{{B}}sEt 6BiologyCArDiAC musClE{{/B}}
whAt hAppEns whEn An ElECtriCAl impulsE gEnErAtED in onE pArt oF thE hEArt sprEADs to All thE CArDiAC musClE CEllsA．thE impulsE sprEADs to thE BonEs.
B．thE CArDiAC musClEs ExtEnD、
C、thE hEArt BEAts FAstEr.
D．thE wholE hEArt ContrACts.