Body Movements - Science and Tech NCERT Notes for UPSC

Human body and its movements

• Rotates completely (Arm at the shoulder), Rotates partly / turns (Neck), Bends (Arm at Elbow), Lifts (Heel), No movement (Upper Jaw).
• Bones in our body cannot be bent. We can bend or move our body only at those points where bones meet known as Joints.

Following are different types of joints in our body that help us to carry out different movements and activities:

• Ball and socket joints: Such a joint allow movements in all directions.
• Pivotal Joint: The joint where our neck joins the head is a pivotal joint. It allows us to bend our head forward and backward and turn the head to our right or left.
• Hinge joints: Allow back and forth movement like a Door. The elbow has a hinge joint that allows only a back-and-forth movement.
• Fixed joints: Bones cannot move at these joints. E.g., Bones in our head, the joint between the upper jaw and the rest of the head etc.

All the bones in our body form a framework called Skeleton which gives shape to our body. The human skeleton comprises the skull, the backbone, ribs and the breastbone, shoulder and hip bones, and the bones of hands and legs.

• Ribs (bones of the chest) join the chest bone and the backbone together to form a box. This is called the Rib cage.
• The rib cage is joined to a series of bones stretching from the neck to the pelvis known as Backbone (Spine). The backbone consists of 33 vertebrae (individual, interlocking bones).
• Pelvic bones (Pelvis) enclose the portion of our body below the stomach. This is the part we sit on.
• The skull is made up of many bones joined together. It encloses and protects the brain.

Some additional parts of the skeleton that are not as hard as the bones and can also bend are called cartilage. For example, Ear lobes, Nose Tip etc. Cartilage is also found in the joints of the body and act as rubber-like padding.

• Muscle is a soft tissue that can contract and produce motion and force. When contracted, the muscle becomes shorter, stiffer, and thicker. A muscle can only pull. It cannot push. Thus, two muscles must work in pairs to move a bone.

Gait of Animals

• Earthworms:
  • An earthworm does not have bones. It has muscles which help in movement by alternate extension and contraction of the body.
  • Earthworms are known as farmers' best friends since they eat their way through the soil and make the soil more useful for plants. 
• Snail:
  • Move with the help of a muscular foot.
  • Shell (outer skeleton) plays no role in the movement.
• Cockroach:
  The muscles of the breast connected with three pairs of legs and two pairs of wings help the cockroach to walk and fly.

• Birds:
  • Strong muscles and light & hollow bones work together to help the birds fly.
  • They fly by flapping their wings.
• Fish:
  • Fish swim by forming loops alternately on two sides of the body.
  • Streamlined body shape enables water to flow around it easily and allows the fish to move in the water.
• Snakes:
  • Snakes slither on the ground by looping sideways.
  • Many bones and associated muscles push the body forward.

Also Read : What are lab grown diamonds?

Interesting Fact

‘Gait of Animals’ is a book on animal movements by the Greek philosopher Aristotle.

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