The Reason Ears Were Invented. The original function in evolution? ….Equilibrium, coordination and balance. The VESTIBULAR APPARATUS : This is where we find Equilibrium Receptors. Like the hearing “apparatus” in the cochlea the VA has HAIRS too.
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The hairs work a little differently but the result is the same we get TRANSDUCTION: this time we will transduce motion into nerve impulses.
Membrane contains otoliths (calcium carbonate)
hair cells move against it
Utricle more sensitive to horizontal movement,
saccule to vertical
Semicircular canals arranged at right angles
to each other
Each has an ampulla in which hair cells are located
hair cells move against endolymph
utricle- head movement away from vertical
saccule- head away from horizontal
Semicircular canals- rotational acceleration
(maintain balance while turning)
Receptors for equilibrium- “hair cells”
Cell membranes are depolarized when bent,
the CRISTA AMPULLARIS
The Crista ampullaris consists of a gelatinus cap called the cupulaROTATIONAL Equilibrium
(any level above 80 decibels will damage the organ of corti)
Some antibiotics make ears more susceptible to damage ( OTOTOXIC) streptomycin, kanamycin, gentomycin