Chapter 17 — Locomotion and Movement

Class 11 Biology Chapter 17 covers locomotion and movement, explaining muscle contraction through the sliding filament theory, the skeletal system's structure (206 bones), and joint types that enable body movement.

Locomotion and Movement is the study of how animals move, from simple protoplasmic streaming in Amoeba to complex coordinated muscular and skeletal activities in humans. The chapter explains three types of human cell movements (amoeboid, ciliary, muscular), the structure of skeletal muscles with their contractile proteins actin and myosin, and the sliding filament theory of muscle contraction. It also covers the human skeletal system comprising the axial skeleton (skull, spine, ribs) and appendicular skeleton (limbs and girdles), and the three joint types (fibrous, cartilaginous, synovial) that enable locomotion. Key muscle properties include excitability, contractility, extensibility, and elasticity, while disorders like myasthenia gravis and osteoporosis affect movement.

1. 01Three types of cellular movements exist in humans: amoeboid (by pseudopodia), ciliary (in trachea and reproductive tract), and muscular (for limbs and locomotion)
2. 02The sarcomere is the functional unit of muscle contraction, composed of thick myosin and thin actin filaments separated by Z lines
3. 03Muscle contraction follows the sliding filament theory: calcium ions trigger actin-myosin cross-bridges, pulling thin filaments over thick filaments to shorten the sarcomere
4. 04The human skeleton has 206 bones: 80 axial (skull, spine, ribs, sternum) and 126 appendicular (limbs and girdles)
5. 05Synovial joints (ball-and-socket, hinge, pivot, gliding, saddle) permit considerable movement unlike fibrous (immobile) and cartilaginous (limited) joints
6. 06Red muscle fibers are rich in myoglobin and mitochondria for aerobic activity; white fibers depend on anaerobic processes and fatigue more easily