Which type of muscle is responsible for involuntary contractions in organ systems?

• A. Skeletal muscle
• B. Cardiac muscle
• C. Striated muscle
• D. Smooth muscle

Answer: (D)

Smooth muscle handles involuntary contractions in organ systems. It lines the walls of hollow organs and blood vessels, as well as the bladder, intestines, uterus, and airways. These contractions are not under conscious control; they’re driven by the autonomic nervous system and hormones. Smooth muscle cells are non-striated and spindle-shaped, arranged in layers that allow gradual, sustained squeezing (peristalsis and tone) to move contents along and regulate flow. In contrast, skeletal muscle is voluntary and moves the skeleton, while cardiac muscle is also involuntary but specialized for the heart’s pumping action.