Chapter 17 | Locomotion and Movement | Class 11 Biology | NEET | Iyal.App
🔬 Movement vs Locomotion: Movement is a fundamental feature of all living organisms. Locomotion specifically refers to voluntary movements that cause a change in place or location (walking, running, swimming, flying).
🏆 Why Animals Move: Animals engage in locomotion to search for food, find shelter, locate mates, discover breeding grounds, escape predators, and move to favorable climatic conditions.
📚 Three Types of Cellular Movement: Human cells exhibit amoeboid movement (macrophages, leucocytes using pseudopodia), ciliary movement (coordinated beating in trachea and reproductive tract), and muscular movement (contraction of muscles for locomotion).
🔬 Muscle Types: The body has three muscle types - Skeletal muscles (striated, voluntary, for locomotion), Visceral muscles (smooth, involuntary, in internal organs), and Cardiac muscles (striated, involuntary, heart muscles).
🏆 Muscle Structure: Muscles are organized hierarchically - bundles (fascicles) contain fibers, fibers contain myofibrils, and myofibrils contain sarcomeres (the functional unit of contraction bounded by Z-lines).
📚 Contractile Proteins: Thin filaments are made of actin with regulatory proteins troponin and tropomyosin. Thick filaments are made of myosin with globular heads that have ATPase activity and bind to actin.
🔬 Sliding Filament Theory: Muscle contraction occurs when thin filaments slide over thick filaments (filaments don't shorten). This is powered by ATP and regulated by calcium ions.
🏆 Contraction Mechanism: Neural signals trigger Ca++ release from sarcoplasmic reticulum → Ca++ binds troponin → exposes myosin binding sites on actin → cross-bridges form → power stroke pulls actin filaments → sarcomere shortens.
📚 Red vs White Fibers: Red fibers contain high myoglobin, many mitochondria, use aerobic metabolism, and sustain contractions (posture, endurance). White fibers have low myoglobin, fewer mitochondria, use anaerobic metabolism, and fatigue quickly (sprinting, jumping).
🔬 Skeletal System: The human skeleton has 206 bones organized into axial skeleton (80 bones: skull, vertebrae, ribs, sternum) and appendicular skeleton (126 bones: limbs and girdles).
🏆 Joints Classification: Fibrous joints allow no movement (skull sutures), cartilaginous joints allow limited movement (intervertebral discs), and synovial joints allow considerable movement (shoulder, knee, hip).
📚 Common Disorders: Myasthenia gravis (autoimmune attack on neuromuscular junction), Muscular dystrophy (genetic muscle degeneration), Tetany (low calcium causing spasms), Arthritis (joint inflammation), and Osteoporosis (decreased bone mass, common in postmenopausal women).
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