Stapedial reflex is mediated by-
**Core Concept**
The stapedial reflex is a vital auditory reflex that protects the ear from loud sounds. It involves the contraction of the stapedius muscle, which is innervated by the facial nerve (cranial nerve VII). This reflex plays a crucial role in maintaining hearing and preventing damage to the inner ear.
**Why the Correct Answer is Right**
The stapedial reflex is mediated by the stapedius muscle, which receives its motor innervation from the facial nerve (cranial nerve VII). The reflex arc involves the following components:
* The cochlear nerve (cranial nerve VIII) detects loud sounds and transmits this information to the brain.
* The brain sends a signal to the facial nerve (cranial nerve VII), which then stimulates the stapedius muscle.
* The stapedius muscle contracts, reducing the transmission of sound waves to the inner ear and protecting it from damage.
**Why Each Wrong Option is Incorrect**
**Option A:** is incorrect because the stapedial reflex is not mediated by the trigeminal nerve (cranial nerve V). The trigeminal nerve is responsible for facial sensation and motor functions, but it is not involved in the stapedial reflex.
**Option B:** is incorrect because the glossopharyngeal nerve (cranial nerve IX) is responsible for swallowing and taste, but it is not involved in the stapedial reflex.
**Option C:** is incorrect because the vagus nerve (cranial nerve X) is responsible for various functions, including swallowing and heart rate regulation, but it is not involved in the stapedial reflex.
**Clinical Pearl / High-Yield Fact**
The stapedial reflex is an important indicator of the integrity of the facial nerve and the stapedius muscle. Abnormalities in this reflex can indicate conditions such as Bell's palsy or otosclerosis.
**Correct Answer:** C. The stapedial reflex is indeed mediated by the facial nerve (cranial nerve VII).