Locomotion and Movement

Human movement depends on a support system made of bones, cartilage, and associated connective tissues. The adult skeleton has 206 bones and is divided into the axial skeleton and appendicular skeleton. Cartilage is flexible and supportive, while bone is hard due to mineral-rich matrix.

NEET usually tests whether you can identify what protects which organ, what belongs to axial vs appendicular skeleton, and how cartilage differs from bone in flexibility and matrix composition.

Joints connect bones and determine the range of motion. Fibrous joints are largely immovable, while synovial joints allow free movement with the help of articular cartilage, synovial fluid, and ligaments. Shoulder is a ball-and-socket joint, elbow is a hinge joint, and atlas-axis gives a pivot type movement.

Three major muscle types are studied here: skeletal, smooth, and cardiac. Skeletal muscle is voluntary and striated, smooth muscle is involuntary and non-striated, and cardiac muscle is striated but involuntary with intercalated discs.

The functional unit of contraction is the sarcomere, lying between two Z-lines. Thin filaments are mainly actin, thick filaments are mainly myosin. The A band, I band, and H zone are favourite NEET testing zones because they change differently during contraction.

Contraction begins when a nerve impulse reaches the neuromuscular junction and triggers calcium release inside the muscle fibre. Calcium binds troponin, shifts tropomyosin, and exposes active sites on actin. Myosin heads then form cross-bridges and use ATP to pull the thin filaments inward.

During contraction, the A band stays constant, while the I band and H zone shorten. That band logic is one of the fastest-scoring parts of the chapter once you stop trying to memorise every line separately.

Important disorders include arthritis, gout, osteoporosis, muscular dystrophy, and myasthenia gravis. Postural defects such as scoliosis, kyphosis, and lordosis are also tested directly.