After a skeletal muscle has contracted, which process is most important for lowering Ca²⁺ levels in the cytoplasm? A) activity of the acetylcholine receptor B) activity of the Ca²⁺-ATPase pump C) closing of the Ca²⁺ release channels (ryanodine receptor) D) closing of the dihydropyridine receptor

Question

Quizplus · Accepted Answer

The Ca2+-ATPase pump is responsible for transporting Ca2+ from the cytoplasm back into the sarcoplasmic reticulum (SR) after muscle contraction. This reduces the levels of Ca2+ in the cytoplasm and allows for relaxation of the muscle fiber. The activity of the acetylcholine receptor, closing of the Ca2+ release channels (ryanodine receptor), and closing of the dihydropyridine receptor are all involved in the process of muscle contraction and not relaxation.

After a Skeletal Muscle Has Contracted, Which Process Is Most