Which muscle type is found in the heart and is involuntary, though some control over it can be exerted?

• A. Found in arteries; involuntary
• B. Found in bones; involuntary
• C. Found in the heart; involuntary, but some control is possible
• D. Found in skeletal muscles; voluntary

Answer: (C)

The main idea is identifying the heart’s muscle type and how it’s controlled. The heart is made of cardiac muscle, which is not under conscious control (involuntary) but can be modulated to some extent by the nervous system. Cardiac muscle contracts rhythmically on its own due to intrinsic pacemaker activity, yet sympathetic input can speed the heart and increase force, while parasympathetic input slows it down. This combination—involuntary function with some modulatory control—fits the description perfectly.

The other descriptions point to different muscle types: arteries contain smooth muscle, which is involuntary; bones are associated with skeletal muscle, which is voluntary; and skeletal muscle is the type you actively control. None of those describe a muscle in the heart with the same involuntary-but-modifiable nature as cardiac muscle.