Sports Physiology Postgraduate Examination Knowledge: Muscle Contraction Coupling Mechanism

Muscle contraction coupling mechanism

Generally, the intermediary process between the excitation process characterized by the electrical changes of muscle cell membrane and the contraction process based on the smooth muscle behavior is called excitation contraction coupling. It includes the following three main steps:

(1) Excitement (action potential) is transmitted into muscle cells through the transverse tubular system

The transverse tubule is the continuation of the muscle cell membrane, and the action potential can be transmitted to the transverse tubule along the muscle cell membrane, and go deep into the triad structure.

(2) Information transmission at the triple pipe structure

The action potential on the transverse tubular membrane can cause a large number of Ca2+channels on the terminal cistern membrane and sarcoplasmic reticulum adjacent to it to open, and Ca2+flows into the sarcoplasm along the concentration gradient from the sarcoplasmic reticulum. After the concentration of Ca2+in the sarcoplasm increases, when Ca2+combines with troponin subunit C, a series of changes in the configuration of albumin will occur, eventually leading to the slippage of myofilaments.

(3) Sarcoplasmic reticulum recycling Ca2+

The Ca2+- Mg2+dependent ATPase (calcium pump) exists on the sarcoplasmic reticulum. When the concentration of Ca2+in the muscle plasma increases, the calcium pump transports Ca2+in the muscle plasma against the concentration gradient to the sarcoplasmic reticulum for storage, thus keeping the concentration of sarcoplasmic Ca2+at a low level. As the concentration of Ca2+in the muscle plasma decreases, Ca2+is separated from the troponin subunit C, which eventually causes muscle relaxation.