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potential in the hair cell which releases a neurotransmitter to sensory nerves, whose axons
make up the auditory nerve, which sends an action potential to the brain
The basilar membrane is thicker and stiffer at the base and wider and thinner at the end
o High frequency waves cause flexion at the basal end
o Low frequency waves cause flexion at the apical end
The vestibulocochlear nerve transmits action potentials stimulated by mechanoreceptors
at different positions along the organ of corti to the brain’s auditory cortex
Conduction deafness is caused by the loss of function of the tympanic membrane and/or
ossicles
o Caused by scarring from infection or stiffening with age
Nerve deafness is caused by damage to the inner ear auditory pathways
o Damage to hair cells (tinnitus) by exposure to high volume
Hair cells in vestibular system detect the position and movement of the head
o Vestibulocochlear reflex allows you to stay focused on something even if you
move your head
Vestibular system consists of 3 bony semicircular canals and the vestibule

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Semicircular canal has a membranous semicircular duct where fluid shifts when
the head moves
§ Oriented differently so the fluid moves differently when you move your
head and the brain can detect how your head is moving
§ Cupula projects into the base of each duct and bend stereocilia, causing a
graded potential
Vestibule has membranous saccule and utricle
§ Stereocilia are bent in different ways and embedded in gelatinous
membranes that contain otoliths
• Otoliths are calcium-like stones that move in accordance to inertia



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