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CBSE Class 06
Science Revision Notes CHAPTER – 8 Body Movements Locomotion: Movement oforganisms from place to place. Locomotion in the human body: (i) Humanskeleton: It forms a framework thatgives shape andsupport to thebody. It consists of 206 bones. It protects internal organs. The humanskeleton has twoparts: 1. The axial skeleton system: It includes the skull, vertebral column and thechest bones orthe rib-cage. 2. Appendicularskeleton system: - It includes shoulder and hipgirdles and thelimbs ( two hands and twolegs ). Bones: - Bone isthe unique combination of flexibility andstiffness. Cartilages: - It is a flexible bonewhich gives support to body parts like ears andnose. It alsoconnects bones together. Tough fibers, the tendons: - Tendons are strong, white cords madefrom collagen. they attach to bones. Collagen: - Bones ina just bornbaby are madefrom soft fibres of a protein called ' collagen '. Ligaments: -Ligaments may bein the formof cords orsheets. (a) Skull: It protects the brain. Itis a rigid box made upof plates ofbone firmly joined together. The skull is bony, forming cranium or the brain-case and the face. Twenty-two smallflat big bonesjoin to formthe skull. Eight flat bonesare fitted together forming a protective box for thebrain. Fourteen bones ofdifferent shapes fusetogether to formthe face. The human skeleton is madeof:
(b) Rib cage: It is a flexible case of ribs. Each rib curves round the sideof the chest from the backbone and is joined in front toa plate ofbone called sternum. Ribs are connected to one another bythe muscles. Twolowermost pairs ofribs are called ‘floating ribs’. (c) Backbone or thevertebral column: Itis also called the spine orvertebral column. (d) Limbs: It ismade up oflong bones withjoints that allow them to move. They are mainly for support. (i)Arms: fore-arms is madeup of twobones and handshave several small bones. Shoulder bones have apair of collarbones in front anda pair ofshoulder blades. (ii)Legs: Lower leg ismade up oftwo bones andfeet have several small bones. Hipbones or griddles bear theweight of thebody and areattached to thigh bones. (iii) Joints: The point where twobones meet. Allow movement to takeplace. Bones areheld together by ligaments. (a) Movable Joints: It allows movement between bonesand has cartilage between them. Type ofmovable joints are: (i)Hinge Joints: It allows movement only in one planebackwards and forwards. Example: elbow joints, kneejoints and thejoint between phalanges of fingers andtoes. (ii) Ball andSocket Joints: It permits a circular movement. Example: theshoulder. (iii) Gliding Joints: It allows bones to slide a little. Example: bones inside wrists and feet. (iv)Pivotal Joints: Joint where theneck joins thehead. It allows the head tomove backwards and forward andturn to theright and left. Backbone is made from 33 rings like pieces. Eachpiece is called a vertebra. It is a chain of small bonescalled vertebrae. It protects the spinal cord,which carries messages between the brainand body. Italso supports theskull, ribs andlimbs.
(b) Immovable or Fixed Joints: The bones cannot move at thesejoints. Example: bones in skull, joint between upper jaw andrest of skull. Locomotion inother animals: (i)Fish: Locomotion achieved by lateral contractions of the muscular body with afinal thrust by thetail. Fish swimby forming loops alternately on twosides of thebody. (ii)Birds: When the large flight muscles contract, they pull thewings down. (iii) Snails: The muscular foot helpsin locomotion. (iv)Earthworms: Move by stretching outthe body in front andkeeping the hindend fixed to the ground. The bones are moved by alternate contractions and relaxation of two sets of muscles. Thebone joints areof various kindsdepending on thenature of joints and direction ofmovement they allow. Strong muscles andlight bones worktogether to helpthe birds fly.They fly byflapping their wings. Snakes slither on the ground by looping sideways. A large number of bones andassociated muscles pushthe body forward. The bodyand legs ofcockroaches have hardcoverings forming anouter skeleton. Themuscles of thebreast connected withthree pairs oflegs and twopairs of wingshelp the cockroach to walk andfly.
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