Final answer:
Muscle cells exhibit striations due to the organization of actin and myosin. Skeletal muscles are multinucleated and enable voluntary movement, while cardiac muscles contract as a unit to pump blood. The sliding filament theory explains muscle contraction.
Step-by-step explanation:
There are indeed striations across the width of muscle cells, specifically in skeletal and cardiac muscles. These striations are created by the regular arrangement of the contractile proteins actin and myosin. Skeletal muscle fibers are multinucleated with the nuclei situated on the periphery of the cell. These fibers are long tubular cells that enable voluntary movement. Cardiac muscle fibers have one to two nuclei and are connected in a way that allows the heart to contract as a unified organ. The functional units of muscle tissue are sarcomeres, which shorten during muscle contractions, allowing the thick and thin filaments to slide across each other according to the sliding filament theory. This movement facilitates muscle contraction, with ATP energizing the process. Differences in fibers, such as slow-twitch and fast-twitch fibers in skeletal muscles, contribute to varying responses to exercise, impacting how muscles grow or shrink. The structure and function of muscle tissues are closely related; their specializations allow controlled contraction for voluntary and involuntary movements, vital to physical and mental health.