What makes muscles strong?

With every simple move we make our muscle cells are working overtime

Image by Łukasz Dyłka from Pixabay

Moving our limbs seems like a relatively simple task. Whether it’s picking up a cup of tea or taking a walk, the process of movement appears instant and without much thought. However, beneath the skin our skeletal muscle cells are undergoing an extensive process to simply lift a finger.

Skeletal muscles hang on our bones like biological babushka dolls: within each layer of the tissue smaller versions are revealed. At the core of each muscle fibre are rod structures called myofibrils. Within these filaments are two all-important proteins called actin and myosin. It’s their attraction to one another that is responsible for the contracting and relaxing of muscles. However, it’s only after a chain reaction of molecules is released throughout the tissue that the pair are allowed to come to together.

These proteins interact in what is known as the sliding filament model or theory. The actin and myosin, with the aid of released calcium and a molecule called adenosine triphosphate (ATP), contract a section of the myofibrils called the sarcomere. When the calcium and ATP are used up the pair of proteins unbind, releasing the sarcomere from contraction and allowing the muscle to relax. As this cycle continues our muscles are able to animate our bodies. The collective tissue pulls the muscle together, then connective tissue called tendons, which grip the surrounding bone, follow suit. When the muscle contracts the two attached bones are pulled together and thus produce movement.

Inside the muscle

What allows us to move our 640 skeletal muscles?

Click to expand. Image credit: Getty Images/Future PLC

This article was originally published in How It Works issue 122

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