Inner ear transduces ____ to _____
Mechanical energy to Bioelectric code
How is signal transduced?
- Motion of stapes moves structures of IE
- This motion causes the hair cells to be stimulated at elicit neural discharges in auditory nerve
The inner ear provides 3 pieces of info about the sound:
- Frequency
- Intensity
- Temporal content
Three structures of the IE
- Semicircular canals
- Vestibule
- Cochlea
Semicircular canals
Represent X, Y, Z planes so your head knows what direction it’s in at all times
Tell you when you’re moving
Know; anterior canal, lateral/horizontal canal, and posterior canal
Vestibule
Between semi. canals and cochlea
Contains oval window
Cochlea
Winding organ w/ 2.75 turns
Decreases in diameter from base (biggest where stapes is)
35mm total length
Membranous labyrinths
- located w/in bony labyrinths
- chemical differentials allow for diffusion
- contains endolymph (mostly K, less Na)
Bony labyrinths
- contain perilymph (similar to CSF)
- Mostly Na, less K
Membranes connected to the cochlea are….
Oval Window and Round Window
Important for compression
When you push into the oval window, the round window bulges out, and vice versa
3 Tubes in the Cochlea
- Scala media (middle tube)
- Scala vestibule (top tube)
- Scala tympani (bottom tube)
Reissner’s membrane
- separates the scala media from scala vestibule
Basilar membrane
- separates scala media from scala tympani
- on bottom of scala media
- auditory nerve formed off the ganglion
- gets wider as you move from base to apex of cochlea (opp of cochlea!)
- lower freqs resonate best at apex (floppy)
- higher freqs resonate best at base (stiffer)
Organ of Corti
On BM
Contains OHCs and IHCs
Inner hair cells
- 1 row of 3000
- send signals TO brain
- shaped like jugs
- 50 sterecilia on top
- tips of stereocilia NOT embedded in tectorial membrane
- arranged in straight line
Outer hair cells
- 3-5 rows of 12,000-15,000
- take signals FROM brain
- shaped like test tubes
- 100 stereocilia on top
- tips ARE embedded in tectorial membrane
- arranged in U or W pattern (connected w/ tips)
