Identify the incorrect statement about a single motor unit.
- fine motor skills depend on the development of small motor units.
- the smaller the number of muscle fibers, the more precise the movement.
- muscle fibers of one motor unit intermingle with the fibers of another motor unit.
- some motor units include as many as 2000 muscle fibers.
- the more neurons involved, the more powerful the contraction.

The incorrect statement is: The more neurons involved, the more powerful the contraction.

The motor neuron cell is connected to muscle cell via synaptic cleft, where neurotransmitter is released. A motor neuron and that skeletal muscle cell  form a motor unit. The muscle side of this synapse is called motor end plate. Released neurotransmitter is acetylcholine and it binds to its receptor (ACh receptor) on the motor end plate. As it binds, ion channels open, and Na+ gets into the muscle cell. This event reduces the voltage difference between the inside and outside of the cell and causes depolarization which creates a wave through the entire muscle cell (its membrane-sarcolema). As a consequence, Ca2+ is released from the sarcoplasmic reticulum which will cause the contraction of the muscle cell.

Muscles that have more motor units are capable to control force output more finely. The number of motor units determinate the force of a muscle contraction.