American Society for Clinical Pathology (ASCP) Histotechnologist Practice Test

What unique feature does cardiac muscle have compared to skeletal muscle?

1. Multiple nuclei per cell

2. Involuntary contraction

3. Regeneration capabilities

4. Striated appearance

The correct answer is: Involuntary contraction

Cardiac muscle is distinct from skeletal muscle primarily due to its involuntary contraction capabilities. This means that cardiac muscle functions autonomously, regulating its contractions inherently through the heart's pacemaker cells, such as the sinoatrial node. Unlike skeletal muscle, which is under voluntary control and requires conscious thought for activation, cardiac muscle operates involuntarily to maintain the continuous pumping action required for blood circulation throughout the body. While skeletal muscle is typically associated with voluntary movements and can be consciously controlled, this key difference highlights how cardiac muscle plays a vital role in sustaining life without conscious effort. This characteristic is essential for the consistent and rhythmic contractions of the heart, which are crucial for maintaining effective blood flow and overall physiological balance. In contrast, skeletal muscle is multinucleated and has better regenerative capabilities compared to cardiac muscle, which typically has limited regenerative ability. Although both muscle types exhibit a striated appearance due to their organized contractile fibers, the fundamental difference in their contraction regulation is what sets cardiac muscle apart.