Quick Revision Notes: Class 6 Science

Chapter: Body Movements (शरीर में गति)

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### Introduction

• Movement (गति): A change in the position of a body part while the rest of the body remains at the same place (e.g., waving a hand).
• Locomotion (गमन): Movement from one place to another place (e.g., walking, running, flying).
• Skeleton (कंकाल): The framework of bones inside our body that gives shape and support.

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### Key Concepts & Definitions

• Joints (संधि / जोड़): The places where two or more bones meet in our body. They help in movement.
• Cartilage (उपस्थ): A soft, elastic type of tissue found at the joints between bones. It is not as hard as bones and can be bent.
• Muscle (पेशी): Soft tissues attached to bones that pull them to create movement through contraction and relaxation.
• X-ray (एक्स-रे): A medical imaging technique used to view the shape of bones inside our body.

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### Types of Joints in the Human Body

1. Ball and Socket Joint (कंदुक-खल्लिका संधि):

   • Allows movement in all directions.
   • Example: Shoulder joint and hip joint.

2. Pivot Joint (धुराग्र संधि):

   • Allows us to bend our head forward, backward, and turn it to the right or left. (Up-down and side-to-side rotation).
   • Example: Joint where the neck joins the head.

3. Hinge Joint (हिing / कब्जा संधि):

   • Allows movement only in one direction (like a door hinge).
   • Example: Elbow and knee joints.

4. Fixed Joints (अचल संधि):

   • Bones cannot move at these joints. They are locked tightly together.
   • Example: Bones in the upper jaw and skull.

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### How Muscles Work

• Bones cannot bend or move on their own.
• Muscles work in pairs.
• When one muscle contracts (छोटा और मोटा होता है), it pulls the bone. To move the bone back, the first muscle relaxes and the second muscle contracts.

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### Locomotion in Animals (जंतुओं में चाल)

1. Earthworm (केंचुअ):

   • Does not have bones.
   • Moves by muscles and tiny hair-like structures called bristles (शुकाभ) to grip the ground.
   • Expands and contracts parts of its body alternately.

2. Snail (घोंघा):

   • Moves with the help of a muscular foot.
   • Carries a hard outer shell (कवच) on its back, which is its skeleton, but it does not help in moving.

3. Cockroach (तिलचट्टा):

   • Has a hard outer skeleton (exoskeleton) made of different units joined together.
   • Can walk, climb, and fly using three pairs of legs and two pairs of wings.

4. Birds (पक्षी):

   • Bones are hollow (खोखली) and light, which helps them fly.
   • Hind limbs (legs) are modified for walking and perching.
   • Forelimbs are modified into wings powered by strong flight muscles.

5. Fish (मछली):

   • Has a streamlined body (धारा रेखीय शरीर) that helps it move easily through water.
   • Swims by forming loops alternately to two sides using strong muscles and fins.

6. Snakes (सांप):

   • Slithers (रेंगकर चलना) on the ground by forming loops (वलय) to push against the ground.
   • Has a long backbone and many thin muscles and ribs connected to skin, scales, and bones.

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### Important Points to Remember for Exams

• Human Skeleton: Contains 206 bones in an adult human body.
• Rib Cage (पसलियों का पिंजर): Protects vital internal organs like the heart and lungs.
• Backbone (मेढरदंड / रीढ़ की हड्डी): Made of many small bones called vertebrae (कशेरुक).