Simulate a model neuron
R, 110 99 bytes

Anonymous function that takes 6 arguments. Nothing fancy, just a straightforward port of the reference implementation. The updating of u, v, and the printing of v have all been combined into a single line, thanks to the fact that R's print returns the value that is being printed, so you can use it in assignment. Many thanks to Giuseppe for saving 11 bytes!

pryr::f({v=c;u=b*c;for(i in 1:t){if(v&gt;=30){v=c;u=u+d}
u=a*b*(v=print((.04*v+6)*v+140+I-u))-a*u+u}})


Try it online!