What type of muscle is involved in involuntary movements such as those of the heart?

The type of muscle that is responsible for involuntary movements, particularly those of the heart, is cardiac muscle. Cardiac muscle is a specialized type of involuntary striated muscle found exclusively in the heart. It is distinct in its structure and function, allowing the heart to contract rhythmically and pump blood throughout the body without conscious control.

Cardiac muscle cells are interconnected by intercalated discs, which facilitate the rapid transmission of electrical impulses, allowing the heart to beat in a coordinated manner. This characteristic is crucial for maintaining a steady heart rhythm, which is essential for effective circulation.

In contrast, skeletal muscle, which is under voluntary control, is responsible for movements of the skeleton and is connected to bones. Striated muscle refers to skeletal and cardiac muscles, but since the question specifically asks for the muscle involved in the heart's involuntary movements, citing it as a general term does not accurately represent its unique properties. Lastly, voluntary muscle refers to muscles that can be consciously controlled, such as skeletal muscles. This further reinforces that cardiac muscle is the correct answer for involuntary activities related to the heart.