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Delve into the intricate world of muscles with a focus on anatomy, function, and biomechanics. Understand the importance of muscle movement in body processes and the topological organization of muscles. Learn about different muscle fiber types and auxiliary structures that support muscle function. Explore the histological characteristics of muscle fibers and the theory of sliding myofilaments in muscle contraction. Gain insights into the science behind muscle biomechanics and the cycle of crossed bridges. Discover the secrets behind muscle strength and how muscles interact with joints through synergists and antagonists. Enhanced with detailed illustrations, this comprehensive guide is a must-read for fitness enthusiasts, students, and anyone intrigued by the fascinating world of muscles.
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Science of muscle Stefan Sivkov MU - Plovdiv
Why do we study muscles? • Body movement • Skeletal movement • Movement of blood • Movement of food • Uterine contractions
Muscle disorders • Food resource • Weight control • Use it or looseit
General characteristics • 600 muscles - 40 % body weight • Organ structure • muscle, connective, nerve, epithelialtissue • Functions • movement • heat production • posture control • support
Embryogenesis Mesodermal origin • Somites – primary mesodermal segments • sclerotomes – vertebral column • myotomes – muscles of body and limbs • dorsal – back muscles • ventral – antero-lateral and limb muscles • Branchial gills – facial and neck muscles
Topological organization of muscles • Paired and symmetrical • Segmental – in the body • Shortest distance between origin and insertion • Perpendicular to the joint axes
Classification • According to the form • According to the fiber direction • According to the function • According the number of joints • According to the position
Structure of the muscle Contractile (fleshy) part • Extrafusalmuscle fibers • Muscle fibers • Muscle bundles • Muscle
Connective tissue in the muscle 1.Endomysium. Thin layer around the muscle fiber. 2. Perimysium. Thicker layer around a bundle of muscle fibers (fascicle). 3. Epimysium. The outer connective tissue layer.
Muscle spindle • Proprioreception • Intrafusal muscle fibers • thin (30 mm) andshort (mm) • central portion (nuclear bag) - sensory endings • peripheral parts • motor endings of g-motoneurons
Intrafusal fibers – nuclear bagandnuclear chain. • Fusimotor fibers – motor nerve fibers. • Primary (Іа) andsecondary (ІІ)sensory nerve fibers. • Registers changes in the muscle length and speed. Sensation is modulated from CNS by fusimotor system: - static gamma system for changes in length - dynamic gamma system for changes in speed.
Muscle tendon Attachment of muscle • form – according to the muscle form • thickness – up to 20% muscle thickness • structure • collagen fibers • peritendineum– between and around the fibers • Golgi corpuscles– stretch receptors • blood vessels– less than in the muscle
Type I muscle fibers • Lowest contractile velocity • Lowest cross section surface • Highest aerobic capacity • Lowest anaerobic capacity • Slow, long-term contraction. • Long distance runners, swimmers
Type II muscle fibers Type II-b fibers have • Highest contractile velocity • Highest cross section surface • Lowest aerobic capacity • Highest anaerobic capacity • Quick, short-term contraction. • Sprint, weight-lifting, fitness Type II-a fibersare intermediate.
Auxiliary structures • Fasciae • proper – one muscle • group – synergic muscles • septae – separate neighbouring muscle groups
Synovial vaginae • Outer sheath • Inner sheath • Mesotenon
Synovial bursae • Beneath tendons and muscles, close to their insertions • Sesamoid bones • In tendons close to their insertions
Histological characteristics of muscle fibers 1.Cross striation. а. Dark and light bands. 1) А-bands. Dark–anisotropic 2) І-bands. Light -isotropic. б.1) Z disc in І band. 2) Н zone in А band; М линия, dark in Н.
Muscle biomechanics Internal biomechanics • Physiological transection – perpendicular to fibers • Anatomical transection – through the widest part of the muscle • Vector of muscle strength • Effectiveness of muscle strength -negatively proportional to the angle between the vector and the bone
Muscle biomechanics External biomechanics Movements in joints. • Synergists and antagonists Muscle strength. • Number and length of the fibers
External biomechanics Attachments • punctum mobile - insertion • punctum fixum - origin Levers of muscle contraction • Fulcrum • Point of load • Point of strength • I class lever – of equilibrium • II class lever • ІІА class – of strength • ІІВ class – of speed
Theory of sliding myofilaments Cycle of crossed bridges ATP required. • Crossed bridges • Myosin • On both sides of the myofilaments • Bidirectional on one side of the myofilament • А-bandsdo not change • І-bandsnarrow