Which statement is true about the principal sensory nucleus of CN V?

• A. It processes sensation from the face
• B. It controls muscles of mastication
• C. It is located in the medulla
• D. It receives olfactory input

Answer: (A)

The key idea here is what the principal (chief) sensory nucleus of CN V does and where it sits. This nucleus handles discriminative touch, vibration, and two-point discrimination from the face. It’s located in the pons as part of the trigeminal sensory complex. Primary sensory fibers from the face enter via the trigeminal ganglion and synapse in this nucleus; the second-order neurons then cross and ascend to the ventral posteromedial nucleus of the thalamus (the thalamic relay for face sensation) through the trigeminal lemniscus, ultimately reaching the somatosensory cortex. This makes it the correct description of its role. It’s not a motor nucleus, it isn’t in the medulla, and olfactory input is not carried through this pathway.