Which of the following correctly outlines the first step in excitation-contraction coupling?

The first step in excitation-contraction coupling involves the generation of an action potential at the sarcolemma, which is the muscle cell membrane. This action potential is crucial because it signals the muscle fiber to initiate the contraction process.

When an action potential is generated, it travels along the sarcolemma and down the T-tubules, leading to a series of events that ultimately results in muscle contraction. This electrical impulse allows for the rapid communication necessary to coordinate muscle activity, setting the stage for subsequent steps in the contraction process, such as calcium release from the sarcoplasmic reticulum and interaction between actin and myosin.

Other processes, such as calcium binding to troponin or the formation of cross bridges in muscle fibers, occur after this initial action potential. Therefore, the generation of the action potential is indeed the foundational first step in the chain of events that leads to muscle contraction.