),ylabel('tau');pause;