Nah
wave of depol traverses the t-tubules, allowing it to spread to the SR, where voltage-gated Ca2+ channels reside to open & allow Ca2+ efflux into the cytosol (more specifically, first goes through L-type Ca2+ channels on t-tubules, then ryanodine receptors on the SR, activated via mechanical linkages to the L-types and via Ca2+ itself. Then that mediates the main cytosolic Ca2+ flux for muscle contraction)

if talking about muscle, make sure to mention these ryanodine receptors: http://en.wikipedia.org/wiki/RYR1 people love hearing about that shit if possible

also, depending on the depth of your course, look up malignant hyperthermia due to RYR mutation. Treatment = dantrolene

I'm using some substances that act through voltage gated Ca++ channels....it's called....XANNIES AND KLONNIES