Can an electric shock cause loss of consciousness?

Yes it can. It depends on the amount of voltage that you got shocked with.

Electric shock can put the heart into asystole (absence of heart contractions). The heart will often resume its rhythm, but the accomanying respiratory arrest lasts longer, and can then lead to a second cardiac arrest due to lack of oxygen.

Also, all electrical burns are considered to be worse than look externally (they can burn internally as well).