alpha-values
\alpha_n(V) = \frac{0.02mV^{-1} (V + 45.7mV)}{1 - \exp(-0.1mV^{-1} (V + 45.7mV))}
\alpha_m(V) = \frac{0.38mV^{-1} (V + 29.7mV)}{1 - \exp(-0.1mV^{-1} (V + 29.7mV))}
\alpha_h(V) = 0.266 \exp(-0.05mV^{-1} (V + 48.0mV))
beta-values
\beta_n(V) = 0.25 \exp(-0.0125mV^{-1} (V + 55.7mV))
\beta_m(V) = 15.2 \exp(-0.0556mV^{-1} (V + 54.7mV))
\beta_h(V) = \frac{3.8}{1 + \exp(-0.1mV^{-1} (V + 18mV))}
time constants
\tau_n(V) = \frac{1.0ms}{\alpha_n(V) + \beta_n(V)}
\tau_m(V) = \frac{1.0ms}{\alpha_m(V) + \beta_m(V)}
\tau_h(V) = \frac{1.0ms}{\alpha_h(V) + \beta_h(V)}
\tau_a(V) = 0.3632ms + \frac{1.158ms}{1.0 + \exp(0.0497mV^{-1} (V + 55.96mV))}
\tau_b(V) = 1.24ms + \frac{2.678ms}{1.0 + \exp(0.0624mV^{-1} (V + 50.0mV))}
