Question

In smooth muscle, thin actin filaments attach to which of the following?

1) Thick myosin filaments
2) Intermediate filaments
3) Dense bodies
4) Z discs

Answer 1

In smooth muscle, thin actin filaments attach to dense bodies, which are similar to Z-discs in skeletal muscles and act as anchors for contraction.

Step-by-step explanation:

In smooth muscle, thin actin filaments attach to dense bodies. These dense bodies are analogous to the Z-discs found in skeletal and cardiac muscle fibers, serving a similar role in anchoring the thin filaments that are indispensable for muscle contraction. Unlike skeletal muscles, smooth muscles do not possess Z-discs but have dense bodies that connect to the sarcolemma. During contraction, calcium ions interact with calmodulin, leading to the activation of myosin heads and the pulling of thin filaments. The pulling action of these filaments on the dense bodies results in the contraction of the smooth muscle fiber, often leading to a corkscrew motion.