Answer:
The best answer to the question: These cellular structures are utilized in strong involuntary muscle contractions and transmission of electrical impulses, would be: T-Tubules.
Explanation:
In both skeletal and cardiac muscle, not smooth muscle, because of the way that the muscle fibers are conformed into tight bundles of sarcomeres (skeletal muscle) and myocardiocytes (cardiac muscle), there is a need for a series of structures that will ensure that when there is a stimulus from the nervous systems, these stimulus will propagate to all the cells in the fibers, and not just one.
Aside from counting with a neuromuscular motor plate, which will receive the neurotransmitter from the nerve endings and produce the appropriate reactions, as well as propagate that reaction to all the cells that are being stimulated, muscle fibers also have a structure known as T-Tubules. T-Tubules are formations much like roadways of cell plasma membrane that connect not just one, but all the cells within a muscle fiber so that once a stimulus comes, all the cells will initiate the process of calcium release and action potential propagation. These T-Tubules will ensure that electrical impulses reach all muscle cells and that all cells react at the same time as needed.
