secondary axis same as primary with different label

I would like to have a secondary y-axis that has the same scale, but a
different label. Also, I would like to draw a dashed line down the
center of the plot.

I have used,

ax1 = pcolor(a, shading='flat', cmap=cm.gray_r)
title('Intensity Pattern')
ylabel('Leaf B')

ylabel('Leaf A')


and the scale is different for the second y-axis as well as prints on
top of the colorbar.


"The game of science can accurately be described as a never-ending
insult to human intelligence." - João Magueijo