Which of the following characteristics is unique to cardiac muscle?

The characteristic that is unique to cardiac muscle is its ability to contract without nervous stimulation. This property is primarily due to the presence of specialized cardiac cells called pacemaker cells, which generate electrical impulses autonomously. This intrinsic ability allows the heart to maintain a rhythmic contraction necessary for pumping blood throughout the body, regardless of external nervous input.

In contrast, skeletal muscle, for instance, requires nervous stimulation to initiate contraction, and smooth muscle can also be influenced by nervous impulses but has its own intrinsic contractile activity. The capacity for regeneration is limited in cardiac muscle when compared to skeletal muscle, which can regenerate more effectively. Additionally, cardiac muscle is involuntary, meaning it operates without conscious control, whereas skeletal muscle is voluntary and can be consciously controlled. The concept of rhythm is also inherent to cardiac muscle, as it continuously beats in a rhythmic manner due to the pacemaker activity.