Biological Systems MCAT Practice Exam

Which type of muscle is characterized as striated and voluntary?

1. Skeletal muscle

2. Cardiac muscle

3. Smooth muscle

4. Multinucleate muscle

The correct answer is: Skeletal muscle

Skeletal muscle is characterized as striated and voluntary. This type of muscle is attached to bones and is responsible for the movement of the skeleton. The striations observed in skeletal muscle are a result of the organized arrangement of actin and myosin filaments, which form repeating units called sarcomeres. This organization allows for efficient muscle contraction when stimulated by the nervous system. The term "voluntary" refers to the fact that skeletal muscle contractions are consciously controlled. This means that individuals can decide when to contract these muscles, such as when lifting an arm or walking. The ability to control these contractions is an essential feature that distinguishes skeletal muscle from other muscle types, such as cardiac or smooth muscle. In contrast, cardiac muscle, while also striated, is involuntary and functions autonomously to pump blood throughout the body. Smooth muscle, on the other hand, is non-striated and also involuntary, typically found in the walls of hollow organs and responsible for involuntary movements such as peristalsis in the digestive tract. The term "multinucleate muscle" does not refer to a specific type of muscle but rather describes the presence of multiple nuclei which is a characteristic of skeletal muscle fibers. Therefore, the defining