Test: MCAT Biology

Skeletal muscle fibers are not all contracted at once by the same action potential. Instead, muscle fibers are divided into clusters that can range from two to two thousand cells. All of these muscle fibers are innervated by the same neuron; the muscle fibers and the neuron that innervates them are collectively referred to as a motor unit.

9.

Which of the following statements is true concerning motor units?

Motor unit neurons only transmit one action potential during a contraction

Large motor units are innervated first in a muscle, followed by smaller units in order to have a smooth contraction

Finger muscles are typically composed of smaller motor units

The neuron releases epinephrine across the synaptic cleft in order to stimulate an action potential in the sarcolemma

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