1 - Stimulus excites the neurone cell membrane, causing sodium ion channels to open, so sodium ions diffuse into the neurone, making it less negative. This depolarises the inside of the membrane.2 - Depolarisation - If the potential difference reaches the threshold, more sodium ion channels open so more sodium ions diffuse into the neurone.3 - Repolarisation - Once the potential difference increases so much, the sodium ion channels close and potassium ions channels open, allowing potassium ions to diffuse out of the membrane, reducing the membrane potential.4 - Hyperpolarisation - Potassium ion channels are slow to close so membrane potential becomes more negative than the resting potential.5 - Resting potential - The ion channels are reset, so the sodium-potassium pump returns the membrane to its resting potential.