Question

a muscle or group of muscles opposing an action is called the: prime mover antagonist synergist agonist question 53 if the nerve impulse does not reach the required magnitude, only some of the muscle fibers will contract. true false question 54 whether or not a motor unit activates upon the arrival of an impulse depends on its

Explanation:

1. In muscle - action terminology, an antagonist is a muscle or group of muscles that opposes the action of another muscle (the agonist). A prime mover is the main muscle responsible for an action, a synergist helps the prime mover, and an agonist is the muscle that causes a particular action.
2. For muscle - fiber contraction, the all - or - none law states that a muscle fiber will either contract fully when the nerve impulse reaches the threshold or not contract at all. So, if the nerve impulse does not reach the required magnitude, no muscle fibers will contract, not just some.

Answer:

1. B. antagonist
2. False