<prompt> The coupling agent between electrical excitation and contraction of a muscle is said to be:Dihydropyridine receptor DHPRRyanodine receptorCaTroponin C  <response>: Coupling: electrical excitation travels into muscle, releases calcium this calcium combines with troponin causes muscle contraction. Events tills the release of calcium is electrical after that is mechanical. T tubules contain DHPR L tubules contain RYR. 