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MCAT Biology Question — Synapses

In order to send pain signals to the brain, a nerve in the spinal cord would have to synapse with an:


A. afferent dorsal motor neuron

B. efferent ventral sensory neuron

C. afferent dorsal sensory neuron

D. efferent ventral motor neuron

Click for Explanation

Sensory neurons are afferent (from periphery to central) and enter dorsally within the spinal cord. Motor neurons are efferent (from central to periphery) and leave the spinal cord ventrally. An interneuron carrying pain sensation to the brain would synapse with an afferent, dorsal sensory neuron.

A. afferent dorsal motor neuron, incorrect, Motor neurons are efferent and ventral.

B. efferent ventral sensory neuron, incorrect, Sensory neurons are afferent and dorsal.

C. afferent dorsal sensory neuron,  correct.

D. efferent ventral motor neuron, incorrect, Motor neurons are efferent and ventral, but an interneuron would synapse with the afferent sensory nerve in order to carry the incoming signal to the brain.

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