The voluntary action of muscle is controlled by signals from the nervous system called _____.

The correct completion of the statement regarding the voluntary action of muscle being controlled by signals from the nervous system is action potentials. Action potentials are quick, transient changes in the membrane potential of a neuron or muscle cell that play a crucial role in transmitting signals throughout the nervous system. When a motor neuron sends an action potential to a muscle fiber, it initiates a series of reactions that ultimately lead to muscle contraction. This process begins at the neuromuscular junction, where the action potential causes the release of neurotransmitters, leading to excitation of the muscle.

The other options do not specifically capture the precise physiological event that occurs with muscle activation. While motor signals may be a term used in a broader context, they do not represent the specific electrical phenomenon that drives the contraction of muscles. Voluntary impulses also lacks the specificity and technical definition that action potentials provide, while dynamic reflexes refer to involuntary responses and do not pertain to the voluntary control required for muscle movement. Thus, action potentials are the fundamental signals required for the voluntary action of muscle initiated by the nervous system.