Explain how an action potential is generated

At rest the neuron has a charge of -70mV, this is called the resting membrane potential and is caused by different concentrations of ions inside and out of the cell. At rest, potassium ions accumulate inside the cell as the cell membrane is more permeable to potassium movement than sodium movement.When stimulated, the voltage-gated ion channels open at the synapse, allowing sodium ions into the cell causing depolarisation. Action potentials are an all or nothing event, and the voltage must reach a threshold of -55mV in order to generate an action potential. The action potential in the cell causes the voltage to reach +40mV where the membrane potential is reached and the sodium ion channels close and potassium ion channels open. This is where repolarisation occurs and the cell returns to resting potential.