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What job do muscles do?

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What job do muscles do? Muscles are needed for all body movements. Muscles move the bones, julling them into position as they move about their joints. Some muscles just move soft parts of the body, for example, the face muscles that allow you to smile. You can control many of your movements by using voluntary muscles. Other muscles, called involuntary muscles, work automatically to maintain the body. The heart, for instance, beats without your being aware of it. The muscles that squeeze your food along inside the intestines also work automatically.

How are muscles joined to bone?

Muscles are attached to bone by long ropy strands called tendons, which are made of collagen. You can feel these tendons on the inside of your wrist when you flex your hand and fingers.

How are muscles constructed?

Muscles are built up from millions of thread-like cells called muscle fibres.These fibres are gathered into bunches. Nerves instruct the muscle fibres when to shorten, or contract, causing the whole muscle to become shorter in length. The shortened muscle then pulls on the tendon and the bone to which it is joined.

Which are the strongest muscles?

Although it is not very big, the strongest muscle in the body, for its weight, is the masseter muscle in the jaw. It allows you to have a powerful biting action. The largest muscle of all is the gluteus maximus (a Latin name, like many medical terms). It runs from the buttocks down the back of the thigh. The longest muscle is the sartorius, which runs from the hip bone, or pelvis, right down to just below the knee.

What is muscle tone?

Muscles need constant work to keep them strong and healthy. When two muscles work against each other, they will always be slightly contracted and under tension. This is called muscle tone. The fitter you are, the more strongly these muscles will pull against one another, even while you are relaxed.

How do muscle fibres shorten?

Muscle fibres contain tiny rod-like structures that overlap. When the fibre receives a nerve signal that tells it to contract, these rods slide over one another, making the fibre shorter. As the fibres shorten, the whole muscle contracts. All the fibres do not contract together. The harder the muscle needs to pull, the greater the number of fibres that will contract at the same time.

Movement is controlled by the contraction of muscles. Muscles are capable of growing according to the demands placed on them. This is why athletes are so muscular.

Special muscles

The involuntary muscles that automatically keep your body working have a different structure from voluntary muscles. A type of muscle called smooth muscle is mostly found in thin sheets wrapped around internal organs. Smooth muscle contracts quite gently. The bladder, for example, is a balloon-like structure that stores urine until there is sufficient to be discharged from the body. The smooth muscle that covers the bladder then contracts and forces the urine out. Smooth muscle is also present in the iris of the eye.

Can I make my muscles grow?

Muscles react to frequent exercise by growing more muscle cells, or fibres, making the muscle thicker and more bulky. The more fibres there are in a muscle, the stronger it will be. This explains why athletes who take constant exercise develop very large muscles.

The muscles that raise and lower our arms work in pairs.They are called the biceps and triceps. One muscle pulls as the other relaxes, causing the arm to bend or straighten. The biceps muscle that lifts the arm is the stronger of the two.

How many muscles do I have?

You have about 650 muscles in your body. There are more than 50 muscles in your face alone.

Why do many of my muscles work in pairs?

A muscle can only pull in one direction. It needs another muscle to pull in the opposite direction in order to return a bone to its original position.

When you lift your forearm, the biceps muscle shortens to lift the bone. When you straighten your arm, the triceps muscle pulls it back again and the biceps relaxes. The same action takes place in your legs when you walk and run, and when you move your fingers and toes.

What causes muscle cramp?

Cramp is caused by the build-up of a waste substance called lactic acid. When a muscle works harder than usual, it starts to break down stored food without using oxygen. This process is called anaerobic respiration. It produces lactic acid as a waste product. As the lactic acid builds up it interferes with muscle action, making the muscle feel tired, until the acid is flushed away by the blood. If too much lactic acid builds up, it makes the muscle contract very sharply and painfully, causing a cramp.

How does regular exercise help the muscles?

Muscles are able to adapt gradually to the amount of work they have to do, so regular exercise can build them up and make them healthier. Exercise strengthens the muscles and improves muscle tone. It can also improve your body shape and posture, as well as strengthening your heart and improving your blood flow. It will generally make you feel much better and help you to sleep soundly.

Tags: body, muscles, human, health

Category: Education  - ( Education Archive)

Date Added: 21 December '11

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