Although the contraction of smooth muscle is also regulated by the intracellular concentration of calcium ions, the cell's response is different fr...

Although the contraction of smooth muscle is also regulated by the intracellular concentration of calcium ions, the cell's response is different from that of striated muscles. What is the difference in the response of smooth muscle cells to calcium ions compared to striated muscles?

The calcium ions stored in the sarcoplasmic reticulum are released into the cytoplasm and bind to a protein, calmodulin.
This complex activates an enzyme that phosphorylates myosin and allows it to bind to actin.
The actin and myosin then interact in practically the same way as in striated muscles, resulting in muscle contraction.
The smooth muscle cells have wider T-tubules than skeletal muscle cells.
The smooth muscle cells have a smaller sarcoplasmic reticulum than skeletal muscle cells.
The smooth muscle cells have more limited intracellular reserves of calcium ions than skeletal muscle cells.
Both intracellular and extracellular calcium are involved in cardiac muscle contraction.