Title: 5. Molecular mechanism of skeletal muscle contraction. Structure of skeletal muscle. The regulatory role of calcium ion – greek.doctor
Headings: 5. Molecular mechanism of skeletal muscle contraction. Structure of skeletal muscle. The regulatory role of calcium ion
5. Molecular mechanism of skeletal muscle contraction. Structure of skeletal muscle. The regulatory role of calcium ion
Table of Contents
Learning objectives
General principles of muscles
Excitation-contraction coupling
General structure of muscle cells
Structure and contraction of skeletal muscle
Structure of skeletal muscle
Mechanism of excitation
Mechanism of contraction
Termination of contraction

Content: During contraction, both the thin and thick filaments themselves remain the same length. However, they will slide on each other, which brings the Z-discs closer together and decreases the size of the I-band, as well as the length of the sarcomere. The sarcolemma of skeletal and cardiac muscle has deep invaginations which penetrate into the muscle fibres. These are called T-tubules, short for transverse tubules. The T-tubules open into the sarcoplasmic reticulum at the so-called terminal cisternae. The action potential which causes muscle contraction propagates along the sarcolemma and the T-tubules. The network of T-tubules allows the action potential to propagate through the muscle cell much faster. The T-tubules contain a protein which is important for excitation-contraction coupling, called the dihydropyridine receptor (DHPR). The nearby sarcoplasmic reticulum contains a different protein called the ryanodine receptor, which is a calcium channel. The DHPR is voltage-sensitive, meaning that it is activated when depolarization occurs.