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| The importance of Ca2+ has been touched upon with respect to the
Troponin-Tropomyosin
complex. Muscles would remain in a permanent relaxed state if
calcium was not present.
The signal that is passes through the neuromuscular junction into the muscle fiber excites the sarcoplasmic reticulum, which releases Ca2+ into the sarcoplasm. The extensive networking system surrounding the myofibrils controls the regulation of calcium ions. The sarcoplasmic reticulum is a network of interconnected channels that run parallel to the myofibrils. Perpendicular to the sarcoplasmic reticulum is another network called the transverse tubule system (T tubule system). The T tubules are the pathways that deliver the necessary calcium to the myofilaments. After the muscle contraction is over, the calcium is actively transported against the concentration gradient (which requires ATP) back into the sarcoplasmic reticulum. |
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