The influence of t-system access and luminal resistances upon the conduction velocity of a passively propagated sine wave and associated t-system potential changes. (A) The frequency–velocity relationships for model muscle fibers with: no resistance between the ECF and the t-system lumen (squares); an extremely high access resistance, simulating detubulation (triangles); a physiological t-system access resistance between a single homogenous t-system compartment and the ECF (diamonds); and a physiological t-system access resistance and smaller physiological resistances between each of 20 concentric t-system shells (crosses). Sine waves were driven by a sinusoidal ±300-nA current carried by K⁺ and Cl⁻ ions. (B and C) The underlying changes in E_m (thick lines), E_A (dashed lines), and E_t(0–19) (lighter lines, from E₀, closest to E_m, to E₁₉, furthest from E_m) in the 20-shell t-system model during stimulation at 50 Hz (B) and 1,000 Hz (C). Note that the potential across E_t(0–19) closely tracks E_m at 50 Hz, but lags E_m in both phase and amplitude at 1,000 Hz.