So is tetany repeated involuntary contractions or just one smooth contraction? If the rate of action potential is rapid wouldn't that give repeated contractions? Also cardiac muscle doesn't have tetany for some reason? Thanks for anyone who can improve my understanding of tetany. Thanks!!Muscle Tetany- is a case of involuntary muscle convulsion. It is a muscular physical state at which action potentials from nerves arrive to the skeletal muscle motor end plate rapidly enough in succession to cause a steady contraction. If the frequency of charge is once per second, the hand muscles (which the ulnar nerve supplies) will flex once per second. If the frequency is increased, the muscle contractions will sum and appear as one smooth contraction. The hand will smoothly close.