NCERT Solutions for Class 11 Biology Chapter 17 Locomotion and Movement

Short Note:

• Body movements can be amoeboid (e.g., macrophages, using pseudopodia), ciliary (e.g., movement of ova in fallopian tubes), or muscular (e.g., limb movement, powered by skeletal muscle contraction).

Short Note:

• Skeletal muscle is composed of bundles of muscle fibres; each fibre contains myofibrils made of repeating units called sarcomeres, composed of thin (actin) and thick (myosin) filaments.

• Muscle contraction follows the Sliding Filament Theory: actin filaments slide over myosin filaments (powered by ATP and triggered by Ca²+ ions binding to troponin), shortening the sarcomere without a change in the length of individual filaments.

Short Note:

• The human skeletal system is divided into the axial skeleton (skull, vertebral column, ribs, sternum — 80 bones) and appendicular skeleton (limb bones and girdles — 126 bones), totalling 206 bones.

• Joints facilitate movement, classified as fibrous (immovable, e.g. skull sutures), cartilaginous (slightly movable, e.g. vertebrae), and synovial (freely movable, e.g. ball-and-socket at shoulder/hip, hinge at knee/elbow).