How does the cell membrane change in appearance after exposure to the NaCl?
The cell membrane will appear to shrink when a cell is exposed to NaCl.
There are some different ways of interpreting your question, but I'm taking it to mean that you have a cell which is placed into a solution of salt water.
The salt water will cause water to leave the cell - making the cell look like it is shrinking. The movement of water through the membrane (in this case going out of the cell) is called osmosis .
Here is a video which shows this with red onion cells and uses an analogy to help explain the changed in the membrane.
Hope this helps!