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Skeletal Muscle

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Skeletal Muscle
Animals have three types of muscles; skeletal, smooth, and cardiac. This lab however is only concerned with skeletal muscle. A special characteristic of skeletal muscle is their ability to contract or shorten via thin (actin) and thick (myosin) filaments (Flanagan,2017). This gives a striated appearance which is a key distinguishing characteristic between other types of muscle (Flanagan,2017). Skeletal muscle is also multinucleated. Skeletal muscle needs plentiful amounts of energy to be able to contract, thus having multiple nucleus in each muscle fiber allows for more mitochondria, where the cell gets its power, which increases the amount of useable energy (Flanagan,2017).
There are different types of muscle fibers. These contribute the …show more content…
Within the muscle fiber is the myofibrils or the contractile element. The myofibrils are made up of the myosin or actin proteins that slide past each other during contractions. The sarcomere is the function unit of the muscle. Skeletal muscles contract via motor neurons which conduct action potentials. Action potentials are an all or nothing response, in skeletal muscles this is displayed as a twitch (Holbrook,2017). Fine motor movements have less motor units than large movements (Holbrook,2017). To increase the intensity of the twitch, more motor units can be recruited or increasing the frequency of a twitch causing summation which leads to tetanus …show more content…
onto the postjunctional membrane (LAB). ACh binds to receptors on the cell membrane causing Na+ channels to open and depolarize the cell causing a change in the resting membrane potential (Holbrook,2017). From here Ca2+ is released from the sarcoplasmic reticulum, allowing Ca2+ to bind with troponin on the actin. This undercovers tropomyosin and allows for myosin and actin to bind (Flanagan,2017). When actin and myosin bind, phosphate is released which allows for the myosin head to change shape or power stroke to occur (Flanagan,2017). ATP must come in after the power stoke to provoke the release of myosin from the actin and relax the muscle that was just contracted (Flanagan,2017). Before all this can occur, a stimulus must reach threshold
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