Muscle Fibre

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Muscle Fibre

How a Muscle Fibre Shortens

In order to understand the concept behind muscle contraction, it is very important that the muscle structure be known. Muscle is composed of “Actin” filaments and the filaments of “Myosin-II”, which is a protein formed with the help of two polypeptides. Muscles are made up of bundles of fibres that seem similar to a bundle of thins wires held together. These fibres are massive and are formed as a process of the fusion of many cells together. In fact, muscle fibres are multinucleated, which means that a single large cell has many nuclei. The cytoplasm of the muscle fibre is made up of long cylinder-like shaped structures called “Myofibrils”. The contraction and relaxation of muscles is brought about by these “Myofibrils”. (Colliander & Tesch, 1990, pp 31-39)

The muscle contraction for voluntary muscles occurs because of brain signals. Muscle fibres generate tension through the brain signals. The brain sends impulses in the form of “action potential” by way of the nervous system to the motor neuron, which innervates many muscle fibres. Voluntary muscles contraction or shortening is controlled directly by the brain. However, at times, sudden muscle contraction might occur that was not as a result of a brain impulse. This happens in a reflex action when the grey matter of spinal cord sends the signal instead of the brain. (Brooks, Fahey & White, 1996, pp 46-52)

The muscle contraction or the shortening of muscle fibre is a complex procedure. Although the term “contraction” implies shortening, but when referring to a muscular system it refers to the generation of tension by muscle fibres. During the shortening of muscles, a series of events take place. The action of muscles is subjected to the behaviour of “Myosin-II” and “Actin”. It should be understood that during an impulse, it ...
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