Locomotion and Movement notes

Locomotion and Movement explains how animals and humans change body position, move body parts and perform coordinated actions using muscles, bones and joints. Movement may be amoeboid, ciliary or muscular, while locomotion is movement of the whole organism from one place to another. In humans, skeletal muscles contract by the sliding filament mechanism using actin, myosin, calcium ions and ATP. The skeletal system provides support, protection, mineral storage and attachment sites for muscles. Joints connect bones and allow different degrees of movement, especially synovial joints. The chapter also covers important disorders such as myasthenia gravis, muscular dystrophy, tetany, arthritis, osteoporosis and gout, which are frequently tested in NEET.

Movement is a basic property of living organisms and can occur at cellular, organ or whole-body level. NCERT classifies animal movement mainly into amoeboid, ciliary and muscular movement. Amoeboid movement occurs through temporary cytoplasmic projections called pseudopodia and is seen in Amoeba, macrophages and leucocytes. Ciliary movement occurs through coordinated beating of cilia, such as movement of mucus in the trachea and movement of ovum through the female reproductive tract. Muscular movement depends on contraction of muscle fibres and includes walking, running, breathing, heartbeat and peristalsis. Locomotion is a special type of movement in which the entire organism changes place.

Muscles are specialized tissues that convert chemical energy of ATP into mechanical work. NCERT describes three muscle types: skeletal, smooth and cardiac. Skeletal muscles are striated, voluntary and attached to bones; smooth muscles are non-striated and involuntary; cardiac muscles are striated, involuntary and branched. A skeletal muscle is made of muscle fibres containing myofibrils. Each myofibril has repeating sarcomeres, the functional units of contraction. Sarcomeres contain thin actin filaments and thick myosin filaments arranged into I bands, A bands, H zones and Z lines. According to sliding filament theory, actin slides over myosin using ATP and calcium-regulated cross-bridge cycling, causing sarcomere shortening and muscle contraction.

The skeletal system forms the structural framework of the human body and works with muscles to produce locomotion. Adult humans have 206 bones divided into axial and appendicular skeletons. The axial skeleton has 80 bones and includes the skull, vertebral column, sternum and ribs. It mainly protects the brain, spinal cord and thoracic organs. The appendicular skeleton has 126 bones and includes limb bones along with pectoral and pelvic girdles. Bones provide support, protection, leverage for movement, mineral storage and sites for blood cell formation in marrow. NEET frequently asks direct NCERT facts such as bone numbers, vertebral regions, rib types, limb bones and girdle composition.

Joints are points of contact between bones or between bone and cartilage. They provide stability and determine the range of movement in the skeleton. Structurally, joints are classified into fibrous, cartilaginous and synovial joints. Fibrous joints, such as skull sutures, are immovable. Cartilaginous joints, such as joints between vertebrae, allow limited movement. Synovial joints are freely movable and have a synovial cavity, synovial fluid, articular cartilage, capsule and ligaments. NCERT emphasizes synovial joint types: ball-and-socket, hinge, pivot, gliding, saddle and condyloid joints. Joint movements include flexion, extension, abduction, adduction, rotation and circumduction, which together make locomotion efficient and controlled.

Musculoskeletal disorders affect muscles, bones, joints or neuromuscular transmission and are important NCERT-based NEET topics. Myasthenia gravis is an autoimmune disorder of the neuromuscular junction causing weakness and fatigue of skeletal muscles. Muscular dystrophy refers to inherited progressive degeneration of skeletal muscles. Tetany is rapid muscle spasm due to low calcium ion levels in body fluids. Arthritis is inflammation of joints causing pain, swelling and restricted movement. Osteoporosis is age-related reduction in bone mass, more common in elderly females due to decreased estrogen. Gout is inflammation caused by deposition of uric acid crystals in joints. NEET commonly asks cause, tissue affected and symptoms.