Which cranial nerve is responsible for gag reflex?

Appeared in: AIIMS BHOPAL NO- 2018( Shift-2nd)

Explanation

The gag reflex is a complex reflex arc mediated by two distinct cranial nerves.
The Glossopharyngeal nerve (CN IX) serves as the sensory (afferent) limb, detecting the stimulus at the back of the throat.
The Vagus nerve (CN X) serves as the motor (efferent) limb, triggering the contraction of the pharyngeal muscles in response.
Therefore, both CN IX and CN X are essential for a normal gag reflex.

Option A: This pair of nerves is incorrect. While both are involved in a facial reflex, it is the corneal (blink) reflex, not the gag reflex.
Option C: This pair of nerves is incorrect. Their primary function relates to the control of eye movements.
Option D: This pair of nerves is incorrect. They control muscles of the neck/shoulders and the tongue, respectively, not the pharynx for the gag reflex.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Cranial nerve functions and reflexes as background academic context rather than a clinical decision trigger.
Assessing the gag reflex is a critical nursing intervention for patients with a decreased level of consciousness, after a stroke (CVA), or before initiating oral feeding to evaluate the risk of aspiration.
An absent or diminished gag reflex indicates a high risk for aspiration, and the nurse must implement aspiration precautions, such as keeping the patient NPO (nothing by mouth) and notifying the physician.
What if? If, upon saying 'Ah,' the patient's uvula deviates to the left, it suggests a lesion of the right Vagus nerve (CN X). The palate muscles on the strong (left) side pull the uvula towards them.

How to Approach the Question

First, identify the key concept in the question stem: 'gag reflex'.
This is a factual recall question that requires knowledge of cranial nerve functions.
Recall the specific reflex arc for the gag reflex. Remember that reflexes have a sensory (afferent) and a motor (efferent) component.
Associate the Glossopharyngeal nerve (CN IX) with sensation from the pharynx and the Vagus nerve (CN X) with motor control of the pharynx.
Evaluate the options. Eliminate pairs of nerves whose primary functions are unrelated to the pharynx, such as eye movement (CN III, IV), facial sensation/expression (CN V, VII), or neck/tongue movement (CN XI, XII).

Concept Tested & Keywords

QBN2kUewFupM24ReHpdvZu

E6 Nelson Textbook of Pediatrics(2024) — Volume 2 p. 1360-1362

E6 Medicine Macleod Clinical Examination 15e p. 154-156

Practise the full AIIMS BHOPAL NO- 2018( Shift-2nd)

Attempt every question from this paper in a timed mock, then review the full solution for each one.