What type of event is required for an action potential to be generated?

When the different ions cross the neuron membrane due to this an action potential generated

Explanation:

When the different ions cross the neuron membrane due to this an action potential generated.

The steps for action potential

1. Depolarization. When positively charge sodium ions enters in to the nerve cell. This is also known as upswing.

2. Repolarization

3. Refractory Phase

So the answer is "When the different ions cross the neuron membrane".