Answer:
For the compacting of a vertebrate skeletal muscle fibre to occur, the reactions go on in the body:
i. the body's motor neuron triggers the neurotransmitter which in turn leads to a release of calcium ions
ii. the Calcium ions bonds to a regulatory protein called Troponin. When this bonding occurs the protein mentioned above attracts another type of protein called tropomyosin away from the binding sites on actin filaments.
Actin filaments are found in muscle and nonmuscle cells as microfilaments in the cytoskeleton and as thin filaments in the body's contractile system.
iii. the Myosin cross bridges bind themselves to actin filaments
iv. The cross bridges then attract actin inward by bending
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