What structure does skeletal muscle have? Describe the process of muscle contraction. What role does the central nervous system play in it?

The skeletal muscle has an expanded part – the abdomen and tendons, with which it is attached to bones or other organs such as the skin.
Outside, the muscle is covered with a shell of connective tissue, inside there are muscle fibers collected in bundles – multinucleated cells that are penetrated by blood vessels and nerves. Each muscle fiber contains myofibrils (from the Greek. Myos – muscle), consisting of contractile proteins of myosin and actin.
The contraction of muscle fibers occurs under the influence of nerve impulses coming from motor neurons of the central nervous system. In this case, thinner actin filaments are drawn between the thick filaments of myosin, which leads to the shortening and tension of muscle fibers and, therefore, the entire muscle. For muscle contraction, the presence of Ca2 + ions and ATP molecules, an energy source, is necessary. The coordination of muscle movements in vertebrates, including humans, is carried out by higher motor centers located in the cerebral hemispheres. Thanks to coordination, coordinated work of skeletal muscles is achieved. For example, when contracting the biceps of the shoulder, bending the arm of a person in the elbow joint, the triceps of the shoulder, which performs the function of the extensor of the arm, is relaxed.

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