Biological Systems MCAT Practice Exam

Which muscle contraction type involves rapid consecutive contractions that prevent calcium sequestration?

1. Muscle twitch

2. Fatigue

3. Tetanus

4. Isometric contraction

The correct answer is: Tetanus

The type of muscle contraction characterized by rapid and consecutive contractions that result in a sustained muscle contraction and prevent calcium sequestration is tetanus. During tetanus, the frequency of stimulation is high enough that the muscle fibers do not have time to relax between stimuli, leading to a continual presence of calcium ions in the cytoplasm. This sustained elevation in calcium levels keeps the actin and myosin filaments engaged, producing a strong and continuous contraction. In contrast, a muscle twitch is a single contraction response to a single stimulus, and it allows for calcium to be re-sequestered before another contraction can occur. Fatigue, while it can occur alongside tetanus, specifically refers to the reduced ability of muscles to perform work after prolonged activity, not the nature of the contraction itself. Isometric contraction refers to muscle contractions where the muscle remains at constant length even while tension is generated, which differs significantly from the rapid contractions seen in tetanus. Thus, the phenomenon of tetanus best describes the scenario presented in the question.