question: Cardiac muscle is found only in which part of the heart?
distractor3: the bottom
distractor1: the ridges
distractor2: the left side
correct_answer: the walls
support: Cardiac muscle is found only in the walls of the heart. When cardiac muscle contracts, the heart beats and pumps blood. Cardiac muscle contains a great many mitochondria, which produce ATP for energy. This helps the heart resist fatigue. Contractions of cardiac muscle are involuntary, like those of smooth muscle. Cardiac muscle, like skeletal muscle, is arranged in bundles, so it appears striated , or striped.