STRUCTURE OF SKELETAL MUSCLE

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For more information: • http://www.7activestudio.com • [email protected] • [email protected] • Contact: +91- 9700061777, • +91- 9100061777 • • 7 Active Technology Solutions Pvt.Ltd. is an educational 3D digital content provider for K-12. We also customise the content as per your requirement for companies platform providers colleges etc . 7 Active driving force The Joy of Happy Learning -- is what makes difference from other digital content providers. We consider Student needs, Lecturer needs and College needs in designing the 3D 2D Animated Video Lectures. We are carrying a huge 3D Digital Library ready to use. • • Types of Movement:Structure of Skeletal Muscle: Each skeletal muscle is made of a number of muscle bundles or fascicles held together by a common collagenous connective tissue layer called fascia. Each muscle bundle consists of a number of muscle fibres. Each muscle fibre is lined by the plasma membrane called sarcolemma enclosing the sarcoplasm. Muscle fibre is a syncitium as the sarcoplasm contains many nuclei and mitochondria. The endoplasmic reticulum i.e. sarcoplasmic reticulum of the muscle fibre is the store house of calcium ions.A characteristic feature of the muscle fibre is the presence of large number of parallely arranged filaments in the sarcoplasm called myofilaments or myofibrils. The myofibrils are stacked in compartments called sarcomeres. Each myofibril has alternate dark and light bands on it. The study of myofibril revealed that the striated appearance is due to the distribution pattern of two proteins -- Actin and Myosin. Both are contractile proteins. The light band contains actin and is called 'i' band or isotropic band, whereas the dark band is called 'A' band or Anisotropic band and it contains myosin. Both the proteins are arranged as rod like structures, parallel to each other and also, to the longitudinal axis of the myofibrils. Actin filaments are thinner as compared to the myosin filaments, hence are commonly called thin and thick filaments. In the centre of each 'i' band is an elastic fibre called 'Z' line which bisects it. The thin filaments are firmly attached to the Z line. The thick filaments in the A -- band are also held together in the middle of this band by a thin fibrous membrane called M - line. The A and i bands are arranged alternately throughout the length of the myofibrils. The portion of the myofibril between 2 successive 'Z' lines is considered as functional unit of contraction and is called a sacromere. In the resting state, the edges of thin filaments on either side of the thick filaments partially overlap the free ends of the thick filaments leaving the central part of the thick filament. The central part of thick filament, not overlapped by thin filaments is called the 'H' zone.

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