What signifies a voluntary muscle?

A voluntary muscle is defined as a muscle that is under conscious control by the individual. This means that the animal can intentionally contract and relax these muscles, allowing for movements such as walking, running, or moving other parts of the body. In contrast, involuntary muscles, such as those found in the heart (cardiac muscle) and the digestive organs (smooth muscle), function without conscious effort, automatically regulating essential processes.

Evaluating the other options, the first choice refers to muscles that are controlled involuntarily, which does not fit the definition of a voluntary muscle. The third option mentions muscles located in the heart, which are specifically cardiac muscles and are not voluntary. The fourth option describes smooth muscles found in digestive organs, which also operate involuntarily. Thus, the distinguishing characteristic of voluntary muscles is their conscious control by the animal.