Chapter 8 Body Movements

We can walk, fly, jump, run and can do every possible activity with the help of our body movements.
Body movements are of different types, it may be rotatory, circulatory, oscillatory etc.
With the help of bones and muscles our body can move.
Where two bones are connected at a point, is called joint.
Our shoulder can move in any direction because of the presence of ball and socket points which allows movement of shoulder in all directions.
Pivot joint is present in our neck due to which our neck can move from left to right or can move in forward and backward direction.
Hinge joint is allows movement of body parts only in one direction. It is present in elbow and knee.
Fixed joints are present in skull which cannot move like upper jaw bone; lower jaw bone is exception because it is movable.
A framework of bone called skeleton which gives shape to our body.
Wrist is flexible because it is made up number of small bones of carpel.
Chest bone and backbone together form a rib cage which protects the delicate organ like heart in the chest.
Cartilage is hard but not much hard as compare to the bones. Cartilage is present in our ear and nose.
Muscles helps in the movement of bones by contraction or relaxation.
Earthworm secretes a slimy substance which helps in the movement.
Snail shows very slow movement because movement is done by the muscular feet.

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Exercise 1 ( Page No. : 78 )

Q1	Fill in the blanks: (a) Joints of the bones help in the ——————— of the body. (b) A combination of bones and cartilages forms the _______ of the body. (c) The bones at the elbow are joined by a ______________________ joint. (d) The contraction of the _____________ pulls the bones during movement.
Ans:	(a) Movement It is so because, two bones are connected together with the help of joints. They helps in the movement of the body. (b) Skeleton Bones and cartilage are combine to form a skeleton of the body. (c) Hinge joint Hinge joints are those joints which moves only in one direction. (d) Muscles When the movement occurs, muscles pull and contraction occurs.

Q2	Indicate true (T) and false (F) among the following sentences. (a) The movement and locomotion of all animals is exactly the same. ( ) (b) The cartilages are harder than bones. ( ) (c) The finger bones do not have joints. ( ) (d) The fore arm has two bones. ( ) (e) Cockroaches have an outer skeleton. ( )
Ans:	(a) False It is false because locomotion means movement or displacement of entire body whereas movement is the displacement of entire body or its parts. (b) False It is false statement because cartilage is harder but not as bone. (c) False No, this statement is wrong because due to the presence of joints, our fingers can move. (d) True Yes, it is so because as we know that our forearm has two bones: ulna and radius. (e) True Yes, this statement is correct because as we know that cockroaches have outer skeleton that is made up of number of plates which helps in movement.

Q3	Match the items in Column I with one or more items of Column II. Column I Column II Upper jaw have fins on the body Fish has an outer skeleton Ribs can fly in the air Snail is an immovable joint Cockroach protect the heart shows very slow movement have a streamlined body
Ans:	Column I Column II Upper jaw It is an immovable joint Fish Have fins, have a streamlined body Ribs Protects heart Snail Show very slow movement Cockroach Have an outer skeleton and can fly in air Upper jaw is the skull bone. Lower jaw bone (Mandible) is the only one skull bone which is movable. Fishes have fins, have streamlined body so that they can easily swim in the water. Ribs are very hard and they protect the heart from the injuries or protects other delicate organs inside the chest. Snail shows very slow movement because movement is done by the muscular feet. Cockroaches have outer skeleton, can fly in air. This outer skeleton is made up of number of plates which helps them in the movement.

Q4	Answer the following: (a) What is a ball and socket joint? (b) Which of the skull bones are movable? (c) Why can our elbow not move backwards?
Ans:	Ball and socket joint: It is the type of joint; one bone is like a ball and other one is like a socket, and all is fixed into the socket. This type of joint is called ball and socket joint which is found in shoulders. Such types of joints make movements easy or we can say movements occurs in all directions. Mandible: It is the only skull bone which can move. It is present in the lower jaw which is movable. Our elbow cannot move in the backward direction because in elbow, hinge joint is present which allows the movement of elbow only in one direction.

Chapter 8 Body Movements

Exercise 1 ( Page No. : 78 )

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