1 Battle star, an award issued to U.S. Navy ships for participation in battles.  Battlestar (fictional spaceship), a type of spaceship in the original and new television series Battlestar Galactica.
Smooth muscle is fundamentally different from skeletal muscle and cardiac muscle in terms of structure, function, regulation of contraction, and excitation-contraction coupling. Smooth muscle cells known as myocytes, have a fusiform shape and, like striated muscle, can tense and relax.
No. As handsonanatomist mentions it has to do with blood flow to the myocardium(heart muscle itself). The heart muscle itself only receives oxygen during diastole(relaxation), but as heart rate increases the relative length of diastole shortens compared to systole(heart contraction). TLDR; your heart gets tired because it only gets oxygen while relaxed, and the relative amount of time spent relaxing is less.