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# How do I increase the x-axis to make my action potentials bigger

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Nyimatoulie Cham on 20 Oct 2021
Commented: Star Strider on 21 Oct 2021
I_add = 0.1;
tspan = 1000;
v = -65;
m = 0;
n = 0.1;
h = 1;
s0 = [v; m; n; h];
[t1,s1] = ode15s(@hodgkinhuxeqoriginal,[0 tspan], s0, [], I_add);
figure(1)
subplot(2, 2, 1)
plot(t1,s1(:,1));
xlabel('Time');
ylabel('Membrane Potential');
title('Voltage time series');
subplot(2, 2, 2)
plot(t1,s1(:,2));
xlabel('Voltage');
ylabel('m');
title('t vs. m');
subplot(2, 2, 3)
plot(t1,s1(:,3));
xlabel('Voltage');
ylabel('n');
title('t vs. n');
subplot(2, 2, 4)
plot(t1,s1(:,4));
xlabel('Voltage');
ylabel('h');
title('t vs. h');
function dSdt = hodgkinhuxeq(t,s0,I_add)
%Function hodgkinhuxeq
% Inputs: t - time
% I_add - input current
% v - voltage
%potentials
g_k = 36;
g_na = 120;
g_l = 0.3;
E_k = -77;
E_na = 50;
E_l = -54;
Cm = 1;
%variables
v = s0(1);
m = s0(2);
n = s0(3);
h = s0(4);
%eqs
a_m = -0.1*((v+35)/(exp(-0.1*(v+35))-1));
b_m = 4.0*exp((-v-60)/18);
a_h = 0.07*exp(-0.05*(v+60));
b_h = 1/1+exp(-0.1*(v+30));
a_n = -0.01*(v+50)/(exp(-0.1*(v+50))-1);
b_n = 0.125*exp(-0.0125*(v+60));
%dv/dt sections
K_1 = ((g_k*(n^4))*(v-E_k));
Na_1 = (g_na*(m^3)*h)*(v-E_na);
L_1 = g_l*(v-E_l);
%derivat
dVdt = (-1/Cm)*((K_1)+(Na_1)+(L_1)-I_add);
dmdt = a_m*(1-m)-b_m*m;
dhdt = a_h*(1-h)-b_h*h;
dndt = a_n*(1-n)-b_n*n;
dSdt = [dVdt; dmdt; dndt; dhdt];
end
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### Accepted Answer

