Quick Revision Notes: Class 6 Science

Chapter: Body Movements (शरीर में गति)

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.

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.

Ball and Socket Joint (कंदुक-खल्लिका संधि):
- Allows movement in all directions.
- Example: Shoulder joint and hip joint.
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.
Hinge Joint (हिing / कब्जा संधि):
- Allows movement only in one direction (like a door hinge).
- Example: Elbow and knee joints.
Fixed Joints (अचल संधि):
- Bones cannot move at these joints. They are locked tightly together.
- Example: Bones in the upper jaw and skull.

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.

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.
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.
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.
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.
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.
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.

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).