A review of neurogenic control of the tympanic membrane on the 4th of July.
The human ear and tympanic membrane allows for hearing over a wide range of sound. Two cranial nerves moderate the function of the tympanic membrane when exposed to loud noise, which is known as the acoustic reflex.
A branch of the facial nerve innervates the stapedius muscle. When exposed to loud sound, it contracts the stapes bone in the middle ear, decreasing sensitivity to loud noise. You can see this in action in patients with peripheral facial nerve palsy. These patient’s may complain of increased sensitivity to a sudden hand clap or other loud noise on the affected side.
And, the tensor tympani nerve, a branch of V3 the trigeminal nerve, innervates the tensor tympani. It also works to damp down loud noise, but typically is less noticed than dysfunction of the facial nerve.
TIP: S’s and T’s go together – the seventh nerve controls the stapedius, the trigeminal nerve controls the tensor tympani.