Coupling, depolarization conduction and Ca2+ release processes occur in the excitation and contraction of skeletal and cardiac (E-C) muscles. Although the proteins involved are similar, they differ in structure and regulation. Dihydropyridine receptors (DHPR) are encoded by different genes, and ryanodine receptors (RyRs) are different isoforms. In addition, DHPR touches with RyR1 (main isoform of RyR in skeletal muscle) to regulate the release of Ca2+ in skeletal muscle, while the L-type calcium channel (DHPR on cardiac myocytes) and RyR2 (main RyR isoform in heart muscle) in the heart muscle are not physically coupled, but face each other through compound coupling.  It is possible to distinguish two main types of muscle fibers in pathological and physiological studies: muscles are made up of muscle tissue and are responsible for functions such as maintaining posture, locomotion and controlling various circulatory systems. These include the heartbeat and the movement of food through the digestive system. Muscles are closely related to the skeletal system to facilitate movement. The voluntary and involuntary functions of the muscles are controlled by the nervous system. Myocytes: Skeletal muscle cell: A skeletal muscle cell is surrounded by a plasma membrane called a sarcolemma, along with a cytoplasm called a sarcoplasm. A muscle fiber consists of many myofibrils, which are packed in ordered units. Explaining the excitation-contraction coupling process and the role of neurotransmitters In 1780, Luigi Galvani discovered that the leg muscles of dead frogs contracted when hit by an electric spark.
 This was one of the first forays into the study of bioelectricity, a field that still studies electrical patterns and signals in tissues such as nerves and muscles. Muscles: The skeletal muscles of the muscles are closely related to the skeletal system and work to maintain posture and control voluntary movement. Heart muscle tissue is located only in the heart, where heart contractions pump blood through the body and maintain blood pressure. The end of the crossbridge cycle (and the exit of the muscle in the latch state) occurs when the light-chain phosphatase of myosin removes phosphate groups from myosin heads. Phosphorylation of 20 kDa myosin light chains is well correlated with the speed of shortening of smooth muscles. Meanwhile, there is a rapid eruption of energy consumption, measured by oxygen consumption. A few minutes after their appearance, calcium levels drop significantly, phosphorylation of 20 kDa myosin light chains decreases, and energy consumption decreases; However, the strength of the tonic smooth muscles is preserved. During muscle contraction, rapidly changing transverse bridges form between activated actin and phosphorylated myosin, creating strength. He hypothesizes that force maintenance results from dephosphorylated “locking bridges” that circulate slowly and maintain force.
A number of kinases such as rhokinase, DAPK3 and protein kinase C are thought to participate in the prolonged phase of contraction, and the flow of Ca2+ may be significant. Huxley, H. E. & Hanson, J. Changes in the transverse bands of muscles during contraction and stretching and their structural interpretation. Nature 173, 973–976 (1954) doi:10.1038/173973a0. Figure 3. Organization of the SR and T tubules in skeletal muscle. Each myofiber is formed by several myofibrils (brown and red) surrounded by SR (light blue). The SR is interrupted by T-shaped tubules (light green), which are intussusceptions of the sarcolemma, and therefore its light communicates with the extracellular space. The process of muscle contraction requires ATP, which is necessary for the activity of various proteins such as myosins, serca and the Na+/K+ pump, with the last two proteins accounting for 40% of the total ATP consumption in the skeletal muscle cell.5 ATP is produced by mitochondrial glycolysis and respiration.
In turn, mitochondria produce ATP using O2 and produce ROS such as superoxide, hydrogen peroxide and hydroxyl residues. Especially during muscle contraction, there is a physiological production of ROS. As the intensity of muscle work increases, ros production also increases, resulting in an imbalance in the prooxidative/antioxidant balance. Therefore, ROS contribute to the establishment of fatigue by oxidizing various basic proteins involved in muscle contraction. The known targets of oxidation are not only the Na+/K+ pump, myosins and other myofilamentary proteins such as DHPR and RyR1, but also sarcolematal lipids, which leads to an increase in leakage of SR Ca2+ and a decrease in myofibrillary sensitivity Ca2+.6,7 Overall, ros contributes to the development of muscle fatigue by altering sarcolemic excitability, by modifying the absorption and release of Ca2+. Change in myofilament affinity for Ca2+ and impaired mechanical function of myosin.4,6,7 Finally, ROS has also been shown to alter muscle contraction by directly inhibiting motor neurons.4 The number of transverse bridges formed between actin and myosin determines the amount of tension a muscle fiber can generate. Transverse bridges can only form where thick, thin filaments overlap, allowing myosin to bind to actin. As more transverse bridges form, more myosin will pull on the actin and create more tension. Skeletal muscle consists of striated subunits called sarcomeres, which consist of the myofilaments actin and myosin. Imagine standing between two large shelves full of books.
These large shelves are spaced several meters apart and positioned on rails so that they can be easily moved. You have the task of bringing the two shelves together, but you are limited to using only your arms and two ropes. If you stand in the middle between the shelves, pull on the two ropes – one per arm – that are securely attached to each shelf. .