Which are the main functions of the hypoglossal nerve?

RRB Nsg. Superintendent-20 July 2019 (Shift-2)

Applied Physiology

Easy

Appeared in: RRB Nsg. Superintendent-20 July 2019 (Shift-2)

Explanation

The hypoglossal nerve (Cranial Nerve XII) is a motor nerve responsible for innervating all the intrinsic and extrinsic muscles of the tongue, with the exception of the palatoglossus muscle.
These tongue muscles are crucial for complex movements required for manipulating food to form a bolus and initiating the process of swallowing.
The fine motor control of the tongue, managed by the hypoglossal nerve, is also essential for the precise articulation of sounds required for clear speech.

Option A: This option is incorrect. Vision is the primary function of the Optic nerve (CN II), and general sensation from the face is mediated by the Trigeminal nerve (CN V).
Option B: This option is incorrect. Hearing is the function of the Vestibulocochlear nerve (CN VIII), and facial sensation is from the Trigeminal nerve (CN V).
Option C: This option is incorrect. Hearing is the function of the Vestibulocochlear nerve (CN VIII), and the sense of smell is the function of the Olfactory nerve (CN I).

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Function of the Hypoglossal Nerve (Cranial Nerve XII) as background academic context rather than a clinical decision trigger.
Assessing the hypoglossal nerve is a key part of a neurological examination. A nurse may ask the patient to stick out their tongue and move it side-to-side to check for deviation, weakness, or atrophy.
Damage to the hypoglossal nerve can lead to dysarthria (difficulty speaking) and dysphagia (difficulty swallowing), increasing the risk of aspiration.
What if? If a patient's tongue deviates to the left side when they stick it out, it indicates a lesion or damage to the left hypoglossal nerve. The tongue points toward the side of the lesion due to the unopposed action of the healthy side's muscles.

How to Approach the Question

First, identify the core subject of the question: the function of the hypoglossal nerve.
Recall the 12 cranial nerves and their primary functions (motor, sensory, or both). The hypoglossal nerve is Cranial Nerve XII.
The name itself provides a clue: 'hypo' means under, and 'glossal' relates to the tongue. This points to its function involving the tongue.
Evaluate the options based on this knowledge. The tongue is critical for manipulating food (swallowing) and forming words (speech).
Eliminate options containing functions of other well-known cranial nerves: Vision (Optic - CN II), Hearing (Vestibulocochlear - CN VIII), Smell (Olfactory - CN I), and facial Sensation (Trigeminal - CN V).
This process of elimination confirms that swallowing and speech are the functions associated with the hypoglossal nerve's control over the tongue.

Concept Tested & Keywords

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E6 Anatomy Grays 43e Vol 2 Part 1 pp. 85-87, 41-43

E6 Anatomy Applied Ashalatha 4e p. 432-434