1. Explain, briefly, why the 10-fold difference in concentration of Na+ across the membrane is important to excitable membranes.

2. How do voltage-gated calcium channels relate to electrical activity of the neuronal vs. sarcolemmal membrane? Concentrate on the differences. Keep your answer brief (3-4 sentences).

3. Why are muscle action potentials only the result of excitation? Think about what hyperpolarization would do for contraction.