Figure 6.

Schematic of an action potential, showing the variation of the membrane voltage, V_m, at a single location as a function of time. A stimulus of various magnitudes applied at the time indicated by the arrow triggers a response that is dependent on the magnitude of the stimulus. A small stimulus (purple) results in a small membrane depolarisation that rapidly returns to the resting potential (v_rest, dashed). A large stimulus (red) is sufficient to trigger Cl⁻ channels that result in a large membrane depolarisation (the action potential). The initial depolarising stimulus must be greater than some threshold value, v_T, (indicated by the grey line) to trigger the Cl⁻ channels and cause the development of the action potential. The action potential is an all or nothing response, any supra-threshold stimuli will result in the same action potential response.