Problem
You know that Na/K pumps are a form of active cross-membrane transport of Na and Kions, which means, it takes energy for these pumps to work.
Imagine a situation, where blood flow through a part of the brain gets interrupted due to a blood clot. This part of the brain now does not get blood perfusion, and therefore it gets no oxygen and energy fuel in order to keep the Na/K pumps going in those brain cells. Very soon, these brain cells swell up with water and die.
Explain, how and why the cells swell up (or even burst) if their Na/K pumps stop working.