What is the correct order of events in the pathway leading up to the release of calcium from the sarcoplasmic reticulum of a skeletal muscle cell?
A) Plasma membrane of muscle cell; T tubules; ryanodine receptor; dihydropyridine (DHP) receptor
B) T tubules; plasma membrane of muscle cell; DHP receptor; ryanodine receptor
C) Plasma membrane of muscle cell; T tubules; DHP receptor; ryanodine receptor
D) DHP receptor; plasma membrane of muscle cell; T tubules; ryanodine receptor
E) Ryanodine receptor; plasma membrane of muscle cell; T tubules; DHP receptor

Question

Quizplus · Accepted Answer

The correct order of events leading up to the release of calcium from the sarcoplasmic reticulum of a skeletal muscle cell is as follows: The action potential arrives at the plasma membrane of the muscle cell, which then spreads deep into the T-tubules. The DHP receptor in the T-tubules senses the depolarization and undergoes a conformational change, which activates the nearby ryanodine receptor in the sarcoplasmic reticulum. The activated ryanodine receptor allows calcium ions to flow out of the sarcoplasmic reticulum and into the cytosol. Therefore, the correct order of events is plasma membrane of muscle cell; T tubules; DHP receptor; ryanodine receptor. Choice C is the only option that represents this order of events.

What Is the Correct Order of Events in the Pathway