The factor(s) that determine the duration of a twitch in various types of fibers is the speed of the
A) removal of Ca2+ ions from the sarcoplasm only.
B) hydrolysis of ATP only.
C) movement of Na+ across their membranes only.
D) removal of Ca2+ ions from the sarcoplasm and hydrolysis of ATP.
E) removal of Ca2+ ions from the sarcoplasm and hydrolysis of ATP and movement of Na+ across their membranes.
Answer: : A