This document contains 3 multiple choice questions about muscle cell physiology. The first question asks which protein is activated by depolarization down the T tubule, with the correct answer being the Ryanodine receptor (RyR). The second question asks which structure links myofibrils to the sarcolemma, with the answer being costameres. The third question asks which receptor is blocked by curare, with the answer being postsynaptic nicotinic receptors.