The coupling agent between electrical excitation and contraction of a muscle is said to be:
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.
Dihydropyridine receptor (DHPR)
Ryanodine receptor
Ca++
Troponin C
Muscle