College of Massage Therapists of British Columbia (CMTBC) Practice Exam

Which type of muscle is primarily responsible for involuntary actions in the body?

1. Skeletal muscle

2. Cardiac muscle

3. Smooth muscle

4. All types of muscle

The correct answer is: Smooth muscle

Smooth muscle is primarily responsible for involuntary actions in the body. This type of muscle is not under conscious control and is found in various internal structures such as blood vessels, the gastrointestinal tract, and the respiratory system. Its involuntary nature allows it to regulate bodily functions automatically, like peristalsis in the digestive system or the constriction of blood vessels. Cardiac muscle, while also involuntary and essential for the heart's function, is specific to the heart itself and is not responsible for the broader range of involuntary actions that smooth muscle performs. Skeletal muscle, on the other hand, is associated with voluntary movements and is under conscious control. Since the question specifically asks for the type of muscle responsible for involuntary actions throughout the body, smooth muscle is the appropriate choice. The option stating "all types of muscle" includes skeletal, which does not perform involuntary actions, thus making it unsuitable as an answer for the question posed.