Stimulation of a neuron causes a change in the charge inside the cell from negative to positive. This change is caused by ions, which are atoms with an electrical charge, moving across the cell. This change within the cell is consistent with the definition of an electric charge.
Nerve impulse is a wave of electrical charges that travel along the axon or dendrites of a neurone. a neurone will not transmit an impulse unless the stimulation is strong enough. once the magnitude / size of the stimulation reaches a sufficient level, a full sized impulse is generated to travel the entire length of the axon.
