CHAPTER- 5 BODY MOVEMENTS
Notes
1. Many movements continuously occur automatically in our body.
2. We are able to bend or rotate different parts of the body at the places where two parts are joined to each other, for example, the elbow, shoulder, or neck. These places are called joints.
- There are many types of joints in our body for different activities and different kinds of movements.
4. The ball-shaped rounded end of one bone fits into the cup-like cavity of another bone. This type of joint allows movement in all directions.
5. Pivot joint— The joint that connects the head to the neck is a pivot joint.
- With its help, the head can be moved forward and backward or rotated to the right and left.
- In a pivot joint, a cylindrical bone rotates within a ring.
6. There is a hinge joint in the elbow, which allows movement only in one direction—forward and backward.
7. Some joints between the bones of our skull are different from the joints discussed so far. The bones at these joints cannot move; such joints are called immovable joints.
8. Skeleton— All the bones of our body together form a framework that gives the body a proper and well-defined shape. This framework is called the skeleton.
9. X-ray— From an X-ray image, we can see the shape and structure of the bones in our body.
- Many times, when an injury occurs, doctors get an X-ray done, which helps them obtain information about possible damage to the bones.
10. Carpal— The fingers of our hand are made up of many small bones, which are called carpals.
11. Our ribs are specially curved. They join with the chest bone and the backbone to form a box-like structure. This cone-shaped box is called the rib cage.
- There are 12 ribs on each side of the chest. Some important organs of our body are protected inside it.
12. In our body, there is a structure that can be felt starting from the neck and going down the back; it is called the backbone (spinal column). It is made up of many small bones, which are called vertebrae.
- The backbone (spinal column) is made up of 33 vertebrae. The rib cage is also connected to these bones in the chest (thoracic) region.
13. Near the shoulders of a human, two raised bones can be seen; these are called the shoulder bones.
14. Skull— The skull is formed by the joining of many bones. It encloses and protects the brain, which is a very important organ of our body.
15. Cartilage— There are some additional parts of the skeleton that are not as hard as bones and can be bent; these are called cartilage.
16. Muscle— It is responsible for contraction in the body, which enables movement of organs, locomotion, and physical stability.
- While walking or running, you can observe the same kind of contraction in the muscles of your legs.
- In the state of contraction, a muscle becomes shorter, harder, and thicker. It pulls the bone.
17. To produce movement in a bone, two muscles have to work together. When one of the two muscles contracts, the bone is pulled in that direction. The other muscle of the pair relaxes (it becomes longer and thinner).
- A muscle can only pull; it cannot push. Therefore, to move a bone, two muscles must work together.
18. Movement of Animals-
A) Earthworm— An earthworm does not have bones in its body, but it does have muscles.
- While moving, an earthworm keeps the rear part of its body firmly anchored to the ground and stretches out the front part.
- After this, it grips the ground with the front part and releases the rear part. Then it contracts its body and pulls the rear part forward. In this way, it moves forward by a short distance.
- There are many small bristles (hair-like structures) on its body. These bristles are attached to muscles. They help the earthworm get a firm grip in the soil.
B) Snail— There is a round structure on the back of a snail, which is called a shell, and it acts as the snail’s external skeleton.
- This shell is a single unit, and it does not help the snail in movement.
C) Cockroach— It walks on the ground, climbs walls, and can also fly in the air. It has three pairs of legs that help in walking.
- Its body is covered with a hard external skeleton. This external skeleton is made up of different segments joined together by joints, which makes movement possible.
- Two pairs of wings are also attached to the thorax.
- Cockroaches have specialized muscles. The muscles of the legs help them in walking, and the muscles of the thorax move the wings during flight.
D) Birds— Birds are able to fly because their bodies are adapted for flying.
- Their bones have air-filled cavities, which make the bones light yet strong.
- The bones of the forelimbs are modified to form the wings of birds.
- The bones of the chest are specially modified to hold the flight muscles and help in moving the wings up and down.
E) Fish— The head and tail of a fish are thinner and more pointed than its middle part. Such a body shape is called streamlined.
- Because of this special shape, water flows around it and moves away, allowing the fish to swim easily in water.
F) Snake— A snake has a long backbone. The muscles of its body are weak and numerous.
- The muscles also connect the backbone, ribs, and skin with one another.
- A snake’s body is bent into many loops. In this way, each loop of the snake pushes it forward.
- Its body forms many loops, and each loop pushes forward. Because of this, a snake moves forward at a very fast speed, but it does not move in a straight line.
EXERCISE
Question- 1. 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.
Answer- (a) Joints of the bones help in the Movement of the body.
(b) A combination of bones and cartilages forms the Skeleton of the body.
(c) The bones at the elbow are joined by a Hinge joint.
(d) The contraction of the Muscle pulls the bones during movement.
Question- 2. Indicate true (T) and False (F) among the following sentences.
(a) The movement and locomotion of all animals is exactly the same. ( )
(b) The cartilage 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. ( )
Answer- (a)- False, (b)- False, (c)- False, (d)- True, (e)- True.
Question- 3. Match the items in Column 1 with one or more items of Column 2.
Question- 4. 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?
Answer- (a) Ball-and-socket joint– This joint allows the connected parts to move in all directions. Example: shoulder joint.
(b) The lower jaw moves in the skull.
(c) Elbow is an example of a hinge joint, which allows movement in only one direction. Therefore, we cannot move our elbow bac
kward.