Tuesday, 5 January 2010

Internal anatomy of muscle fibres

  • Sarcomere - The portion of a myofibril between two Z-discs

  • Sarcoplasmic reticulum (SR) - Loose network of flattened tubules that surrounds the myofibrils in the muscle cell

  • Transverse 'T' tubules - Invaginations of the sarcolemma that allow muscle action potentials (electrical chemical impulses) to pass into the centre of the cells causing depoloraization and release of calcium ions from the SR (run over and around the sarcoplasmic reticulum)

  • Terminal Cisternae (lateral sacs) - Expanded regions of the SR, found on both sides of T tubules

  • Calcium ions - concentrated in the SR when muscle fibre is at rest (flood out when muscle contracts)

  • Triad - A T tubule and two terminal cisternae

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