# The Anatomy of the Organ of Corti Will Styler - LIGN 113 --- ### Today's Plan - The Organ of Corti - The Journey of Sound ---
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--- ### The Basilar membrane moves with sound - Tonotopically!
--- ### Vibration doesn't matter unless we can detect it - We need to 'transduce' the sound from kinetic energy to electrical energy - That's the role of the organ of corti! ---
--- ### The Organ of Corti Functions - *Amplify* sound further - *Transduce* sound from kinetic to electric energy - *Transmit* that energy to the brain --- ### Structures within the Organ of Corti
--- ### The structures we care about - Dieter and Hensen Cells - Tectorial Membrane - The Stria Vascularis - Outer Hair Cells (OHCs) - Inner Hair Cells (IHCs) - 8th Nerve --- ### Deiter's ('Phalangeal') Cells - Provide structural support for the OHCs - Not super interesting!
--- ### Hensen's Cells - These have some small physiological roles - They show promise for future research, but we mostly don't care
--- ### The Stria Vascularis
--- ### The Stria Vascularis - Produces Endolymph - Has specific cells dedicated to transporting K+ ions into the endolymph - More on this later - This is amazingly important --- ### The Tectorial Membrane
--- ## The Tectorial Membrane - Surprisingly poorly understood --- ### "Wait, why don't we understand how this works?!" - The Cochlea is a little tiny structure - Embedded in bone - Inside a human's head - Godspeed, researchers --- ### The Tectorial Membrane - [Seems to play a role in frequency specification and amplification](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2856508/) - Not a great thing when it's missing - Outer hair cell tips are inside the tectorial membrane - ... but not inner hair cells --- ### Only the tips of the OHCs are embedded in the Tectorial Membrane!
--- ## The Outer Hair Cells
--- ### Outer Hair Cells - The Outer Hair cells help to *amplify* motion of the basilar membrane - The cell's length shifts in harmony with the sound - Preferentially amplifies quiet sounds ---
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--- ### The Outer Hair Cells form the 'cochlear amplifier' - They're connected to the tectorial membrane - They help us a *lot* in hearing --- ## The Inner Hair Cells
--- ### Inner Hair Cells - Inner hair cells transduce vibration into electric potential - These are a *crucial* element of the chain ---
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--- ### Inner Hair Cells are the last link! - They turn basilar membrane vibrations into nerve signals - We'll talk about how in physiology! --- ### Inner hair cells are directly (and richly!) connected to the nervous system - IHCs are connected to the Spiral Ganglion - They transmit a train of pulses down the nerves ---
--- ### The Sprial Ganglion connects to the cochlear nerve
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--- ## The Cochlear Nerve - Also known as the 'Eighth Cranial nerve' or the 'Auditory Nerve' - Splits off from the 'Vestibulocochlear Nerve' ---
--- ### The Vestibulocochlear Nerve connects to the Pons
--- ### ... and finally, sound has reached the brain! - In a format it can understand - The rest is physiological awesomeness --- ## The Journey of Sound ---
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--- ### A few teaser questions - "Wait, how do hair cells on top of a membrane trigger nerve firings?" - "If nerves only send pulses, how do we capture gradient changes in amplitude?" - "Why do chemicals which build up in the stria vascularis lead to **profound** hearing loss?" - "Wait, how the heck do you replace the entire organ of corti with an implanted device?" - ... and how do you install it!?! - **All this and more, later in LIGN 113!** --- ### Next time - It's on to sound! ---
Thank you!