In one sentence describe how the electricity in an action potential is generated

Due to influx of potassium ions, electricity is generated in axon of a neuron.

Explanation:

Axon membrane is the semi permeable membrane that is full of potassium and sodium channels. There's also Sodium Potassium ATPase pumps. When there's an impulse coming through the synapse, the potassium channels open. This leads to influx of sodium from outside the membrane to inside it. Then the membrane becomes positive.

Then the electricity is generated and its conducted from one part to another. After the impulse is conducted, the sodium potassium pumps come in action which transports 3 sodium inside and 2 potassium outside in consumption to an ATP.