Biology STAAR (State of Texas Assessments of Academic Readiness) Practice Test

Skeletal muscle is primarily responsible for moving bones in the body. This type of muscle is characterized by its long, cylindrical fibers and striated appearance, which is due to the arrangement of proteins within the muscle cells. Skeletal muscles are attached to bones via tendons and are under voluntary control, allowing for conscious movement, such as walking, running, and lifting.

In contrast, cardiac muscle is found only in the heart and is responsible for pumping blood throughout the body. It operates involuntarily and has a different structure than skeletal muscle, containing intercalated disks that facilitate synchronized contractions.

Involuntary muscle is a broader term that refers to muscles that operate without conscious control, including both cardiac and smooth muscles. Smooth muscle, which is also involuntary, lines organs and blood vessels, controlling processes like digestion and blood flow without direct voluntary movement. These muscle types do not directly facilitate the movement of bones, which is the main function of skeletal muscle.