AAPC Anatomy Practice Exam

Involuntarily controlled muscles are those that function without conscious effort. This characteristic is crucial in maintaining essential bodily functions. Cardiac and smooth muscle are the two types of involuntary muscle.

Cardiac muscle is found exclusively in the heart and is responsible for pumping blood throughout the body. Its rhythmic contractions are regulated by the heart's pacemaker cells, ensuring that it operates continuously without requiring conscious control.

Smooth muscle, on the other hand, is located in the walls of hollow organs, such as the intestines, blood vessels, and the bladder. It also functions involuntarily to facilitate movements like peristalsis in the digestive system and regulation of blood flow through constriction and dilation of blood vessels.

Skeletal muscle, while it can show striations (hence the term striated muscle), is not involuntary; it is under voluntary control and allows for movements like walking, lifting, and general locomotion.

Since both cardiac and smooth muscle operate involuntarily to serve fundamental physiological functions, the correct choice encompasses both types, making the answer appropriate.