When stimulated, motor neurones propagate an action potential from the spinal cord towards the muscle (Fig 1).

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The neuromuscular junction is juxtaposed between the nerve and muscle and enables communication to occur between the two. This interaction is regulated at cholinergic receptor sites situated in the post-synaptic membrane.

The impulse is then further propagated through the muscle fibres, through a tubule system. Thick filaments slide over thin filaments as the muscle contracts.

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Fig 1 Electical and chemical processes involved in muscle contraction

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Fig 1 Propogation of action potential