Final answer:
The two tracts of cortical motor commands are the corticobulbar tract and the corticospinal tract, which handle voluntary movements and muscle strength through the UMN and LMN.
Step-by-step explanation:
The two tracts of cortical motor commands responsible for the conscious or voluntary movements of skeletal muscles are the corticobulbar tract and the corticospinal tract.
The corticobulbar tract sends motor commands from the cortex to motor nuclei on the same side of the nervous system (ipsilateral), whereas the corticospinal tract's axons, after originating in the motor cortex, cross the midline of the brain stem or spinal cord and synapse on the opposite side of the body (largely contralateral).
This crossing over occurs at the pyramidal decussation located at the junction between the medulla and the spinal cord.
Muscle strength and voluntary movement in these systems rely on two neurons: the upper motor neuron (UMN) and the lower motor neuron (LMN).
The UMN originates in the primary motor cortex and synapses on the LMN in the ventral horn of the spinal cord. The LMN extends from the spinal cord to the muscles, enabling contraction and facilitating voluntary movements.