A patient with a facial nerve paralysis suffers from inability to dampen loud noises due to denervation of which muscle?
**Core Concept**
The facial nerve (cranial nerve VII) controls the muscles of facial expression, including the stapedius muscle in the middle ear. The stapedius muscle plays a crucial role in protecting the ear from loud noises by dampening sound waves. Facial nerve paralysis can lead to denervation of this muscle, resulting in an inability to dampen loud noises.
**Why the Correct Answer is Right**
The stapedius muscle is innervated by the facial nerve, specifically the nerve to the stapedius, which is a branch of the facial nerve. When the facial nerve is paralyzed, the stapedius muscle fails to contract, leading to an inability to dampen loud noises. This is due to the loss of motor control over the stapedius muscle, which normally contracts in response to loud sounds to reduce the transmission of sound waves to the inner ear.
**Why Each Wrong Option is Incorrect**
* **Option A:** The digastric muscle, which is innervated by the mandibular division of the trigeminal nerve (cranial nerve V), is not involved in dampening loud noises.
* **Option B:** The tensor tympani muscle, which is innervated by the mandibular division of the trigeminal nerve (cranial nerve V), also helps to dampen loud noises, but it is not the muscle primarily affected by facial nerve paralysis.
* **Option D:** The muscles of mastication, which are innervated by the trigeminal nerve (cranial nerve V), are not directly involved in dampening loud noises.
**Clinical Pearl / High-Yield Fact**
Facial nerve paralysis can lead to an inability to dampen loud noises due to denervation of the stapedius muscle, highlighting the importance of the facial nerve in protecting the ear from loud sounds.
**Correct Answer:** C. Stapedius