What causes muscle relaxation?

Question

Quizplus · Accepted Answer

Muscle relaxation is caused by the return of calcium ions to the lateral sacs of the sarcoplasmic reticulum (SR). When calcium ions are released from the SR into the muscle fibers during muscle contraction, they bind to troponin, which causes a conformational change in tropomyosin, revealing binding sites on the actin filament for the myosin heads. When calcium ions are actively transported back into the SR, troponin and tropomyosin return to their original positions, which blocks the myosin heads from binding to actin, resulting in muscle relaxation.

What Causes Muscle Relaxation