MCQ – 100774

Correct Answer � A Explanation

Olfaction, or the sense of smell, is primarily mediated by the olfactory nerve (Cranial Nerve I). However, other cranial nerves can be indirectly involved in the perception of odors through somatosensory, chemical irritation, or reflex responses (e.g., gag or cough).

A. Hypoglossal nerve (CN XII)

• Function: Purely motor to the muscles of the tongue.

• Relation to olfaction: None. It does not carry any sensory or olfactory fibers.

B. Trigeminal nerve (CN V)

• Function: Sensory to the face and anterior nasal cavity.

• Relation to olfaction: While not directly involved in smell perception, the ophthalmic (V1) and maxillary (V2) divisions of the trigeminal nerve detect chemical irritants (like ammonia or menthol) that stimulate the nasal mucosa.

C. Glossopharyngeal nerve (CN IX)

• Function: Sensory to posterior one-third of the tongue and upper pharynx, also involved in taste.

• Relation to olfaction: Indirect. It may participate in reflex responses (like gag) triggered by strong smells.

D. Vagus nerve (CN X)

• Function: Sensory and motor to various structures including pharynx and larynx; also part of parasympathetic innervation.

• Relation to olfaction: Also indirectly involved. Strong odors (e.g., putrid smells) can trigger vomiting or coughing reflexes via vagus nerve stimulation.