Muscles in the Human Body

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Muscular System


The muscle tissue has four main properties; Excitability, Contractibility, Extensibility and Elasticity.

Excitability; The ability to respond to stimuli.

Contractibility; The ability to contract.

Extensibility; The ability to stretch without causing a tear.

Elasticity; The ability to be able to return to normal shape.

While contraction is taking place the muscular system performs 3 functions; Motion, Heat Production and Maintenance of posture.


The ability of being able to move e.g. walking or running. However, with motion you must know about levers. The framework of the body is covered in muscle which permits movement. When moving or lifting a heavy load, it’s easier to use levers, and in the body it’s the exact same. All levers use 5 different parts; Lever, Fulcrum, Muscle force, Resistive force and Torque.

Lever; almost always the bone

Fulcrum; the pivot point of the lever in which is usually the joint.

Muscle force; the force that drives the opposite ends of the muscles together.

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Resistive force; the force generated by a factor to the external body

Torque; the degree in which a force tends to rotate an object.

There are three different types of levers in the body; First-class, Second-class and Third-class.

First-class; when the muscle force and resistive force is on different sides of the fulcrum e.g. the head resting on the vertebral column. As the head is raised, the facial portion of the skull is the resistance, the fulcrum is between the atlas and occipital bone, and the effort is the contraction of the muscles of the back.

Second-class; when the ...

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