Question

Which of the following is true about smooth muscle contraction?

1) Certain smooth muscle cells can actually divide to increase their numbers.
2) Smooth muscle, in contrast to skeletal muscle, cannot synthesize or secrete any connective tissue elements.
3) Smooth muscle cannot stretch as much as skeletal muscle.
4) Smooth muscle has well-developed T tubules at the site of invagination.

Answer 1

True statement about smooth muscle contraction is that certain smooth muscle cells can divide to increase their numbers, a process called hyperplasia. Smooth muscle is unique compared to skeletal muscle, able to sustain contractions when stretched, and produces its own connective tissue.

Step-by-step explanation:

Among the statements provided about smooth muscle contraction, the true statement is that certain smooth muscle cells can actually divide to increase their numbers. This process is known as hyperplasia, which is especially evident in organs like the uterus that increase in size in response to hormones such as estrogen. Smooth muscle has various unique properties when compared to skeletal muscle; contrary to skeletal muscle, it can sustain contractions even when stretched, and its stretch-relaxation response is vital for the function of hollow organs. Unlike skeletal muscle fibers, smooth muscle cells lack T tubules and are not striated because they do not have their filaments arranged in sarcomeres.

They can stretch more than skeletal muscle, and also produce their own connective tissue, namely endomysium. Therefore, options 2, 3, and 4 are incorrect regarding smooth muscle characteristics.Smooth muscle contraction is initiated when calcium ions trigger the binding of calmodulin, which activates an enzyme called myosin kinase. This enzyme phosphorylates myosin heads, allowing them to form cross-bridges with actin and pull on the thin filaments. Smooth muscle can stretch and contract to a greater extent than skeletal muscle, and certain smooth muscle cells can divide to increase their numbers.