Muscle contraction, as we know, is the shortening of the muscle fibers. The sarcolemma is the cell membrane of a muscle cell and contains myofibril strands made up of filaments containing ac
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Work:
1) Explain the sliding filament theory/contraction cycling and the major steps of muscle contraction. Note the active fibers, proteins, and substances involved.
Muscle contraction, as we know, is the shortening of the muscle fibers. The sarcolemma is the cell membrane of a muscle cell and contains myofibril strands made up of filaments containing actin and myosin. Actin and myosin have dark and light bands. The A bands are the dark bands, and the I bands are the light bands. At each I band center, a line known as the Z line divides myofibril into smaller sarcomeres. The center of the A band has a region known as the H zone that contains the M line, which holds the myosin filaments parallel. Each sarcomere contains thin actin filaments and thick myosin filaments. The Sliding filament theory shows that when the thick myosin filaments combine with the thin actin filaments, actomyosin is produced, and the filaments slide past each other. The myosin molecules have cross bridges that protrude from the thick filament, and when a muscle is contracted, the actin molecules cross these bridges. Myosin contains ATP sites and enzymes that split the ATP and release energy, and the actin filament contains tropomyosin, which regulates the filament’s function and the interaction between them. The sarcomeres contract by a protein called troponin that binds with calcium ions and moves the tropomyosin away from the binding site on the actin filament. While the filaments slide past each other, it reduces the H zone and pulls the Z lines closer together. The I bands reduce with no change to the A bands.
2) What are the various types of muscle contraction, and what is one example of how we may use each in real life?
Isotonic, isometric, and isokinetic are the three main types of muscle contraction.
Isotonic contractions are where the resistance stays the same, but the muscle length changes and can be broken down into two types, concentric and eccentric contractions. An everyday activity would be lifting weights or conducting a set of push-ups.
Isometric contraction is where there is no change in the length of the muscle while it is contracted. One of the Isometric everyday activities would be planking or holding a plank position.
Isokinetic contractions are contractions where the muscle changes length but produces movements with a constant speed. Running on the treadmill would be an everyday Isokinetic activity.
Classmate question:
Considering recruitment and summation, what roles do you think those methods demonstrate in this discussion?
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