Which statement regarding the relaxation phase of a muscle twitch is true?
A) The phase begins at stimulation and typically lasts about two milliseconds.
B) Muscle tension falls to resting levels.
C) The action potential sweeps across the sarcomere during this period.
D) Tension rises to a peak.
E) Cross-bridges are interacting with active sites on actin filaments throughout this period.

Question

Quizplus · Accepted Answer

During the relaxation phase, muscle tension falls to rest levels as calcium ions are actively pumped back into the sarcoplasmic reticulum and the cross-bridges detach from active sites on actin filaments. This phase occurs after the contraction phase, which is where tension rises to a peak. The relaxation phase typically lasts longer than two milliseconds.

Which Statement Regarding the Relaxation Phase of a Muscle Twitch