The Steps of Muscles contration: the sliding Filament theory, Slides of Health, psychology

Download The Steps of Muscles contration: the sliding Filament theory and more Slides Health, psychology in PDF only on Docsity! he Steps of Muscle intraction: The Sliding aC mle) Yr A Key events that must take place before the contraction of a muscle fiber begins: • SR releases calcium ions into the cytosol • The calcium ions will bind to troponin which causes the troponin-tropomyosin complexes to move away from the myosin binding sites on actin. • Once this happens contraction can begin. • The process is similar to rowing, each myosin head rows forward using the actin as a base to pull from. Step 3: The Powerstroke • Phosphate release by myosin triggers the actual power contraction stroke • ADP pocket opens up on the myosin head • Myosin head rotates and releases the ADP • As the head rotates it moves in a ratchet like motion and pulls the thin filaments closer to the center of the M line of the sarcomere Step 4: Detachment of Myosin • When the ratchet motion is over the myosin awaits another ATP so it can be released from the actin binding site • If an ATP is available the myosin detaches and begins another stroke of the cycle • If not the Myosin remains locked in place and the muscle remains locked up as well this is called “rigor-mortis” Summary Points • Calcium ions are needed to start the cycle • The movement of myosin and actin is like rowers moving across water • Myosin heads will keep binding with actin sites until the ATP runs out or the Calcium levels decrease