Tetanic contraction

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Tetanic muscle contraction is a type of muscle contraction which occurs in skeletal muscles, resulting in a stronger prolonged contraction. Tetanic contraction occurs through summation of action potentials travelling into a muscle fibre[1]. As the frequency of the action potentials increases, the muscle has less time to relax and remove the calcium (Ca2+) ions in the sarcoplasm which initiated muscle contraction, through the binding to troponin, causing the myosin binding site to be revealed. Once a given frequency has been reached, the muscle fibre doesn't have time to remove all of the Ca2+ in the sarcoplasm before the next action potential, resulting in Ca2+ remaining in the sarcoplasm. As some Ca2+ remains in the sarcoplasm, when the next action potential arrives, more Ca2+ is released from the sarcoplasmic reticulum, resulting in a higher amount of Ca2+ in the sarcoplasm than in the first action potential. This results in a stronger contraction as more Ca2+ is present, so more myosin binding sites are unveiled, therefore more myosin-actin cross bridges can be formed[2]

References

  1. Muscle Contraction. http://michaeldmann.net/mann14.html (accessed 23/11/16).
  2. Ca2+ Regulation of Muscle Contraction. https://courses.washington.edu/conj/bess/muscle/calciumreg.html (accessed 23/11/16).
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