Muscular System

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What is the role of muscle?In order to make the joints move, muscles are required.The muscles in the body can pull.Combined with the joints, this allows us to move.

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We need to know the names of

some of the muscles so, here goes!

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Biceps

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Pectorals

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Deltoids

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Abdominals

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Quadriceps

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Trapezius

And at the back!

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Deltoids

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Triceps

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Latissimus dorsi

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Gluteals

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Hamstrings

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Gastrocnemius

Also known as calf

muscles

16Gastrocnemius

So, in summary, all the muscles that you need to know which are visible from the back are:

HamstringsGluteals

Latissimus dorsi

TricepsDeltoidsTrapezius

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And, in summary, all the muscles that you need to know which are visible from the front are:

BicepsPectoralsDeltoids

AbdominalsQuadriceps

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There are three different types of muscle:

•Cardiac muscle

•Involuntary muscle

•Voluntary muscle

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There are three different types of muscle:

•Cardiac muscleCardiac muscle is only found in the heart.Without any conscious effort, it repeatedly contracts and then relaxes throughout your life.

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There are three different types of muscle:

•Involuntary muscleThese muscles also work without any conscious effort.However, they do not work continuously.They are found around organs such as the intestines and blood vessels.

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There are three different types of muscle:

•Voluntary muscleVoluntary muscles are under your own control.They are attached to your skeleton.

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How do muscles pull bones?For a muscle to pull successfully, it must be attached to two bones which are pivoted about a point.

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How do muscles pull bones?For a muscle to pull successfully, it must be attached to two bones which are pivoted about a point.Here the muscle in red pulls inwards with forces applied to the shoulder and forearm as indicated by the blue arrows.

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How do muscles pull bones?

Notice the pivot point

The muscles are attached to the bones by tendons.The tendons will attach each muscle to two bones.One bone will be fixed so that as the muscle pulls, the other bone moves.

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How do muscles pull bones?The point where the muscle is attached to the stationary bone is called the origin.

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How do muscles pull bones?The point where the muscle is attached to the bone that moves is called the insertion.

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How do muscles pull bones?Here, we are looking at how the biceps are used to raise the forearm.There is, of course, the problem of lowering the forearm.We have said that muscles only pull and clearly, the biceps’ pull only raises the forearm!

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How do muscles pull bones?This is the job of the triceps which are attached to the forearm on the other side of the pivot.If the triceps pull, the forearm is lowered.

Biceps

Triceps

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How do muscles pull bones?This is the job of the triceps which are attached to the forearm on the other side of the pivot.If the triceps pull, the forearm is lowered.

Biceps

Triceps

What we have actually done here is described how muscles work in pairs. These pairs of muscles are called antagonistic muscles.

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How do muscles pull bones?

Biceps

Triceps

Antagonistic musclesAs one of the muscles pulls (contracts), the other one relaxes (extends). In this case the triceps pull as the biceps relax.

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How do muscles pull bones?

Biceps

Triceps

Antagonistic musclesThe relaxing muscles, the antagonists, in this case, are the biceps.

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How do muscles pull bones?

Biceps

Triceps

Antagonistic musclesThe contracting muscle which is pulling is called the prime mover. It is the one that is causing the motion!Another name for the prime mover is the agonist.

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How do muscles pull bones?

Biceps

Triceps

Antagonistic musclesIt is, of course, essential that the shoulder remains stationary.This is achieved using special muscles called synergist muscles.

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How do muscles pull?

If a muscle contracts, it is easy to see that it will make something move (provided that one end of it remains fixed in position).This is called isotonic contraction.Any exercise that makes a part of the body move is caused by isotonic contraction.

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How do muscles pull?

However, muscles are used without movement occurring.In this case, there cannot be contraction of the muscle – otherwise there would be movement!This is called isometric contraction.

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Do all muscles do the same thing?No, there are two types of muscle fibres which behave in different ways.Fast twitch muscles will contract very quickly and with great force. They are powerful muscles.However, they tire very quickly.Sprinters will have many, well-developed fast twitch muscles. They need to be able to do work quickly for short periods of time.

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Do all muscles do the same thing?No, there are two types of muscle fibres which behave in different ways.Slow twitch muscles will contract more slowly and with less force. They are less powerful muscles.However, they don’t tire so quickly.Long distance runners and cross country skiers will have well-developed slow twitch fibres to give them stamina.