What cranial nerve innervates the stapedius muscle?

The stapedius muscle, the smallest skeletal muscle in the human body, is primarily responsible for dampening the vibrations of the stapes bone in the middle ear. This action helps to protect the inner ear from loud sounds and contributes to regulating sound transmission.

Cranial nerve 7, also known as the facial nerve, innervates the stapedius muscle. This innervation is critical because, when the stapedius muscle contracts, it pulls the stapes away from the oval window of the cochlea, reducing the intensity of sound that enters the inner ear. This function is especially important in preventing damage to the sensory cells in the cochlea from excessive acoustic stimulation.

Consequently, the proper functioning of the facial nerve and the stapedius muscle is essential for maintaining auditory health and protecting hearing mechanisms. The association of the stapedius muscle with cranial nerve 7 reflects the nerve's broader role in motor control of facial expression and other functions.