Now, let’s take a look at the maculae that are found in the saccule and the utricle. The maculae contain hair cells.
Associated here on their apical region are some structures that are referred to as otoconia.
These overlie the hair cells that are shown down in through here. So, what will happen with respect to,
let’s say, linear acceleration is that when you run forward and you are accelerating, the otoconia have much
more inertia than does the endolymph. As a result, the otoconia will stay in place and the endolymph
will cause movement that will bend the hair cells that are right along here causing depolarization
or stimulation of those hair cells. This will then initiate synaptic transmission of the afferent nerve fibers
of the vestibular component of cranial nerve number eight, the vestibulocochlear nerve. We also have
hair cells in the semicircular canals. These are associated with the crista ampullaris. The crista ampullaris
is characterized by the cupula, a very prominent body associated with the crista ampullaris. Here are the hair cells.
In this simplified drawing, you see one hair-like extension of these sensory hair cells. In reality, there’ll be
numerous stereocilia which define this hair-like extensions of the apparatus. What will happen here with
angular acceleration is, let’s say, you’re moving to the right. You’re rotating. You're pivoting. What will happen is
the endolymph has greater inertia than does the cupula. So the endolymph here will push the cupula in this
direction causing bending of the hair cells and depolarization along the afferent nerve fibers associated
with the vestibular nerve. So, this will result in synaptic transmission of those afferent nerve fibers.