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: The activated DHPR then opens the ryanodine receptor. This image shows the T-tubules as invaginations of the sarcolemma, as well as the terminal cisternae through which the T-tubules communicate with the sarcoplasmic reticulum. From https://en.wikipedia.org/wiki/T-tubule
Mechanism of excitation
When the alpha motoneuron creates an action potential, it will reach the neuromuscular junction. The neuromuscular junction will form a new action potential on the motor endplate. This action potential will spread along the sarcolemma of the skeletal muscle cell and into the T-tubules. The action potential will activate the dihydropyridine receptors in the T-tubules, which will open the ryanodine receptors, allowing Ca 2+ to flow out from the sarcoplasmic reticulum and into the sarcoplasm. Mechanism of contraction
During rest, when there is no contraction, the protein tropomyosin prevents actin and myosin from interacting with each other, thereby preventing contraction. Before contraction, the myosin heads hydrolyse one ATP into ADP and inorganic phosphate. This hydrolysis puts the head in a high-energy state: we say that the head is now “cocked”.