Star Strider on 20 Oct 2021
The X-limits need to be reduced in order to show the detail, and the last subplot needs to have its axes rescaled to show the detail.
I_add = 0.1;
tspan = 1000;
v = -65;
m = 0;
n = 0.1;
h = 1;
s0 = [v; m; n; h];
% [t1,s1] = ode15s(@hodgkinhuxeqoriginal,[0 tspan], s0, [], I_add);
[t1,s1] = ode15s(@hodgkinhuxeq,[0 tspan], s0, [], I_add);
figure(1)
subplot(2, 2, 1)
plot(t1,s1(:,1));
xlabel('Time');
ylabel('Membrane Potential');
title('Voltage time series');
xlim([0 50])
subplot(2, 2, 2)
plot(t1,s1(:,2));
xlabel('Voltage');
ylabel('m');
title('t vs. m');
xlim([0 50])
subplot(2, 2, 3)
plot(t1,s1(:,3));
xlabel('Voltage');
ylabel('n');
title('t vs. n');
xlim([0 50])
subplot(2, 2, 4)
plot(t1,s1(:,4));
xlabel('Voltage');
ylabel('h');
title('t vs. h');
xlim([0 50])
set(gca, 'XScale','log', 'YScale','log')
function dSdt = hodgkinhuxeq(t,s0,I_add)
%Function hodgkinhuxeq
% Inputs: t - time
% I_add - input current
% v - voltage
%potentials
g_k = 36;
g_na = 120;
g_l = 0.3;
E_k = -77;
E_na = 50;
E_l = -54;
Cm = 1;
%variables
v = s0(1);
m = s0(2);
n = s0(3);
h = s0(4);
%eqs
a_m = -0.1*((v+35)/(exp(-0.1*(v+35))-1));
b_m = 4.0*exp((-v-60)/18);
a_h = 0.07*exp(-0.05*(v+60));
b_h = 1/1+exp(-0.1*(v+30));
a_n = -0.01*(v+50)/(exp(-0.1*(v+50))-1);
b_n = 0.125*exp(-0.0125*(v+60));
%dv/dt sections
K_1 = ((g_k*(n^4))*(v-E_k));
Na_1 = (g_na*(m^3)*h)*(v-E_na);
L_1 = g_l*(v-E_l);
%derivat
dVdt = (-1/Cm)*((K_1)+(Na_1)+(L_1)-I_add);
dmdt = a_m*(1-m)-b_m*m;
dhdt = a_h*(1-h)-b_h*h;
dndt = a_n*(1-n)-b_n*n;
dSdt = [dVdt; dmdt; dndt; dhdt];
end
.
##### 4 CommentsShowHide 3 older comments
Star Strider on 21 Oct 2021
Use the hold function or yyaxis depending on the desired result (the log scales are necessary in order to correctly show ‘h’) —
I_add = 0.1;
tspan = 1000;
v = -65;
m = 0;
n = 0.1;
h = 1;
s0 = [v; m; n; h];
% [t1,s1] = ode15s(@hodgkinhuxeqoriginal,[0 tspan], s0, [], I_add);
[t1,s1] = ode15s(@hodgkinhuxeq,[0 tspan], s0, [], I_add);
figure(1)
subplot(2, 2, 1)
plot(t1,s1(:,1));
xlabel('Time');
ylabel('Membrane Potential');
title('Voltage time series');
xlim([0 50])
subplot(2, 2, 2)
plot(t1,s1(:,2));
xlabel('Voltage');
ylabel('m');
title('t vs. m');
xlim([0 50])
subplot(2, 2, 3)
plot(t1,s1(:,3));
xlabel('Voltage');
ylabel('n');
title('t vs. n');
xlim([0 50])
subplot(2, 2, 4)
plot(t1,s1(:,4));
xlabel('Voltage');
ylabel('h');
title('t vs. h');
xlim([0 50])
set(gca, 'XScale','log', 'YScale','log')
figure
plot(t1,s1(:,4)); % Plot 'h'
hold on
plot(t1,s1(:,2)); % Plot 'm'
hold off
xlabel('Voltage');
% ylabel('h');
% title('t vs. h');
xlim([0 50])
set(gca, 'XScale','log', 'YScale','log')
legend('h','m', 'Location','best') % Add 'legend' Object
title('Using ‘hold’')
figure
yyaxis left
plot(t1,s1(:,4)); % Plot 'h'
ylabel('h')
set(gca, 'YScale','log')
yyaxis right
plot(t1,s1(:,2)); % Plot 'm'
xlabel('Voltage');
ylabel('m');
% title('t vs. h');
xlim([0 50])
set(gca, 'XScale','log')
title('Using ‘yyaxis’')
function dSdt = hodgkinhuxeq(t,s0,I_add)
%Function hodgkinhuxeq
% Inputs: t - time
% I_add - input current
% v - voltage
%potentials
g_k = 36;
g_na = 120;
g_l = 0.3;
E_k = -77;
E_na = 50;
E_l = -54;
Cm = 1;
%variables
v = s0(1);
m = s0(2);
n = s0(3);
h = s0(4);
%eqs
a_m = -0.1*((v+35)/(exp(-0.1*(v+35))-1));
b_m = 4.0*exp((-v-60)/18);
a_h = 0.07*exp(-0.05*(v+60));
b_h = 1/1+exp(-0.1*(v+30));
a_n = -0.01*(v+50)/(exp(-0.1*(v+50))-1);
b_n = 0.125*exp(-0.0125*(v+60));
%dv/dt sections
K_1 = ((g_k*(n^4))*(v-E_k));
Na_1 = (g_na*(m^3)*h)*(v-E_na);
L_1 = g_l*(v-E_l);
%derivat
dVdt = (-1/Cm)*((K_1)+(Na_1)+(L_1)-I_add);
dmdt = a_m*(1-m)-b_m*m;
dhdt = a_h*(1-h)-b_h*h;
dndt = a_n*(1-n)-b_n*n;
dSdt = [dVdt; dmdt; dndt; dhdt];
end
.

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