What type of muscle is found in the heart?

• A. Cardiac muscle, which is involuntary and has lightly striated cells.
• B. Skeletal muscle, voluntary and striated.
• C. Smooth muscle, involuntary and non-striated.
• D. Cardiac muscle, voluntary.

Answer: (A)

The heart muscle is cardiac tissue, which is involuntary and has lightly striated cells. Cardiac fibers are branched and connected by intercalated discs that allow rapid electrical communication and coordinated, rhythmic contractions of the heart. This automatic control comes from pacemaker cells and autonomic input, so you don’t have to consciously move the heart to beat. Skeletal muscle is voluntary and clearly striated, while smooth muscle is involuntary and non-striated, so describing the heart as cardiac muscle that is involuntary with light striations fits best.