Kaplan Nursing Entrance Practice Exam

Which type of muscle is described as involuntary?

1. Skeletal muscle

2. Cardiac muscle

3. Both skeletal and cardiac muscle

4. Voluntary muscle

The correct answer is: Cardiac muscle

Cardiac muscle is classified as involuntary muscle because it operates without conscious control. This type of muscle is found exclusively in the heart and is responsible for pumping blood throughout the body. The heart's rhythmic contractions are regulated by the autonomic nervous system and specialized pacemaker cells, which help maintain a consistent heartbeat without requiring direct input from the brain. On the other hand, skeletal muscle is considered voluntary muscle, as it is under conscious control, allowing individuals to move their limbs and perform various activities intentionally. While some aspects of muscle control, such as reflex actions, can occur without conscious thought, skeletal muscles are primarily activated by voluntary signals from the central nervous system. The choice of "Both skeletal and cardiac muscle" is not accurate because skeletal muscle cannot be classified as involuntary. "Voluntary muscle" cannot be selected as it mischaracterizes the nature of cardiac muscle, which is key in understanding the distinction between these muscle types. Therefore, the correct characterization of cardiac muscle as involuntary reinforces its unique role in the body’s physiology.