University:
Western Sydney University
Course:
MEDI 2003 | Clinical Sciences 2
Academic year:

2024
Views:

110

Pages:

3
Author:

Mariam A. A.

Sarcomere structure • • • • • • Each myophily is composed of repeating sections called sarcomeres, which appear under the microscope as dark and light bands. Each sarcomere is composed of long thick and thin filaments that slide past each other when a muscle contracts or relaxes. A sarcomere is defined as the segment between two neighbouring Z-lines Thick filaments are composed of the protein myosin 10–12 nm diameter Thin filaments are composed of the protein actin 5–6 nm diameter Important structures: 3 bands; 2 lines • Areas of overlap are responsible for the light and dark striations typical of skeletal muscle • Thin and Thick Filaments - Each thin filament consists of a twisted strand of several interacting proteins 5–6 nm in diameter and 1 μm in length. • • • • • Sarcomeres contract according to the sliding filament hypothesis , which explains how muscle contracts through cross bridges between the actin and myosin filaments According to the sliding filament theory, the actin (thin) filaments of muscle fibers slide past the myosin (thick) filaments during muscle contraction, while the two groups of filaments remain at relatively constant length Following calcium release from the SR, calcium binds to the troponin. Troponins change its shape, alters the position of the tropomyosin strand and expose the active sites on the actin molecules Once the myosin and actin filaments are attached, the myosin filaments push the actin filaments, using ATP hydrolysis and a power stroke