Which of the following is a primary characteristic of cardiac muscle?

Cardiac muscle is characterized by being striated and involuntary. Striations refer to the alternating light and dark bands visible under a microscope, which is a distinctive feature of cardiac muscle fibers as well as skeletal muscle. However, unlike skeletal muscle, which is under voluntary control, cardiac muscle operates involuntarily, meaning it is not consciously controlled. This involuntary nature ensures that the heart can continuously pump blood without the need for conscious effort.

The properties of cardiac muscle are essential for its role in the body. The striations allow for coordinated contractions required for effective heart function, while the involuntary control ensures that the heart maintains a regular rhythm and responds automatically to physiological demands, such as increased heart rate during exercise. Hence, identifying cardiac muscle as striated and involuntary captures its essential characteristics.