Fig. Both the plasma membrane bounding the cell and inner membranes compartmentalizing its interior space belong to a system of biological membranes -- highly metabolically active trilaminar sheets. It this case, permanganate was used for the tissue fixation which destroyed all cellular constituents except the membranes. Thus the plasma membrane of the nerve cell is apparent (arrow) as well as the membranes of the nucleus (N), endoplasmic reticulum (er) and mitochondria (m). Scale = 1 µm. (Rat, thalamus). Download  the high resolution image.