PHYS30005 Lecture Notes - Lecture 5: Protein Isoform, Lipid-Anchored Protein, Cell Adhesion
13 Aug 2020
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Online lecture 5 - key structural proteins of skeletal muscle. Muscle belly - composed of muscle fibers composed of myofibrils. Skeletal muscle fibers are composed of bundles of myofibrils which are segmented into functional units termed sarcomeres . Run b/w z-discs along the length of the myofibril. Rib-like structures across the surface of the sarcolemma. Specialized sites of transmembrane complexes, occurring over the entire sarcolemma, where the transmission of force is concentrated. Stabilizes sarcolemma during contraction esp. during forced lengthening. Mechanical links b/w the sarcomeres within muscle fiber and laminin in the ecm (binds laminin to the external machinery) In the image: each green line is the costamere. Sit at the level of the z-line. Function link the extracellular matrix, through the cell membrane (sarcolemma), to the functional myosin/actin units of the muscle. B: during contraction it holds the ecm to the z-line, so when contraction occurs it comes through the entire unit.
