Is only active transport used to move calcium across cell membranes or is simple or facilitated diffusion used as well?

what mechanism do you think a voltage-gated Ca2+ channel would be, for instance?

small ions diffuse fairly easily through membranes, thus there is somewhat constant leaking (not a great degree relatively speaking). facilitated transport such as ion channels are used to induce quick changes in ion polarity, and active transport across membranes (reliant usually on ATP hydrolysis) maintains normal homeostatic concentration gradients.

Facilitated . So I guess it's both active and facilitated . Thanks you two

you could probably say passive too but yes

Oh okay. Thanks. Got my exam on Thursday and just trying to iron out the little kinks I couldn't remember

theres a sarcoplasmic Ca ATPase that regulates cytoplasmic calcium for muscle contraction. there are voltage gated Ca channels that balla mentioned involved in the neuromuscular junction (ach vesicle exocytosis) etc etc

The calcium during the muscle contraction is released into the t tubules from the sr?

Yes, if I remember accordingly there is a more specific name not t tubules, but people often refer it to t tubules.

Transverse tubules