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 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. 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.