Final answer:
The tract responsible for contralateral voluntary fine movement is the corticospinal tract, where signals originate from the primary motor cortex and control muscles on the opposite side of the body.
Step-by-step explanation:
The tract responsible for contralateral voluntary fine movement is the corticospinal tract. This major descending pathway originates from the primary motor cortex and transmits signals for the conscious or voluntary movements of skeletal muscles. Motor commands from the cortex travel down the axons of the Betz cells to activate upper motor neurons, which either synapse in the cranial motor nuclei or continue down into the ventral horn of the spinal cord. There, they synapse with lower motor neurons that control muscles on the opposite side of the body, hence contralateral.
The anterior corticospinal tract plays a role in coordinating postural muscles in broad movements of the body and is not entirely contralateral. Some axons project ipsilaterally to control synergistic muscles or inhibit antagonistic muscles. However, these axons are generally considered bilateral because they have an influence on both the ipsilateral and contralateral sides.
Figure 14.28 from the provided reference illustrates that the corticospinal tract is composed of two neurons: the upper motor neuron with a cell body in the primary motor cortex and the lower motor neuron in the ventral horn of the spinal cord, which subsequently projects to the peripheral skeletal muscle.