Muscles that contract automatically (for example, the heart) are called:

• A. Voluntary Muscles
• B. Cardiac Muscles
• C. Skeletal Muscles
• D. Involuntary Muscles

Answer: (D)

Muscles that contract without you thinking about them are called involuntary muscles. They work automatically, which is why the heart keeps beating and organs like the stomach and intestines squeeze and move without you actively controlling them. The heart is a specific example of a muscle that contracts on its own, thanks to its built‑in pacemaker system and autonomic nerves, but not all involuntary muscles are heart muscle. Skeletal muscles, by contrast, move when you decide to move them, so they’re voluntary.