Muscles can be made up of 3 types of cells: skeletal, smooth, …show more content…
Skeletal muscle cells have what is known as striations or stripe like appearance of the cell body. Skeletal muscle cells are multinucleated often because of their large size another distinction of muscle fibers. Skeletal muscle cells have a significant number of mitochondria this is a result of the large amount of energy that muscle contraction and movement use. Muscles build together much like cable or rope, muscles can be separated into bundles of fascicles and fascicles can be separated into bundles of muscles fibers and finally muscle fibers can be separated into bundles of myofibrils, which are another unique structure of skeletal muscle cells. This bundling allows muscles to have great strength in their …show more content…
The SR is extensive and covering all the myofibrils this allows fine control of contractions of the myofibrils due to depolarization only affecting the targeted areas since the SR release of calcium ions is the key to muscle contraction. Myofibrils are protein bundles containing actin and myosin. Actin (thin) and myosin (thick) make up a unit of skeletal muscle cell called a sarcomere, the main unit of contraction in skeletal muscle cells. The patterns of sarcomeres make up the striations or the stripe like feature of the cell. The actin and myosin in the sarcomere use what is known as the sliding filament theory as means of causing the contractions of muscle. Myosin slides along actin filaments to contract a sarcomere as the number of sarcomeres contracting increases the muscle contracts stronger and stronger vice-versa as more sarcomeres relax the muscle contraction grows weaker and weaker. A sarcomere contraction can only occur when calcium ions from the SR that are released by action potentials from nerve fibers bind to the protein troponin that is associated with tropomyosin this calcium binding