Ascending pathways conduct sensory information upward toward the brain, typically through a relay chain of 3 successive neurons. The neurons in these sensory pathways are called the first-order, second-order and third-order neurons, respectively. Select the true statement regarding first-order neurons in somatosensory pathways.
A. First-order neurons usually ascend directly to the thalamus.
B. First-order neurons originate in the CNS.
C. First-order neurons descend with motor commands.
D. First-order neuron cell bodies reside in a ganglion.