What do muscles do?n Muscles move cows, snakes, worms andhumans. Muscles move you!n You couldnt move anything inside oroutside you. The fact is, without muscles,you wouldnt be alive for very long!
Musclesn Muscles are moved whenever you moven How many muscles do you think there areyour body?n Over 650!n They make up nearly half of your bodyweight.
Musclesn Muscles are bundles of cells and fibresn Muscles are all made of the samematerial, a type of elastic tissue (sort oflike the material in a rubber band).n Thousands, or even tens of thousands, ofsmall fibres make up each muscle.
n You have three different types ofmuscles in your body:n smooth muscle,n Found in the walls of hollow organsn cardiac (say: kar-dee-ak) muscle:n Exists only in your heartn skeletal (say: skeh-luh-tul) muscle.n Produces movement, maintains posture,stabilises joints and generates heat
How do muscles move?n The cells that make up muscles contract andthen relax back to their original size.n Muscles tighten up- CONTRACT and thenRELAXn You have two sets of muscles attached tomany of your bones which allow them to moven They work in pairs
n To bend your arm, one muscle gets shorter andfatter (contracts). It pulls on the bone in thelower arm to which it is attached. At the sametime, the other muscles relaxes, getting longerand thinner.n To move the arm back to where it started, theopposite happens. The relaxed muscle contractsand the other muscle relaxes.n Each of more than 600 muscles is served bynerves which link the muscle to the brain andspinal cord.
n If you take part in lots of exercise whatwill happen to your muscles?n They will get bigger and strongern Muscles are attached to your bones bytendons
n What do you think the biggest muscle is?n The bottomn What about the smallest?n The ear
Voluntary Musclesn Some muscles are known as "voluntary" --that is, they only work when you specificallytell them to.n Can you think of some voluntarymovements?n Clap you hands, lift your leg and so on
Involuntary musclesn Other contracting muscles are automatic.n Can you think of any examples?n Contracting of your heartn the movement of your diaphragm so that youcan breathen blinking your eyes are automatic.n Through signals from your nerves, and, in somecases, your brain, as well.
Factoids!n You have over 30 facial muscles whichcreate looks like surprise, happiness,sadness, and frowning.n Eye muscles are the busiest muscles inthe body. Scientists estimate they maymove more than 100,000 times a day!
Your turn!n In your books, explain the differencebetween involuntary and voluntarymusclesn Explain how muscles move
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