What happens after the action potential travels down the T tubule during excitation-contraction coupling?

Following the arrival of an action potential in the T tubule, a key event involves the interaction of voltage-gated proteins within the T tubule membrane. These proteins undergo a conformational change in response to the changes in voltage associated with the action potential. This change is crucial because it triggers the opening of nearby calcium ion channels located in the terminal cisternae of the sarcoplasmic reticulum.

The release of calcium ions is vital for the process of excitation-contraction coupling, as the increase in intracellular calcium concentration enables the binding of calcium to troponin, causing a series of events that ultimately lead to muscle contraction. Therefore, the correct response highlights the importance of the structural changes in the tubule proteins as a preliminary step that facilitates the release of calcium ions necessary for muscle contraction.