Muscle Contraction Essay

When it comes to muscle contraction, contraction takes place in the muscle fibers. Muscle fibers are the basic building blocks of the muscle and what allow muscles to contract. They appear as long cylinder cells that contain several nuclei. Contraction happens when the muscle receive signals from the nervous system and the Neuromuscular Junction obtains the muscular exchange where the synaptic bulb and the muscle fibers connect. muscle fibers are composed of myofibrils, which contain contractile units called sarcomeres. Sarcomeres run alongside each other down the length of the myofibril. each sarcomere has alternating thick and thin protein filaments that give skeletal muscle its striated look. muscle contracts takes place when these filaments
Since the actin filaments are attached to the Z lines, the sarcomere shortens from both sides when actin filaments slide along the myosin filaments. the myosin filament pulls the actin along its length and the cross bridges of the myosin filaments attach to the actin filaments and exert the force on them to move. This step is known as the sliding filament theory. The sarcomere shortens without the thick or thin filaments changing in length. Contraction begins when ATP is converted to ADP inorganic phosphate. This causes myosin to extend and attach to a binding site on actin, therefore forming a cross-bridge. After, an action called the power stroke is set off allowing myosin to pull the actin filament toward the M line which will shorten the sarcomere. Myosin stays attached to actin until a new molecule of ATP binds and releases the myosin to go through another cycle of contraction or continue to stay unattached so the muscle can relax. Muscles contractions are regulated by the activity of calcium. The thin filaments deal with troponin and tropomyosin which are regulatory proteins. muscle relaxes, tropomyosin blocks the cross-bridge binding sites on