CN VII innervates which middle ear muscle used to dampen sound?

CN VII innervates which middle ear muscle used to dampen sound?

• A. Tensor Tympani
• B. Stapedius
• C. Malleus
• D. Incus

Answer: (B)

The key idea is that the facial nerve (CN VII) supplies the stapedius muscle in the middle ear. When the stapedius contracts, it pulls on the stapes to stiffen the ossicular chain, which dampens the transmission of loud sounds to the inner ear and helps protect hearing. The tensor tympani, which also helps dampen sound by tenseing the tympanic membrane, is innervated by the mandibular division of CN V, not CN VII. The malleus and incus are bones (ossicles) rather than muscles, so they aren’t innervated to produce a dampening action.

The key idea is that the facial nerve (CN VII) supplies the stapedius muscle in the middle ear. When the stapedius contracts, it pulls on the stapes to stiffen the ossicular chain, which dampens the transmission of loud sounds to the inner ear and helps protect hearing. The tensor tympani, which also helps dampen sound by tenseing the tympanic membrane, is innervated by the mandibular division of CN V, not CN VII. The malleus and incus are bones (ossicles) rather than muscles, so they aren’t innervated to produce a dampening action.