Where does the first-order neuron carry the stimulus?

Where does the first-order neuron carry the stimulus?

• A. Into the spinal cord or brain
• B. Out to the periphery
• C. To the thalamus
• D. To the cerebellum

Answer: (A)

The essential idea is that the first-order sensory neuron carries the stimulus from the peripheral receptor into the central nervous system. Its cell body sits in a dorsal root ganglion, with a peripheral branch detecting the stimulus and a central branch that enters the spinal cord (or brainstem for cranial nerves) to synapse on the next neuron. So the signal is brought into the CNS, not sent back out to the periphery and not yet routed to the thalamus or cerebellum, which receive input after the signal has been relayed by higher-order neurons.

The essential idea is that the first-order sensory neuron carries the stimulus from the peripheral receptor into the central nervous system. Its cell body sits in a dorsal root ganglion, with a peripheral branch detecting the stimulus and a central branch that enters the spinal cord (or brainstem for cranial nerves) to synapse on the next neuron. So the signal is brought into the CNS, not sent back out to the periphery and not yet routed to the thalamus or cerebellum, which receive input after the signal has been relayed by higher-order neurons.