The ability of a muscle to contract and relax is dependent on the flow of what substance out of and into its storage site in the muscle cell?
A) phosphorus
B) calcium
C) iron
D) chloride

Question

Quizplus · Accepted Answer

The substance needed for muscle contraction and relaxation is calcium. Calcium is stored in the sarcoplasmic reticulum within muscle cells and is released during muscle contraction to activate the muscle fibers. When the calcium is pumped back into the sarcoplasmic reticulum, the muscle relaxes.

The Ability of a Muscle to Contract and Relax Is