University:
Western Sydney University
Course:
MEDI 2003 | Clinical Sciences 2
Academic year:

2024
Views:

166

Pages:

2
Author:

Mariam A.

Muscle damage  Skeletal muscle is one of the most adaptable tissues in the body – but at times – the amount of use, metabolic load, or level of stress on a muscle fibre is excessive and causes muscle fibre damage. When this happens, all or part of the muscle fibre degenerates and is subsequently replaced in a process termed regeneration. Clinically, the muscles may experience degeneration following blunt trauma, surgical manipulation, ischaemia and response to the myotoxic effects of local anaesthetics. In addition, when muscle is performing braking actions (e.g. when running downhill), may cause fibre damage due to active muscles being lengthened or stretched forcibly (so-called ‘eccentric’ or ‘pliometric’ contractions) o Common steps in the damage process include a breakdown of Ca2+ homeostasis, elevation of intracellular Ca2+ level, activation of the Ca2+-sensitive proteases and lipases, the breakdown of myofibrillar proteins and membrane lipids, production of free radicals, and in the setting of an accelerated muscle necrosis Normal muscle function  In muscular dystrophies, the connection between the endomysium and action is disrupted and thus causes muscle destruction Chronic degeneration-regeneration scenarios    Muscular dystrophies – heterogeneous group of congenital muscle diseases characterised by severe muscle weakness, and atrophy and destruction of muscle fibres – several genetic defects in muscle transmembrane proteins linking the cytoskeletal protein, e.g. the dystrophin, dystroglycan complex and sarcoglycan complex. Sarcopenia – the process by which the body's lean muscle mass disintegrates over time, loss of strength in older people appears to be directly attributable to physiological and histological changes within the skeletal muscles: Reduction in the number of muscle fibres; Reduction in muscle fibre size; Progressive replacement of the active muscle fibres by collagen-rich non-contractile fibrous tissue; Increased deposition of fat at the expense of lean muscle tissue; Accumulation of lipofuscin (an age-related pigment); Mitochondria within  muscle fibres become less efficient at releasing energy; Reduction in blood flow to muscle groups; and Reduction in motor neuron. The average type II fibre size is diminished with age, whereas the size of type I fibres are much less affected.