Found only in the heart and is involuntary?

Found only in the heart and is involuntary?

• A. Skeletal muscle
• B. Smooth muscle
• C. Tendons
• D. Cardiac muscle

Answer: (D)

Cardiac muscle is the heart’s muscle tissue. It’s found only in the heart and its contractions happen without conscious control, making it involuntary. Cardiac fibers are striated like skeletal muscle but are branched and linked by intercalated discs with gap junctions, which coordinate a rapid, synchronized beat. The heart’s rhythm is set by intrinsic pacemaker activity and modulated by the autonomic nervous system, not by voluntary effort. Skeletal muscle is voluntary and attached to bones; smooth muscle is involuntary but located in walls of hollow organs and vessels (not in the heart); tendons are connective tissue, not muscle. So the correct choice is cardiac muscle because it uniquely resides in the heart and functions involuntarily.

Cardiac muscle is the heart’s muscle tissue. It’s found only in the heart and its contractions happen without conscious control, making it involuntary. Cardiac fibers are striated like skeletal muscle but are branched and linked by intercalated discs with gap junctions, which coordinate a rapid, synchronized beat. The heart’s rhythm is set by intrinsic pacemaker activity and modulated by the autonomic nervous system, not by voluntary effort. Skeletal muscle is voluntary and attached to bones; smooth muscle is involuntary but located in walls of hollow organs and vessels (not in the heart); tendons are connective tissue, not muscle. So the correct choice is cardiac muscle because it uniquely resides in the heart and functions involuntarily.