Question

even though a particular muscle fiber may experience a partial tetanic contraction, a muscle as a whole usually experiences smooth contractions. why? as more motor units contract, extracellular calcium levels decrease. different sets of motor units are stimulated at different times. during contraction of a muscle, most muscle fibers in a muscle are experiencing individual twitches. need help? review these concept resources. rate your confidence to submit your answer. high medium low reading 2025 mcgraw hill. all rights reserved. privacy center terms of use

Explanation:

Muscles are made up of multiple motor - units. Smooth muscle contractions occur because different sets of motor units are activated at different times, which allows for a continuous and smooth overall contraction even if individual fibers may have partial contractions. When more motor units contract, extracellular calcium levels do not decrease in a way that explains smooth contractions. Also, during smooth muscle contractions, it's not that most muscle fibers are experiencing individual twitches as this would lead to jerky, not smooth, contractions.

Answer:

B. Different sets of motor units are stimulated at different times.