IV.C.6 Head: The Hearing Mechanism Page 4 of 4

	Can you find the tensor tympani muscle?
It is the muscle that connects to the malleus at the tympanic membrane in this drawing:
	What is the function of the tensor tympani muscle and what nerve innervates this muscle?
This muscle is innervated by the mandibular branch of the trigeminal nerve (V3). This muscle functions to tense the tympanic membrane and decrease the effect of loud noises.
	When would these muscles be most useful to you?
A rock concert.

There are four cranial nerves that carry pre-ganglionic parasympathetic fibers:

• Oculomotor nerve CN III which supplies the ciliary ganglion.
• Facial nerve CN VII which supplies the submandibular ganglion via the chorda tympani and the pterygopalatine ganglion via the greater petrosal nerve.
• Glossopharyngeal nerve CN IX which supplies otic ganglion via the tympanic plexus and the lesser petrosal nerve.
• Vagus nerve CN X which supplies pre-ganglionic parasympathetic fibers to the foregut and the midgut. Note that the hindgut is supplied by the parasympathetics of the lumbosacral plexus.

	Which of these nerves transverse the temporal bone?
The chorda tympani, greater petrosal and the lesser petrosal nerves.