Discuss the mechanism of action of skeletal muscles

Discuss the mechanism of action of skeletal muscles, focusing on the sliding filament theory and the role of actin, myosin, calcium ions, and ATP in muscle contraction, as well as the neuromuscular junction and motor unit recruitment.Elaborate on the structure and function of the respiratory system, encompassing the anatomy of the lungs, trachea, bronchi, and alveoli, as well as the process of ventilation, gas exchange, and the regulation of breathing by the respiratory centers in the brainstem.